Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: pbman1953 on May 12, 2017, 07:31:01 pm
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After talking with Ed, I want to possibly increase filter values for my Traynor.
It's running out of power compared to my Fender 300T. I know, and Ed has explained that the Traynor is not a 300 watt amp. But I've run my Fender with 4 -6550's compared to 6 and still it kicks but as far as sustain and attack.
The Fender does have 3-330uf's / 450 volt. In my amp now I have a 100uf going in series like the schematic into an F&T multi cap 40 +40/ 450v. I've seen a F&T Multi with 100 + 100. My question is why is the single 100 in series (with the 40+40) and not parallel with the others to get a higher total? This design is done twice side by side in the schematic
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Power output is determined by the B+ voltage, the power tubes used, and the output impedance and how well that matches what the tubes want to see. So breaking that down further, your power supply which includes the power transformer, the filter caps, type of diodes (tube or solid state). Four 6550's will put out more power on the same voltage than four EL34's any day of the week, so you are comparing apples to oranges. Going with larger caps in the power supply will allow that amp to reproduce bass frequencies quicker, so the bass will sound tighter and a bit more present, but it won't give you any more power out of the amp. Use more efficient speakers or more speakers if you want more volume.
Traynor did their filtering in a strange way with one 80uf 450v cap in series with two 40uf 450v caps in several places in the amp. For identical caps in series ,the caps halve in value but double in voltage. Caps in parallel with identical values double in value and stay at the same voltage. So what they end up with there is essentially a 40uF 900 V cap, which I assuming they did because they wanted a higher voltage capability at that node, but they could have done it cheaper than they did. ((Two 40uF 450v in parallel = one 80uF 450v cap; one 80uF 450v cap in series with one 80uF 450V (two 40uF 450V in parallel)= one 40uF 900V cap)
Anyway, in summary, getting more power means a higher B+ voltage aka a different power transformer, changing the output transformer to one with a different impedance that matches the power tubes better (possible but not likely since the manufacturers usually designed for the proper load for max power), changing to an output transformer that is designed better with better frequency response and better metals used in its construction, (unlikely since Traynor used Hammond transformers which are excellent quality), or redesigning to use larger power tubes that put out more power such as the 6550/KT88. As you can see all of these approaches cost a lot and are a lot of trouble. It would be easier to sell it and buy a bigger amp, but you already have those....so just enjoy the tone you are getting and live with the lesser power.
Greg
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Greg
This amp has 4-kt120 tubes running and a new Heyboer amp that is set up for 4 or 8 ohm operation.
So having higher capacitance, say 250uf at 450volt is not better than 40uf at 900volt. In my car audio days we loaded a high-end system with one 1farad cap at 20 volts dc. The systems total benefited and the bass was so much cleaner and tighter.
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My question is why is the single 100 in series (with the 40+40) and not parallel with the others to get a higher total?
Your B+ voltage is 540V but the filter caps are only rated for 450V. So the caps are put in series to increase the voltage rating so they can operate with 540V applied. With this series arrangement each cap will only see 270V.
You can increase the cap value as much as you want but you will have to increase the value of all three caps. For example, right now using the 80µF and 2x40µF can gives a total of 40µF for the first filter. To increase to 50µF total you would need a 100µF and 2x50µF can.
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I should of mentioned that I do have one 100 and a 50 + 50 multi per section, all rated at 500.
I've found a F&T multi with 100 + 100 at 500v plus a JJ
250 at 500v
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> running out of power compared to my Fender 300T
The Fender 300 is beyond any other guitar-amp. Perhaps inspired by the SVT but significantly more robust. What other amp uses a 6V6 as driver??
>> I do have ..., all rated at 500.
> Your B+ voltage is 540V
500V caps will work at 540V, for minutes or maybe days. Then they BLOW UP. Sure to die at a bad time.
You want to stack 350V caps to about a "700V" nominal rating.
That multi-multi-section scheme was just cheap in the day. It is NOT a good design.
Today we would use "snap caps". Yes, BUY caps; you can't beef-up an amp this large with spare parts. Drill some insulating board (Doug sells it) and stick the caps in, connect the legs.
