Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on January 10, 2013, 03:22:08 pm
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Just aquired a 4x10 5D6A without the speakers. Have 2 of the jensen bell covers. Tube chart perfectly intact. Im starting to get sick to my stomach. Same customer from last night on the 1959 5E3. I noticed when i was blowing it out that it has two 5U4 rectifier tubes. All tubes are CBS. Face plate lettering is very good. What the hell is going on here? He says he has more as well later.
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And why is the tweed ripped off all of them? :laugh:
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Not a clue on the missing tweed for last 3 amps i have had here. I didnt own that Super Amp but i sure as H own these. I feel quilty all of a sudden. My friend found a 1966 Princeton 3 months ago painted blue and pink. Go figure. Is this amp a more desirable one? Have never own either of these amps.
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It would be among the first narrow-panel Bassman amps. Strangely, we don't have a schematic for it on the site. It would be interesting to get you to compare it to the 5E6 Bassman schematic (http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_5E6.pdf) to see what the differences are.
Every tweed Fender is gonna be desirable to some degree. I think folks are a little too fixated on the 5F6A, but that may be largely an issue of tinkering tone circuits until Fender landed on what players liked best.
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I would be among the first narrow-panel Bassman amps. Strangely, we don't have a schematic for it on the site. It would be interesting to get you to compare it to the 5E6 Bassman schematic (http://www.el34world.com/charts/Schematics/files/fender/BASSMAN_5E6.pdf) to see what the differences are.
Every tweed Fender is gonna be desirable to some degree. I think folks are a little too fixated on the 5F6A, but that may be largely an issue of tinkering tone circuits until Fender landed on what players liked best.
Found schematic online. Was sorta hard to find it.
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.
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First glance looks pretty much the same as the 5E6
Cathodyne inverter.......and 12AY7 in V1 & V2, dual recto, 10Meg local feedback....wow, 2 gain stages, CF, then another gain. I'll wager that thing rocks!
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thanks for the schematic.
I have speculated what the the circuit looked like.
Any word on what the transformers and choke are?
FYI, There was an individual who was making a copy of the 5D6 based on chassis #0035. adding some extras calling it a 5D6B. the amps were retailing in the $2000 neighborhood.
Given the rarity of the amp, can you verify the PI.
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Plexi, once you get it up and running, it would be nice to see some voltage readings. Man, you got all the luck. Great deals you`ve had lately.
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Plexi, once you get it up and running, it would be nice to see some voltage readings. Man, you got all the luck. Great deals you`ve had lately.
Yes i will make note and supply you with the voltage specs. I have tested all the tubes and they are very good. CBS BP 6L6GC's. Power transformer is working. Filament voltage is good. B+ is 440VDC from rectifier with no load. Standby switch bad. Bypassed and no plate voltage through OT. Suspect choke. Will jump with 500 ohm resistor tommorow and see after checking choke. Might check tonight if i can catch my breath. Im wiped/
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Standby switch bad. Bypassed and no plate voltage through OT. ...
The standby switch appears to have a cap to ground, according to the schematic. Don't know if it's present in your amp.
If it's there, that cap might be leaky and dragging the voltage down. Try unsoldering at the switch itself.
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Standby switch bad. Bypassed and no plate voltage through OT. ...
The standby switch appears to have a cap to ground, according to the schematic. Don't know if it's present in your amp.
If it's there, that cap might be leaky and dragging the voltage down. Try unsoldering at the switch itself.
Yes i was looking at that. The cap is present. There is no continuity on standy with DVM in either position but are going to there respective points in the circuit. Also it would have helped if i had looked closer at the PS caps. Removed tham and tested on analog. Dead saturated shot. The choke is measuring 61 ohms.
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The choke is probably fine.
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YEAH, you guy's seem to snag all the good finds. :thumbsup: :thumbsup:
Just slightly off topic, the "cathodyne inverter" if i have got it right is in a lot of fender amps and not something new, any fors and against useing these inverters. They seem to be in alot of the early models and LTPI are more common these days.
Also with a 12A_7 PI drawing ~10mA of current, what would this type of inverter likely to draw in the current department.Thanks
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http://www.valvewizard.co.uk/cathodyne.html (http://www.valvewizard.co.uk/cathodyne.html)
Some info on the cathodyne. Merlin has info at the end on how to improve performance (not recommended in a vintage amp, but helpful in a new build). There is even more info in his new preamp (second edition) book.
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Man i bet this thing rocks too. Werent we disscusing this amp a few months ago in another thread? Something about the differences if any in the 5D6 & 5D6A?
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Man i bet this thing rocks too. Werent we disscusing this amp a few months ago in another thread? Something about the differences if any in the 5D6 & 5D6A?
Well then, let's discuss some more rare birds, then maybe more will turn up! :icon_biggrin:
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Back from Dr Extraction place. Going to take the best detailed pics i can get from my camera. I think the PI was of main concern but will get the preamp as well to see if it matches the schematic. Back in a bit/
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Ok. Here is part verification as to what is in my 5D6A. Let me know if i missed something.
Pics from top to bottom seperated are:
PI V3
V2
V1
(http://i356.photobucket.com/albums/oo5/plexijtm45/PI.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/V3Pin651KReads55K.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/220KBiasCoupling.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/V2Socket.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/V1VDEct.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/V1Plates.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/V2Cathodes.jpg)
(http://i356.photobucket.com/albums/oo5/plexijtm45/V2Socket.jpg)
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PI seems odd...