(http://www.tubelab.com/images/AssemblyManualSimpleP-P/C_top/C1_caps.jpg)
40uFd (80u + 40u||40u) total on an amp of this Voltage versus Current is just Pete being commercially cheap. From a clean sheet, I would aim for 100uFd to 400uFd. 470uFd 350V is a standard size single cap. Two stacked is 235uFd (6X more than stock) with ample voltage (blow-up) rating. You need another such pair for screen grids. Four 100K 2W resistors to bleed/equalize. Your 500V caps can go at the C29 C32 positions. (They run at 355V or less, but at turn-on they rise toward 500V.)
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Or if you rather work with axial caps you can get four 220µF @ 350V for $20.
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I like that design and I took out the old can caps . I'll have to put 2 on top and 2 inside.
On C 29 & 32, I have 2- 100's at 450 volt, is it worth it?
I have a 80 /500 on 29 and a 10/500 on 32, now
Also, If I use the 50+50 (I have now) as a 100 for c29, would it matter if the 100K resistor is still across it, or should I remove it?
Thanks
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On C 29 & 32, I have 2- 100's at 450 volt, is it worth it?
Not likely to help with the "running out of power compared to my Fender 300T" issue. Increasing the size of C26, C27, C28, and C30 should stiffen up the power amp a lot.
Running KT120s is not gonna boost the power unless you put a bigger PT in it also.
Just for general knowledge... When you connect two caps in series the total capacitance will ALWAYS be less than the value of the smaller cap. The formula for total capacitance is the reciprocal of the sum of the reciprocals.
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Interesting you say stiffen, in the car audio world the big 1 farad caps are call stiffening caps.
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> in the car audio world the big 1 farad caps are call stiffening caps.
Which would be used with amps of somewhat more power than the YBA. But let's go with this.
The supply voltage ratio, 540V to 12V, is 45:1.
For the same power, the YBA's current must be about 1/45 of the car-amp's current.
45X45= 2,000.
If a 1F cap is good for the 12V car-amp, a 1/2,000F or 500uFd cap would be good for the 540V YBA3.
Actually the 1F cap is used with more-Watts amps than a YBA3. (YBA ~~ 180 W, big car amp >1,000W.) That's why we are steering somewhat lower than 500uFd. Say "about 200-300uFd".
The cap MUST stand 540V (plus safety margin). Electrolytic caps go to 450V, sometimes 500V. The oxide can't be made thicker. So we need to stack caps. Two caps series is twice the voltage and half the uFd. So we need at-least 270V caps (300V is marginal, use 350V) of about 400-600uFd each. 470uFd 350V is a common size. Makes 235uFd at nominal 700V.
I do not know why the screen-node caps are as large as the main caps. I suspect they could be less than half the size of the mains. 100uFd-150uFd. The voltage stress is about the same, 535V. So pencil two more 350V caps but at 200ufd-300uFd each. 220uFd 350V is a common size. Makes 110uFd 700V.
Or since caps are cheaper by the dozen, six 220uFd 350V or a full 10-pack of 150uFd 350V. Use six series/parallel for 225u 700V, four series/parallel for 150uFd 700V.
I once upgraded several Bogen 300W amps with bunches of caps, about like this. Made a difference. Just 360W but much smoother at full roar.
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https://www.parts-express.com/resources-stiffening-capacitors-faqs (https://www.parts-express.com/resources-stiffening-capacitors-faqs)
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That's them. I had 2 caps in my car . They made a huge difference as far as attack and sustain.
In the mid 90's I bought the 1 Farad caps from Sprague and sold them to Car Audio companies like Parts Express and Amp maker Phoenix Gold. Sales were hot because it was new and highly recommended by the gurus of car audio at that time Richard Clarke. Rochard's Grand Nation is a story alone iof itself. One of a kind and here's the article about his car.
http://www.mobilesoundscience.com/showthread.php/447-Richard-Clark-1986-Grand-National-1992-CA-amp-E (http://www.mobilesoundscience.com/showthread.php/447-Richard-Clark-1986-Grand-National-1992-CA-amp-E)
My only competition was a company called Lighting Audio. He bought his from Phillips. Sprague was considered the gold standard as far as the big caps. Lighting convinced Philips to change the traditional outside wrap to show graphics of the the company that bought them. Sprague was very hard nosed not to do that because they felt that the wrap could not be played with because of its job to contain it in the event of a a blow up. Lighting seized that opportunity and was so successful that Sprague sales decreased. By that time thre amp maker made thier own deals with overseas vendors. I moved and lightning sold to Rockford Fosgate.
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Sorry to be a paid about this question, possibly it was overlooked.
Also, If I use the 50+50 (I have now) as a 100 for c29, would it matter if the 100K resistor is still across it, or should I remove it?