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PI seems odd...
Both resistors are color banded 51K. No color fade on this end. One reads 54K & 55K
There in circuit so that sometimes makes readings off a hair. 51K is an odd number. Maybe they are or were 56K and mis printed.
Even so the resistor would drift up in value instead of lower in value i think
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Man i bet this thing rocks too. Werent we disscusing this amp a few months ago in another thread? Something about the differences if any in the 5D6 & 5D6A?
Again I post, that for those interested in the 5d6 circuit there are disassembly drawings of a 5D6, (sometimes referenced as a 5d6 DL), Some of the obvious differences are:
1. the location of the 100 ohm resistor on V2 tube between the two plates. the 0035 has the resistor on the board rather than on the tube socket.
2. Rectifiers are 5y3's rather than 5u4's
3. The transformers are 7926, 2770, and 14560 for the p/t, o/t and choke respectively.
4. The p/t reportedly does not have a bias tap, but has a 100 ohm resistor from the opposite HV secondary
5. B+ voltage about 400
6. The p/t is apparently small enough that the paper separating the windings is discolored, (I interpret this as a high sag application)
I am in the process of reviewing the pictures to identify resistor values. (To me its a slow process, since I keep forgetting the color codes. Once I am done, I will post the layout and schematic on this forum.
Comparing the 5d6a circuit and the 5e6a circuits, I noticed three resistor value differences.
1. on the bias circuit 6800 v. 3300 upstream of the diode.
2. on the bias circuit r-c ground, 47k v. 56k.
3. On the cathodyne PI, B to plate 47k v. 56k.
Without knowing what transformers are included on the 5D6a, the numbers above appear to be meaningless.
Web page showing 5d6 disassembly: steelguitarforum.com/viewtopic.php?p=1397040
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Pics of any and all part numbers. Chassis code matches tube chart numbers. The only numbers on the OT are shown. The PT has faint and hard to read codes. The logo has disintergrated from the top of the PT. I assume TRIAD? The choke has no numbers period. The tube sockets have etched script for the tubes used in the preamp,power and rectifier tubes on the chassis.
The preamp tube arraingement is in reverse on the etched script on the chassis from the tube chart.
Chassis etching = 12AX7-12AY7-12AY7. Tube chart = 12AY7-12AY7-12AX7
This had to have been done when it was being designed. I cant picture anyone even being able to see the etching unless you had the chassis out of the cab and on a bench
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Man i bet this thing rocks too. Werent we disscusing this amp a few months ago in another thread? Something about the differences if any in the 5D6 & 5D6A?
Again I post, that for those interested in the 5d6 circuit there are disassembly drawings of a 5D6, (sometimes referenced as a 5d6 DL), Some of the obvious differences are:
1. the location of the 100 ohm resistor on V2 tube between the two plates. the 0035 has the resistor on the board rather than on the tube socket.
2. Rectifiers are 5y3's rather than 5u4's
3. The transformers are 7926, 2770, and 14560 for the p/t, o/t and choke respectively.
4. The p/t reportedly does not have a bias tap, but has a 100 ohm resistor from the opposite HV secondary
5. B+ voltage about 400
6. The p/t is apparently small enough that the paper separating the windings is discolored, (I interpret this as a high sag application)
I am in the process of reviewing the pictures to identify resistor values. (To me its a slow process, since I keep forgetting the color codes. Once I am done, I will post the layout and schematic on this forum.
Comparing the 5d6a circuit and the 5e6a circuits, I noticed three resistor value differences.
1. on the bias circuit 6800 v. 3300 upstream of the diode.
2. on the bias circuit r-c ground, 47k v. 56k.
3. On the cathodyne PI, B to plate 47k v. 56k.
Without knowing what transformers are included on the 5D6a, the numbers above appear to be meaningless.
Web page showing 5d6 disassembly: steelguitarforum.com/viewtopic.php?p=1397040
100K Ohm on V2. I think a year or so ago Steve told me not to handle or play with the Selenium rectifier too much. I have to read up on selenium and see what selenium really is. Might be good with captain crunch!
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Any word on what the transformers and choke are?
I'm guessing the choke is DC rated for 200mA. Same with the HT winding on the PT. Just guessing.
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This had to have been done when it was being designed. I cant picture anyone even being able to see the etching unless you had the chassis out of the cab and on a bench
maybe this one was a prototype?
--DL
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This had to have been done when it was being designed. I cant picture anyone even being able to see the etching unless you had the chassis out of the cab and on a bench
maybe this one was a prototype?
--DL
Thats what i have been thinking. The info i have dug up is this:
5D6A Introduction Date:
The 5D6A was introduced in March 1955 with number 0100 and continued up through the 5E6
Bassman 5D6, 5D6-A (tweed)
0600 to 0900 - 1954
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51K is an odd number.
Not really, plexi, 51K is a normal value in 5% resistor land, just like 10K, 15K, 18K, 22K, 27K, 33K, 39K, 47K, 56K, etc are the normal values in 10% resistor-land.
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PI seems odd...
Both resistors are color banded 51K. No color fade on this end. One reads 54K & 55K
There in circuit so that sometimes makes readings off a hair. 51K is an odd number. Maybe they are or were 56K and mis printed.
Even so the resistor would drift up in value instead of lower in value i think
Maybe they both measured about 50k at the time of installation?
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The changed font for the "47k" in the schematic posted above suggests it was a later addition to the schematic.
That font looks familiar, probably from Dave Funk's Tube Amp Workbook (my copy is in another state).
50k was probably the typical value at the time, with 47kΩ being the later edited value when the schematic copy was printed (probably in a book).
Maybe they were out of 50kΩ (or 47kΩ if that was truly the correct value) that day, and used 51kΩ to get the amp built. Each of those has the gold 5% tolerance band, and I can't remember ever seeing a resistor in a vintage fender amp of tighter tolerance than 10%. So I think that value was unique to this amp (or others made that day/week), and swapped to get 'r done.
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I was going through the layout on the posted website. I noticed that a ground and a 220K resistor were not shown in the pictures. On the 5D6a layout, this would appear between the 10 meg resistor, and a node branching to a cap and another 220K resistor found in the tone stack.
I am not sure how much the chassis was stripped, because I couldn't find in any of the pictures the 1 meg resistors shown at the jacks. (Builder beware!!!)
Regarding the selenium diode. Replace with a silicon diode. Failure of the diode to heat, results in poisonous gases being produced.
This is shot of the updated 5D6b circuit board. http://bb.steelguitarforum.com/viewtopic.php?t=167347&postdays=0&postorder=asc&start=0. (http://bb.steelguitarforum.com/viewtopic.php?t=167347&postdays=0&postorder=asc&start=0.) It does not show the 220K resistor as discussed above.
Also, the 5D6 seems to have pin 9 grounded to the chassis. (Easy upgrade)
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Interesting thread. Do i need to store my amp in a walk in safe? I can wait to finish the 5E3 cab so i can start working on the 1954 5D6A
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I was going through the layout on the posted website. I noticed that a ground and a 220K resistor were not shown in the pictures. On the 5D6a layout, this would appear between the 10 meg resistor, and a node branching to a cap and another 220K resistor found in the tone stack.
That is the horizontal 220k in picture 5, reply #18 of this thread.
I am not sure how much the chassis was stripped, because I couldn't find in any of the pictures the 1 meg resistors shown at the jacks. (Builder beware!!!)
They are mounted directly on the jacks in Fender amps, and we don't have any closeup photo of the input jacks in the inside of the amp. I'll bet you $100 they are there.
Regarding the selenium diode. Replace with a silicon diode.
Probably a good idea, but the selenium rectifier drops some voltage, at least more than a silicon diode. As a result, you may have to tinker the resistors in the bias circuit to land back on your desired bias voltage.
Also, the 5D6 seems to have pin 9 grounded to the chassis.
The few close-up shots of a tube socket in this thread show 2 filament wires, and pin 9 of preamp tubes not grounded. The overall shot also shows 2 wires for the pilot light.
However, the one-wire filament circuit was dead-nuts common in mid-50's Fenders. They generally grounded one filament pin of each tube to the chassis near the socket, grounded one of the pilot light terminals to its mounting bracket and grounded one side of the filament winding at the PT along with the high voltage center-tap.
But if this amp does have a filament center-tap as indicated in the schematic, then they would have used a two-wire filament circuit.
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Interesting thread. Do i need to store my amp in a walk in safe?
That guy seems to be hyping things a bit, maybe to make his hand-built amps look like a bargain by comparison.
There was a guitar shop in Nashville that had an all original 5F6A Bassman in quite excellent condition that had been owned by Luther Perkins (guitarist for Johnny Cash), along with a signed letter from Perkins that confirmed the serial number and the he indeed owned and used the amp. I think they wanted $4k (maybe slightly less), and that was with the provenance linking the amp to a famous player.
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Un-Real!!!! Well all I say is both these vintage amps fell in good hands to become even better than they were in their original state. I will be looking forward to following their restoration progress. BTW-have you established their approximate year of manufacture??
Platefire
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The pots are dated 1954. Selenium rectifier dated 1954. The OT i dont know what the date code TRIAD 2485 means yet. Pics of 1 megs,220k.
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Wow! That when I started the 1st grade. :embarrassed:
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CT's Grounded. Preamp and power tube filament wiring
I am in the first grade, Starting all over again. This is the proof! :laugh:
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The selenium rectifier in that very low current bias circuit is likely to never be warmer than room temperature. It's already lasted +50 years and will likely be still working after another 50 years. That one is tiny enough that it's not much of a threat, especially in that circuit. I would leave it be if the bias voltage is what you expect. Like HBP said, you'll have to mod the bias circuit if you replace it with a silicon diode.
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Im keeping all that i can stock. I have not gotten around to checking all the resistor values. Maybe i will do that later today to get that out of the way. Not certain yet on the health of the coupling caps. I have some yellow Jupiter Astron style caps im going to put in the 5E3. Im ordering the Jupiter Astron style red caps for this amp. Those Astrons are known leakers and after 59 years im sure they wont mind. Nothing lasts forever/
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FYI,
I was comparing a 5d6, with serial number 0035 to the 5d6a which is the topic of this thread. A comparison of layouts between the 5e6 and the 5d6a has been discussed. As I have discussed there are some minor differences between
5d6a and 5e6s. Maybe this is not the thread to discuss the 5d6, as I may be confusing this threads discussion.
Basically, I just saying, I believe there are some major differences between the 5d6 and 5d6a, where I am suggesting two links to review what work has been done on a 5d6 with a stamped serial number of 0035.
Regarding my ability to find missing 1 meg resistors, I won't take that bet, because, I expect them to be there. The clarity of the photographs, I have downloaded is not that good. I am going pixel blind from zooming.