The schematic doesn't have a resistor across it.
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I would wire it like the schematic.
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Ok, thanks, back to work I am.
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Any suggestions where to get the caps?
I'd prefer one with the ringed terminal instead of a straight terminal
Thanks
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Click the capacitor link at the bottom of this page.
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I did but I didn't see the style and value size I want,
Antique doesn't have it . Weber is too difficult to look up. Mouser is also hard to look up unless you know every bitty detail.
The 470uf/350 doesn't seem to be as common. Plus inside I can't go too long. The 2" height works and I have to put the side ways. Outside I'm fine with most heights. The old can caps were 2 1/2" high.
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I doubt you will find a 470µF/350V cap at any of the guitar tube amp suppliers. IMO 470µF is excessive for any tube amp. 220µF is common and all the suppliers you named have those.
Mouser has several 470µF/350vdc caps to choose from. You don't need to know "every bitty detail". All you need is the value and voltage rating. Learn how to use their filters. It's really easy. Ignore the filters if you don't know what they mean but you must use the value and voltage rating unless you want to scroll through hundreds of pages of caps. It took me about 2 minutes to find several 'snap-in' style 470µF/350V caps.
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another source.
http://www.arselectronics.com/ARSWEB/CapPage2.html (http://www.arselectronics.com/ARSWEB/CapPage2.html)
--pete
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http://www.mouser.com/ProductDetail/Nichicon/LGN2V471MELC30/?qs=sGAEpiMZZMvwFf0viD3Y3RXRUVU1xXQD5rn7hNYrnMY%3d (http://www.mouser.com/ProductDetail/Nichicon/LGN2V471MELC30/?qs=sGAEpiMZZMvwFf0viD3Y3RXRUVU1xXQD5rn7hNYrnMY%3d)
http://www.mouser.com/ProductDetail/Nichicon/LNT2V471MSEC/?qs=sGAEpiMZZMvwFf0viD3Y3RXRUVU1xXQDO31KBdyuATk%3d (http://www.mouser.com/ProductDetail/Nichicon/LNT2V471MSEC/?qs=sGAEpiMZZMvwFf0viD3Y3RXRUVU1xXQDO31KBdyuATk%3d)
--pete
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cap clamps for the 35mm dia parts.
http://www.mouser.com/ds/2/88/hardware-20153.pdf (http://www.mouser.com/ds/2/88/hardware-20153.pdf)
http://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/TH25/?qs=sGAEpiMZZMsYDbxkXDKK1omjIvfDQx%252b%2fkzIXVTnNKFs%3d (http://www.mouser.com/ProductDetail/Cornell-Dubilier-CDE/TH25/?qs=sGAEpiMZZMsYDbxkXDKK1omjIvfDQx%252b%2fkzIXVTnNKFs%3d)
--pete
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Neither of those Nichicons are in stock, but several others are.
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http://www.mouser.com/ProductDetail/United-Chemi-Con/EKMQ351VSN471MA30S/?qs=sGAEpiMZZMvwFf0viD3Y3Wd4FpOoUsJZj2DkBmbVyFM%3d (http://www.mouser.com/ProductDetail/United-Chemi-Con/EKMQ351VSN471MA30S/?qs=sGAEpiMZZMvwFf0viD3Y3Wd4FpOoUsJZj2DkBmbVyFM%3d)
copied wrong window.
the screw term cans are due in next month.
--pete
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if it were mine: for c26, c27a+b, c30, c28a+b id use 4 of the parts in this link (https://www.amplifiedparts.com/products/capacitor-jj-electronics-385v-350-f-electrolytic)
for C29 one of these in this link (https://www.amplifiedparts.com/products/capacitor-jj-electronics-500v-5050-f-electrolytic).
with 3 of the horizontal cap mounts from the mouser link above - the TH-25 clamp for horizontal mounting 1.375" dia. parts c26, c30, c29.
--pete
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"if it were mine: for c26, c27a+b, c30, c28a+b id use 4 of the parts in this link (https://www.amplifiedparts.com/products/capacitor-jj-electronics-385v-350-f-electrolytic) "
I don't think I have room for that. As is I had to remove the 2 topside can caps. I'm figuring 2 outside and 2 inside.