Regarding pin 9 (12a_7's) on chassis 0035 being grounded to the chassis; from the solder traces shown, other pictures from the steelguitar forum, and a review of Fender D schematics, I feel comfortable that chassis 0035 was assembled with the pin 9 grounded.
Given that the Bassman was being upgraded to support Leo's new bass guitar, Improvements on the 5d6a seem reasonable.
To avoid other confusion, I start a new thread on a comparison of a possible 5d6 circuit and the 5d6a circuit.
This thread, has provided me some information, I had speculated about, and shot down other speculations.
Thanks guys.
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Cleaned the tube panel side down and sockets. Final clean of transformers. Light steel wool and WD on iron laminates. Dam that front panel looks like it was just made
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Very, very nice. Thanks for the pix, too!
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Talk about manic! I have this NASCAR wax cleaner called fastwax. Comes in spray cans. Killer stuff.
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Final clean of transformers. Light steel wool and WD on iron laminates.
Isn't WD-40 is conductive? Or was it just that it displaces moisture? :think1:
Iron looks great now for it's age.
Interesting to note that the PT has a copper band around it that far back in Fenders line.
Brad :icon_biggrin:
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Final clean of transformers. Light steel wool and WD on iron laminates.
Isn't WD-40 is conductive? Or was it just that it displaces moisture? :think1:
Iron looks great now for it's age.
Interesting to note that the PT has a copper band around it that far back in Fenders line.
Brad :icon_biggrin:
I just lightly wiped WD on with a rag. I didt spray on the transformers them selves. Definatley going to be great when the cab,speaker and chassis are completed
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> Isn't WD-40 is conductive?
Zilch for all practical purposes.
One of the few good uses for WD-40 is *temporary* drying/sealing damp ignition wires. It does tend to displace water, and does NOT bleed-off the spark.
It's kerosene. Very selected fraction of all the stuff sold as kerosene, but just petroleum distillate.
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I have been looking at several 5D6 bassman pics and found a 47M & 100K resistor coming off the 270K voltage dividers in the pic below. The 5D6A has a 10M & 220K combination. Cant verify the 5D6 feedback resistor yet. Im thinking it is 20K as is the 5D6A. It's in hiding just under the last PS cap pic. Still looking for differenced between the 5D6 & 5D6A
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found a 47M & 100K resistor
That's really a 4.7M. A 47M would be yellow/violet/blue.
Still looking for differenced between the 5D6 & 5D6A
Why? Didn't you say your amp is a 5D6A?
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found a 47M & 100K resistor
That's really a 4.7M. A 47M would be yellow/violet/blue.
Still looking for differenced between the 5D6 & 5D6A
Why? Didn't you say your amp is a 5D6A?
I misinterpeted the last band (green)
Yes my amp is the 5D6A. Maybe i should have started another thread on 5D6. Just curious what the differenced are between the cicuit boards
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I have been looking at several 5D6 bassman pics and found a 47M & 100K resistor coming off the 270K voltage dividers in the pic below. The 5D6A has a 10M & 220K combination. Cant verify the 5D6 feedback resistor yet. Im thinking it is 20K as is the 5D6A. It's in hiding just under the last PS cap pic. Still looking for differenced between the 5D6 & 5D6A
Good luck, determining the differences. Regarding the feedback resistor, I hope you have better luck than I have. The only recommendation is to look at 5d6b chassis that are on a couple places on the internet. The poor photos I have suggest that the resistor might have a green or first blue stripe.
Plexi, do agree, that there is no 220K resistor between the 10meg and ground?
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I do agree. There is no 220K between 10M and ground. Does the missing 220K equate to less gain? If you blow the picture up real big you can see a faded red-black,orange for the feedback resistor which would be 20K.
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Got the 5D6A recapped today with all Sprague capacitors. Not cheap for sure. Sounds pretty good to my ear drums on my bench testing 2x12 ext cab. Waiting for the red Jupiter Astron style tone caps to arrive. My camera is biting the dust. :worthy1: :worthy1: :worthy1: :worthy1:
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Looking real good Plexi.
What's that great big cap on the far left end of the eyelet board? That's not the cathode bypass cap is it? 250uF@6v?
Have you used the Jupiter Astron caps before? If so how do they sound to you?
Brad :icon_biggrin:
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250uf sprague bypass cap inside sleeve. I have the yellow Astron style un my 5E3. They sound very good to me. Full and warmy. Not brittle or muddy. Real vintage tone. If i keep the amp 6 months or more the caps will form there carbon path. Though that probably takes a year or so for a new tone cap to mature. Tone just gets better over time. I wish i had the original Astron power supply cap sleeves. I would have used the sleeves as and tucked each new Sprague inside. The 100uf bias cap is inside the amps original 100uf sleeve
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I was taking more pics tonight to try and make out what the pencil script is on the tube chart. Then i saw the number 54 next to the chart in some kind of old magic marker or whatever they used. Now look real close at the pencil script on the tube chart. Im seeing
lf 1rst. Im trying to make out a name and cant put one together. So i am seeing lf 1rst. I know way back then they used to abbreviate the first of a product sometimes by using 1rst instead of (the first). And i believe with my eyes i am seeing lf before and seperated by 1rst. Maybe Kirst?
Say im not going mad! Please. Say it aint so. :dontknow:
Also if you look at the numbers 5D6A on the tube chart you can see another letter or something to the right of the A before it was stamped. Maybe just goo?
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Looks like K maybe not If?
Brad :icon_biggrin:
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I read first...
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k i r s t
--DL
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You're not thinking that handwriting means it's the first 5D6A to roll off the line???
Here's another likely scenario... Look at how it's written next to the tube placement chart. I think someone later wrote it there to indicate that the 5U4 is the 'first' tube in the line up.
The date code stamp "EC" would indicate 1955, third month.
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Oh no not the first or anything like that. I was coming up with all kinds of interpetations as to what that pencil script was. The serial number has some meaning as to which number it was that rolled off the AL. Ive seen a lot of info online and it is all different as how to interpet the serial number. So at the moment i havent had time to break that down or know which info i am seeing online that is correct. In any case a once in a lifetime find for me. Got the red Astron style Jupiter caps installed tonight. Will plug and check all voltages in the morning
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Got the red Astron style Jupiter caps installed tonight. Will plug and check all voltages in the morning.
What!!!! Dog gone you Plexi! :cussing:
Now we gotta wait untill the morning to for you to tell us how that amp sounds????? :BangHead: :cussing:
Brad :laugh:
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Yeah man im pretty wiped out. Im going broke buying those jupiter caps. $85.60 for the six of them. The amp deserves the best so i got to do it right. Im going to eat breakfast now!
396VDC plates with -43VDC grids
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Voltages taken after 30 minutes warm up. Tryong 12AT7 tubes as i dont have any 12AY7 at the moment. :worthy1: http://www.el34world.com/charts/valve/ValveData.php?e=view&f=14699 (http://www.el34world.com/charts/valve/ValveData.php?e=view&f=14699)
Edit: Voltages were taken again with 12AY7 V1 & V2. Voltage chart updated.
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That '55 fender is a real prize plexi! love almost anything from 1955 including Chevies with a modified V8 under the hood. lay scratch in 2nd and 3rd gear cruisin' past the malt shop....old guy's fun
:icon_biggrin:
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Nice tone machine. :worthy1:
What? That's it? :m13
Brad :laugh:
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SIR Willabe & Smackoj i couldnt be happier. (got a winning lottery ticket?)
Well i stole the 12AY7's from the 5E3 to test the tone difference in this bassman. I went back over and changed the tube chart voltages to what they should reflect on the schematic. Close enough. Wow! The amp definatley sounds sweet with the 12AY7's in V1 & V2. 12AT7 gain factor of 60 is too much in this amp. 12AY7 gain factor of 45 is the sweet spot. Now im lovin it. I hear another thing you can do is to change the 5U4G rectifiers out for 5Y3 rectifiers for an even more sweet spot. The PT for the 5D6 & 5D6A were the same. They used a 3300r bias resistor instead of the 6800r in it now using the 5U4G's. This is as far as i am going with the chassis. It's done and sounds great. No fiddling with 5Y3's or anything else. Man what a difference using the 12AY7's. My high gain days are over for the most part. Blues and low wattage is king for me. Next is to re tweed the cabinet and mount jensen P10R speakers. :worthy1: :worthy1: :worthy1: :worthy1: :worthy1:
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Well i stole the 12AY7's from the 5E3 to test the tone difference in this bassman. Wow! 12AT7 gain factor of 60 is too much in this amp. 12AY7 gain factor of 45 is the sweet spot.
My high gain days are over for the most part. Blues and low wattage is king for me.
That's great to hear Plexi. Glad to hear that all the hard work, love and care you put in that amp has paid off for you.
That amp after all was designed with the 12AY7, so it makes sense that it sounds great in there. I think distortion is overrated, but that's just me. I understand the need for sustain but.....
I bet that amp will rock if you can get the volume up to at least 6 or 7 even with the 12AY7 in it.
Brad :icon_biggrin:
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I am using a 2x12 cab to test the amp with so the tone will be heavenly when it is mounted in the cab using 4 10" jensen speakers. I love a good 4x10 cab
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Oh yeah! The distortion is very nice and ramps up slowly and evenly as you turn the volume up all the way to 12. Not all in your face at once.
Nice.
I bet that amp would be great for playin slide.
Brad :blob8:
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Im going to use my most unfavorite word i have heard in life. Im Confuuuuused. Heres my confusion:
Bassman 5d6a serial number info as i have found it says the folowing:
Bassman 5D6A (tweed)
0100 to 0200 = January-May/1955 = 5D6A
But mine has a serial of 0823 and tube chart with matching 0823 EI March 1955
All the parts in the amp are dated 1954. So whats the skinny on the serial number?
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I have 1 or 2 of those big Fender amp books, let me see if I can find anything in them that might help.
Brad :icon_biggrin:
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Ok, here's something. From Tom Wheeler's "The Soul of Tone, Celebrating 60 Years of Fender Amps".
Page 170 has a pretty good large (half page) photo of a well kept 5D6. But you can't really see the pot wiring. Caption under photo Say's; most should be 55's but the tube chart on this amp is stamped DL, which indicates Dec. 54 (0077). Say's there's another that is dated Nov. 54.
Book lists photo credit to John Peden.
You should try to get in touch with both of these guys. They might be able to help you or lead you to someone who can.
I'll look for info on serial #'s and dating.
Brad :icon_biggrin:
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Thanks Willabe. I have an Aspen Pittman volume 3 book. It has every amp and schematic in it except the early bassman amps. It starts at the 5F6A. There was so much going on back then that god only knows what the real info is on the 5D6 and 5D6A amps They could be a mixed bag of all of them for all i know.