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"if it were mine: for c26, c27a+b, c30, c28a+b id use 4 of the parts in this link (https://www.amplifiedparts.com/products/capacitor-jj-electronics-385v-350-f-electrolytic) "
I don't think I have room for that. As is I had to remove the 2 topside can caps. I'm figuring 2 outside and 2 inside.
looking at some chassis pics posted by others looks like they will. measure.
--pete
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Ah yes, never quite satisfied. I know the feeling well. Went to 2 shows this weekend. 90's Country/Rock is the best way to describe. Little Texas and Sawyer Brown. Both did a great job, but I have a preference. Little Texas hit the stage with no backline, just instruments and drums. They did a great show and everyone at the place was having a good time. Music sounded very much like the recordings as things seems to be today.
Sawyer Brown, different story. Little older gents, few more hit songs and more stagehands. Full backline with a Fender Twin, Ampeg SVT, a Blue one with 8, 10's, Lead Player Metro Plexi 4 holes 100 watts and drums behind Plexiglass.
My point, not a damn thing. :l2:
Seriously, Sawyer Brown sounded live and alive. Not to take away from anyone as we all are playing the way we are required today and I have even looked at a couple of things like the Headrush pedalboard and the molding or profiling like the Kemper.
Yes, I hear it too and it is a problem for me so I do as you. Keep tweaking what was perfect last week. I happen to own a 72 SVT and I will say it is one fine sounding amp, but it does not have the sheer girth of the Fender 300 and in the tube world it is rare. They call it a 300, but it is more than that.
The Traynor amps are fun to have around and you can do about anything you want to with them. The basis is great and one of the few handwired amps that have not skyrocketed, these and a few Laney's, but even theses are getting expensive.
Give it a try on upping the main filters. You will notice a difference. Just like all the things you have done to the amp, all of it has made a little difference and all the little differences obviously you are liking.
Just keep in mind your voltages and have fun. There is always a way to add more. Can you say Big Doghouse. :icon_biggrin:
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Just to report back that I've ordered-
4- JJ- 550UF @ 385 Volt
4- 220K- 3 watt- resistors
I'm pretty psyched to get this done.
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Forgot to ask If after the install if I have to rebias?
Thanks
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Forgot to ask
If it were me, I'd recheck all my power rail taps and bias, just because I changed things
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I'm not sure what happened but it's blowing fuses. I tried to be very careful.
No smells , no noise. It was instant. The Light came on them off.
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Does the fuse blow the instant you flip the switch? It's possible you wired everything correctly but the inrush current filling up all that capacitance is too much. If it's a fast-blow fuse then you can try slow blow. Or add a NTC thermistor, either in the secondary or the primary leads of the PT.
Or put a big power resistor in series with the ground leg of the rectifier with a switch that shorts the resistor. You power up the amp with the switch open letting the resistor limit current then flip the switch after a few seconds. Maybe 1kohm @ 10 watts? Just guessing what might work.
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To be sure I flip the amp and vacuumed it. I tried other fuse but under value to be safe. I disconnected the new stuff and still they blew. I'm out of value fuses. All I have are ceramic 10 amps. I tried a 7 amp clear with metal center and it blew. I'll have to get more 5 amp tomorrow.
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Maybe you have a wiring error? Maybe that amp doesn't like 550µF caps?
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Post photos of how you have it wired. Put it on a bulb limiter, 100 watt at least. It should hold a 5 amp fuse, so you have an issue.
I want to see each cap, where it is connected and what it connects to. I believe you may have grouded your series caps. I say this because you are not mentionong a blown cap.
Do not put another fuse in and power up. Photos from diodes to caps.
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ED
I'm not sure what you mean about the bulb limited.
Here are the pics but I'll have to repost due to the amount of pictures
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next batch
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Would it be possible, and without harm, to remove all the those caps, off the connections , just to see if the lights turn back on?
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Much easier to just disconnect that green cloth covered wire from those green diodes. Then compare the schematic to your actual wiring to determine the wiring error.
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Hmm, I removed the wire at the diodes and it still blew.
Possibly my PT?
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Possibly, but I'd first suspect shorted diodes. Disconnect the two red PT wires from the green diodes. Fuse hold now?
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You nailed it!
Lights and fan only
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So, you need to replace all 6 of the diodes. But even more important... Find the wiring error that killed the diodes. Your pics are good quality but we really need to see pics that show how all of your new filter caps are connected together, ie, show all caps in one pic so we can trace wiring.
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I was lucky and just got back from an electrical house that had NTE 1N4007 diiodes-
1 Amp @1000 volts
I install all new 7, even the bias location. I figured why not.