All my parts are dated 1954. 0823 is the serial number which does not fall into any of the bassman serial# catagories. This is getting weirder by the minute/
I also read some where last week that the earlier Bassmans used a very thin baffle board and when certain bass notes were hit the baffle board and speakers would flex back and forth. This baffle board is very thin and measures 1/4" thick. Very thin
Found little EC stamps around the inside of the cab
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Found little EC stamps around the inside of the cab
That's probably where some assembly dip was testing the stamp for ink before actually stamping the tube chart. :l2:
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:l2: :l2: That makes sense. Does this make sense? 0823 / #82 off the AL. March (3) 1955?
Edit" I just found this Bassman amp dating on the Greg Gagliano Fender amp dating site. It says:
Bassman 5D6, 5D6-A (tweed)
0600 to 0900 - 1954
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Oh no not the first or anything like that. I was coming up with all kinds of interpetations as to what that pencil script was.
It might be the woman who wired your amp up.
I had a '55 Tremolux with a small piece of tape inside the chassis between the tube sockets, which let me know it was wired by Eileen. Maybe "Kirst"en wired up your amp. I didn't notice the piece of tape with a name in your chassis.
Does this make sense? 0823 / #82 off the AL. March (3) 1955?
No, because the number on the tube chart is simply the number that's already stamped on the chassis. I seriously doubt the chassis stamping was done at the end of the line; more likely when it was an empty metal shell.
Which means what I've always said: don't read too much into the serial numbers. It is commonly seen in Fender guitar serial number charts that some ranges of number overlap years and/or guitars have numbers which fall outside their supposed year range. Those charts are generally compiled by observation rather than a set of rules.
You're very much better off noting the two-letter date stamp and comparing that with other features in the amp. At least, that was the gold standard for dating tweed Fender amps when I got out of the vintage game in 2000.
Seriously, forget the frickin serial #'s because I never knew a dealer who put any stock in them (unless they were trying to reel you in and you seemed excited by a serial number). Nashville had a number of vintage guitar shops, and I went to a LOT of shows back before 2000 including a number of very large shows in other states (like the Chicago show, Dallas show, etc) both as a buyer and as help for some friends who were vintage dealers.
I hear another thing you can do is to change the 5U4G rectifiers out for 5Y3 rectifiers for an even more sweet spot.
Don't do that. If you need to tinker, yank a single 5U4.
I haven't found info to state when the 5AR4/GZ34 was introduced, but between tube data sheets and Fender schematics it seems to have come out some time around 1959.
This was a bass amp, and you didn't want sag when you played the low E on your Fender Electric Bass. The 5U4 had the highest current capacity and generally the lowest voltage drop of the 5v rectifiers before the GZ34 was available, and it seems Fender experimented using a pair of them to reduce the voltage drop (because a single 5U4 would handle the current requirements). Fender even used the mercury vapor 83 in the 5F6 Bassman to try to reduce sag even more; after the initial voltage drop a mercury vapor rectifier has very little voltage output change with changing current.
Given Fender used the European designation on its schematics and tube charts, I can't help but wonder if they had tubes pitched to them by the same Philips/Amperex USA folks that were selling ECC83's and EL84/EL34's to U.S. hi-fi manufacturers. Or maybe they were reading industry mags of the day and seeing other manufacturers using the Euro tubes.
I dunno, I guess you can use two 5Y3's, but low sag/hum was the intent of this amp series pretty much from the beginning.
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Thanks HBP for your wisdom. A little excited on this end to even have it sitting here. Wish it could talk. No tinker on this one. It's finished and needs to go back in it's wooden condo. I may pull a 5U4 later down the line when it is actually back in the cab with the 410 speakers to see if i can hear any diff. I didnt find that little piece of tape with a name on it like i found in the 5E3. All in all it is one clean puppy.
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I am glad you rebuilt that puppy. Its your amp, you try the 5y3's and the bias change if you want. If you remove that 220K resistor, tell us how it sounds. It would not surprise me that it has a different tone. :m7
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Under noraml amp circumstances i would remove the 220k going to ground,change the VD run off resistors from 10M/220K to 4.7M & 100K. But i cant bring myself to start mesing with this amp. The worst part is i may never know what the tone difference is and that in itself is a sin. I could do it and it would not look tampered with after i was finished. Thats the million dollar question: To tamper or not to tamper. It is beautiful.
Let look back in this thread on page one and see what Geezer had to say:
Cathodyne inverter.......and 12AY7 in V1 & V2, dual recto, 10Meg local feedback....wow, 2 gain stages, CF, then another gain. I'll wager that thing rocks!
Without tampering with the amp can we get an approximate idea of what the tone may be like by comparing the 10M vs the 4.7M local feedback and omitted 220K to ground? Smoother,More rounded,Less breakup,different kind of clean and breakup. The tone math may be endless unless actually heard
And lastly i just dont have an SM57 mic to make sound clips of any good quality. We all would want to hear the differences at 3-5-7-8-11 O'clock
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I have a power tube question:
The schematic says 6L6G tubes. Tube data says 360VDC max. Did Fender possably not print the power tubes 6L6GC on the schematic or layout ? I see a lot of these amps online using 6L6GC power tubes. They can handle much higher max plate voltage.
Those old coke bottle 6L6-G tubes have a tone all of there own
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The schematic says 6L6G tubes. Tube data says 360VDC max. Did Fender possably not print the power tubes 6L6GC on the schematic or layout ?
I think it's more likely that Fender 'ignored' the tube data.
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I think it's more likely that Fender 'ignored' the tube data
That make perfect sense. The Deluxe reverb is a good example of that using 6V6GT tubes rated at only 350VDC with 415VDC on there plates
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They could have started testing/shipping their amps at that point with 6L6GB's and wanted to use up the old tube charts.
Brad :icon_biggrin:
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They could have started testing/shipping their amps at that point with 6L6GB's and wanted to use up the old tube charts.
Brad :icon_biggrin:
CBS 6L6GB is what came with it when i got it. The date code on them is 6043
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Just found the choke number on the winding paper. Very hard to see and hell to get a decent pic of. But here it is. Choke # 14597
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I think it's more likely that Fender 'ignored' the tube data
That make perfect sense. The Deluxe reverb is a good example of that using 6V6GT tubes rated at only 350VDC with 415VDC on there plates
Or they asked RCA if it would work, and were given the thumb's up.
Remember, earlier data sheets had conservative ratings intended to second-guess your design as well as line voltage variations. Later Design Maximum ratings with higher ratings put the load on you to second guess your design and line voltage variation. The exact same tube would appear to have higher ratings under the later system.
And for the most part, plate voltage ratings appear to be about the closeness of pin spacing and the dielectric strength of the plastic in the base. An 807 has a higher plate voltage rating that 6L6GB just because the plate connection is at the top of the tube instead of next to the other pins. The guts are exactly the same as the 6L6 version.
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I am almost finished with the bassman. I bought 4 Weber alnico 10S speakers. What a long road*
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Waiting for the red Jupiter Astron style tone caps to arrive.
I saw a webpage intended for radio restoration folks, which showed how to take a modern part and encase it in either molding wax or epoxy to simulate the size, shape and appearance of old-style parts. Restoration guys tend to have no faith in the old parts (they know they almost universally fail over time), and go so far as to create the old labels to put on their simulated parts to ensure a radio looks 1930's-new again.
I'm thinking of getting a couple Jupiter caps just to cut them open and see if they're doing the same thing: using a modern (say, polyester film/foil) cap and just encasing it in a package to look like an old Astron.
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I'm thinking of getting a couple Jupiter caps just to cut them open and see if they're doing the same thing: using a modern (say, polyester film/foil) cap and just encasing it in a package to look like an old Astron.
Snake oil? Hmmmm....... Could be.
Brad :laugh:
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I'm thinking of getting a couple Jupiter caps just to cut them open and see if they're doing the same thing:
Makes you wonder. I remember a thread a few years ago about someone cutting open a Sprague Atom power supply cap and finding i believe something the size of an Illinois cap inside. Let me know if you really open one up.
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Lookin' great there plexi. You got some sound bytes?
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I'm thinking of getting a couple Jupiter caps just to cut them open and see if they're doing the same thing:
I remember a thread a few years ago about someone cutting open a Sprague Atom power supply cap and finding i believe something the size of an Illinois cap inside.
Sluckey did that. What's inside is even smaller than an Il. cap.
Brad :icon_biggrin:
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Speakers wired up. I have a good feeling about how this is going to sound with these 10" speakers.
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> asked RCA if it would work, and were given the thumb's up
Also: the data-sheet ratings cover ALL services. Military radio, broadcast transmitters. (Yes, broadcast and mil users were supposed to use different part numbers, but....) If a broadcast transmitter quits, it could be $1,000/hour of lost ad income. If a military radio quits many things can go real wrong.
Compared to that, the "importance" of a bar-band is very small. If the guitar amp quits, the barkeep runs the jukebox while the band calls-around for another amp.
It's like: can a One Ton truck carry 3,000 pounds? If it's one load of hogs 10 miles once a year, yes it can. If it is a brick delivery truck working 6 hours a day 300 days a year, a 50% overload will result in early and frequent break-downs. OTOH if a 1.5-Ton truck is a LOT more expensive, a low-cash operator may choose to overload a 1-Ton and replace bearings and gears every few months.
And in particular: original 6L6 had a 400V number, but they had trouble with the *base* breaking down. Later sheets showed 360V. Even after improved base materials came into use.
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Speakers wired up. I have a good feeling about how this is going to sound with these 10" speakers.
Just letting you know, that if they're new Webers, they'll need breaking in for a while. New Webers can sound a bit harsh straight out of the box.
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Speakers wired up. I have a good feeling about how this is going to sound with these 10" speakers.
Just letting you know, that if they're new Webers, they'll need breaking in for a while. New Webers can sound a bit harsh straight out of the box.
I have a 3/8 jack cord running from my stereo out that i plug into the input jack of an amp or to the speaker alone and just leave it on 8-12 hours everyday for a week.
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Very Very nice! I haven't been following the progress of this since you got it but today kind of caught up. Great Job! I'll never forget the first vintage bassman I ever heard back in the 80's at an outdoor concert. This guy was playing a tele and it just sounded awesome--it made a lasting impression on me. I love all the old fender factory history too. Something about a vintage fender amp that's pure Ameriacan/USA more than any other amp to me. I treat every ventage Fender that comes in my door with great respect. I know your proud of it, congradulations! Platefire
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Yes that looks tweed-tastic!
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I didnt think i would ever get it all finished. It will look even better in a few months after it gets a tan and some wear. And in a few weeks those speakers ought to be broke in good.