I turned the amp on, minus the green wire cap feed, and all's good.
2 out if the 7 diodes were bad.
Here are more pictures
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Is it possible the that diodes failed because they couldn't handle the new parts?
For the most part I think the wiring is correct.
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Is it possible the that diodes failed because they couldn't handle the new parts?
Yes. Those huge filter caps you are using will demand a huge initial charging current through the diodes. And if that is the case, your 1N4007s are at risk of the same failure. Those green bullet diodes are rated at 1A just like the 1N4007s. I would replace those 1N4007s with 1N5408s that are rated 1000v/3A. Less than 40 cents each.
It's also possible that the huge initial charging current will strain the PT to the point that it fails.
So, plug it in and measure the B+ voltage. What have you?
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I could of gone with the 3a but I wasn't sure if they were overkill or not. I can get those too. Hopefully for now the 1A will get me by. The guys at the store said that ones he gave me were 1 Amp but at 1000v. The PH204's in the amp were 600V
On the B+ , I wasn't sure if you wanted AC or DC, so I measured both
DC- 710
AC-293
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DC-710! That's considerably higher than the 540V shown on the schematic. Did you have the power tubes plugged in? Where did you measure AC-293?
Does the amp now sound like you wanted it to sound? Not running out of power?
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Keep in mind that I did the measurements with the cap feed-green wire off. I took both measurements from that point.
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Well then, those voltage readings don't mean very much. Guess you don't know how it sounds yet. Keep us posted.
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Since you to told me to disconnect the cap feed, I was afraid of reconnecting until told to.
I can give it a go .
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> wasn't sure if they were overkill
"No such thing" as overkill when specifying an amp this big.
The normal PIV for the apparent 400V AC and some assumptions is 1,130V. Three 1,000V diodes series is just enough overkill.
The startup first-cycle current is 24 Amps!! Once started, 3.3A peak and 0.83A RMS. The 1A diodes are right near the edge of death.
> 1N5408s that are rated 1000v/3A. Less than 40 cents each.
Agreed. Buy six; you need at least two-series in each leg to stand the PIV, and I've learned to use more-than-double PIV to survive line spikes. 1,130*2= 2,260V needed, so three 1,000V parts each leg.
I would not worry about PT damage. It takes time to heat large copper. The peak current comes way down real quick, pretty OK by the second cycle.
Ah-- the real danger to PT is when marginal diodes short-out. "Overkilling" from 30-cent to 40-cent (or even $10 retail) diodes may save a $200 PT from smoke-death.
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PRR
In that case , should I not try it with the diodes I have installed?
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I am not PRR, but I would try it. You might lose a Diode, but I doubt it. It would probably take a while to kill them.
You need to build a light Bulb current limiter. You can search the forum, do a Google search or best of all, search for a link to Sluckey amp scrapbook. It has instructions to make one and other things you should read.
Did you do anything that could have killed the diodes like hooking up wrong initially? We need to find the cause of the Diode failure. Could be over stressed.
Easy to make a mistake with diodes and they pop easily if current hits them the wrong way.
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I am concerned you may be getting confused with the series caps.
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Ok, partial success.
I turn amp on , no fuses blowing.
I threw the stand by and there's a hum , low volume and one tube red plating.
I know that's not good.
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I cannot see for sure, it looks as if you have from the diodes a green wire that is your B+ and it probably goes to a switch. From the switch you have a blue wire then a resistor then a red wire and a resistor then a black wire going to ground. If this is correct you have grounded your B+.
From the first series cap, which appears to be the one with the red wire on the negative side of the cap. From the positive side of this cap is where your next B+ connection is made. Yes it will still be grounded, but your current will have somewhere to go.
If this is how you have it, do not power up the amp.
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You have something miswired. Check and insure my previous post.
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I am betting that you have no connection from your first series caps to the screen node.
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The green wire is the cap feed-
Also attaches to-
15k/5x(r31), input to the Classic Tone chock (r42) & Blue wire to new C27 A&B
The return from the Classic tone goes to the C28 A&B & the 1k 25w (R30)
The blue wire off the standby is the new filament transformer (green)
The red wire off the switch is really the red/yellow from the PT
The resistors you see were a mode, I think you suggested and then not to use the PT- green / yellow wire.
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Do you have a variac? Any way to reduce your ac voltage. I do not know if you pull your tubes if your unloaded voltages will kill the caps.