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wonderful restoration. looks awesome!
:icon_biggrin:
i hope you keep it...on the other hand, couldn't blame you if you flipped it.
--pete
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I will keep it for a while. But you never know cause i never know. Ya know?
I found the original handle but it is petrified and not really usable
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I will keep it for a while. But you never know cause i never know. Ya know?
I found the original handle but it is petrified and not really usable.
Maybe try rubbing a bit of leather rejuvinating oil into it over time
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Saddle soap may help.
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The handle is hard as a rock. Mummified. Hard to believe the faceplate is this clean. Weird*
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Try Lexol for the handle.
No need to be in a hurry.
It look this long to get that dry,
so it might take a week to soak in new moisture.
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Try Lexol for the handle.
No need to be in a hurry.
It look this long to get that dry,
so it might take a week to soak in new moisture.
I'll give it a shot. Like you say it's been this long and there is no hurry anymore. Getting old does that to you. Slow Ride/
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Beautiful amp Plexi.....something to be proud of and a great piece of history. I would carry it around with a 2 wheeler and leave the handle be....but that's just me
:icon_biggrin:
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Thankyou all for your help and watching this amp get reborn again. Birth weight is 40+ lbs. A whopper! :)
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Thankyou all for your help and watching this amp get reborn again. Birth weight is 40+ lbs. A whopper! :)
:laugh:
Looks beautiful too!
Brad :icon_biggrin:
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Plexi, I found something yesterday you might be interested in. :icon_biggrin:
Short version; read the blue. :laugh:
I read an old Guitar Player interview with Rory yesterday (http://jasobrecht.com (http://jasobrecht.com)) in which Rory says his tweed bassman was a 1955. :w2:
That would make it a 5D6 or 5D6-A now wouldn't it?
(dating info from "The Soul of Tone, Celebrating 60 Years of Fender Amps, by Tom Wheeler.)
Now wait a minute, hold the phone! This changes everything, well in my mind anyway. :m13
It's well known that Rory played through a tweed bassmen (and/or tweed twins) for many years. Yes along with AC30's, Marshall combos and even a Brown face Concert 4x10 for a while.
But "Irish Tour's" sound IS that amp (well either 1) with a rosewood neck strat. (Possibly with a range master duck taped to the top of his main amp. He did use a range master in his early days with his band Taste when he played an early AC30. I have several DVD's and on at least one of them for a brief second you can see a pedal(?) taped to the top of his tweed bassmen. I'll have to go through them all slowly again watching for this.)
But I always thought it was a 58/59 TB/TT, as I think almost every one did. :BangHead:
I'm a big fan of Rory Gallagher and Irish Tour Live is on my top 10 albums of all time. I saw him live at the Argon Ballroom in the winter of 75(?), it was just a couple of weeks after Howlin Wolf (50's Chess Records blues star) died and during one song just before he started his lead Rory ran up to the mic and hollered "this is for the Wolf" and took off into a blistering impassioned solo which included his version of Chuck Berry's duck walk. I can still to this day see it in my mind but that was why those of us who loved Rory's music, who were touched by it, were drawn to it and moved by it, his ability to mix raw soul/passion/emotion yet had the technique/skill and chops to pull it off, so it wasn't just bashing.
It was a long time ago but my friends and I were musicians and we would ALWAYS as teenagers in awe of the big boys would scope out what gear was on stage with great intent as far as what we understood at that point. (I remember seeing an English band at the Argon and the lead guitar player had a red "Park" amp head! We looked at that up on stage sittin on a speaker stack and looked at each other and nobody new what it was. :laugh:)
But here's where it get's foggy, but I sure do remember that Rory had at least 4 "stacks" or maybe 5, of tweed amps.
I can't for the life of me remember if he had 3 tweed twins on top of 4, 2x12 tweed bottoms sitting up right or 4 tweed bassmans sitting on top of 5, 2x12 tweed cabs? I do remember the stacks were all the same height, they looked well road worn and had torn grill cloth.
Almost ALL the lead players that I remember back then had their amps "stage left" so from the seats to our right, as did Rory, next to the drummers hi-hat/snare, which was opposite of almost all the bands before. They always had the bass player right next to the drummer's hi-hat/snare for eye contact. It was and is still sound logic in my mind, but the rock thing had a different driver relationship between the drummer and himself than the older styles of American music. rock guys want to drive the music and the older forms "floated on top of the bass/drums and didn't drive it, they road it like a surfer on top of a wave. (Hey JJ you out there buddy?)
There's no way to know at this point IF Rory used 2 5G4's or 1 GZ34 in his 55 bassmen but I will be looking for if I can SEE on any DVD's I have IF the tweed aps on them have a mid control!
All in all I think you sir found a real gem, which has already been proven even if Rory didn't play one!
Brad :m8
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Man you got a great memory! I cant find my wire cutters even when there right in front of me. Rory Gallagher was incredible! A friend of mine has a friend who owns a music store in Chicago. He told me to pull one of the 5U4 rectifiers. My GOD man this amp was really ment to use a single rectifier for guitar. With both rectifiers it is tight and strong. With one it comes alive with insane sweet bluesy warm charm and sustain i did not think possible from a cathodyne PI. I am so used to the LTPI with it's much higher gain factor and have never used a 12AY7 preamp before. The gain i am getting from this amps PI is more than beautiful. Smooth,warm,crazy and more controlled. Not hashy or anything like that. I love it!