Anyway, what I am getting at is being able to check voltages. Sit tight and maybe one of the guys who knows for sure will let us both know. I do not want you to kill the new caps.
Checking volts will let us know, but red plating is a sign. Anyway I can assure you it is not wired right and I can't see for sure because of the wire splicing. I cannot follow the path.
Build a bulb limiter ASAP!
I am still looking at the photos, but I am not sure.
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I can't tell how it's wired from the photos either.
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Rich the wire going to the 550 350 caps is yellow and spliced, correct.?
If so, where it connects you should have a wire from it connected to the next node. Where does it connect? It looks like it just goes through the caps to ground. It needs to connect to the next node.
Tell us where this wire continues to?
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That yellow wire is only extended to reach the caps.
It goes from the 550's to the 1K25W res & other side of r42 (classic tone choke)
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I tried a test to see if that plating tube was bad so I moved it to a different socket.
The same socket glowed so I guess the tube is ok.
Still with the same issue
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pull all the power tubes. measure dc voltage at pin 5 on all 4 power tube sockets. make sure they all read the same. use a octal socket base on the suspect socket to make sure the socket pins are making contact with the tube base pins.
octal base - https://www.tubedepot.com/products/8-pin-octal-tube-base-only (https://www.tubedepot.com/products/8-pin-octal-tube-base-only)
--pete
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Good point.
I can do all this later and report back. I'll check the #5 and then I'll flip the amp over and see if all the pin sleeves are in a correct position. Possibly tighten them too.
Thanks
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Will you be playing bass through this amp?
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Yes, only bass.
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Measurments-
From diodes/ C27 A&B- 575 volts
C28 A&B- 574
tube 1- term#5- -102 in stand by, -064 On
Tube 2(red plater) - +70 in stand by, + 274, when on
Tube 3 & 4 - similar to tube #1
C29- +092 in SB, +370 when on
C32- +139 in SB, +283 when on
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Tube 2(red plater) - +70 in stand by, + 274, when on
Gotta fix this.
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Sorry to say but have to be honest, that I had the #5 pin, on the plating tube, hooked to the preamp feed line.Same as C32, Hence getting 274 volts. I found the right connection at where the line comes from the bias pot.
no hum, super quiet. No time now to button up. Will have to clean up a little, re bias and get the 3 amp diodes.
You guys are the best , thanks.
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If I have a 3.3 k for R51 & 52 do I need r26 & 27?
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probably not as long as you wire it correctly. I personally like to solder the grid R's right at the socket so I would probably use 4.
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R51 & 52 are on the board
26 & 27 were wired at the #5 pin
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If I have a 3.3 k for R51 & 52 do I need r26 & 27?
Yes. You need all 4 of those resistors.
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if it were mine, i'd change R51 R52 R27 R26 to 10K 1/2watt carbon comp. resistors and locate them at the socket if possible.
--pete
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Hmm if thats the case try to following me here. Please go to reply 45 and look at the middle picture.
Keep in mind that Ed suggested a while back to change R24 & 25 to 100 k and R's 51 & 52 to 3.3k.
There are 4 -#5 pin wires.
Tubes starting from the left:
The #5 wire is direct to the board - w/ 3.3k to 100K then to bias feed- This is how the amp came with no 1.5k attached
Second tube- From pin 5 with a 1.5K shrink under the wire- Black shrink to Green cloth, to r25 & 51 joint
Third- from pin 5 with a 1.5K shrink under the wire- Black shrink to red cloth to R 52 & 24 joint
Fourth- From pin 5, green cloth wire to r52 & 27 joint with no 1.5k resistor.
The point I 'm trying to make is the out side tubes do not have the 1.5k resistor and insides do.
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The point I 'm trying to make is the out side tubes do not have the 1.5k resistor and insides do.
The point I'm trying to make is... wire it like the schematic. Those Traynor folks were probably a lot more savy than me.
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Ok, I'll do that.
Thanks
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Did the amp ever work?
If so, why are you adding/subtracting/changing resistors?
I thought the project was Big Caps. Don't complicate it by changing other things until the ONE big change is proved.
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Yes it did work. All I wanted was a cap upgrade. But I noticed parts that were missing compared to the schematic.
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Here's what I have found as far as connections compared to the schematic. Please keep in mind when I originally started to update parts with what I saw and replaced part for part. Now, with the help of the forum I've learned to use the schematic more.
So that being said I've noticed a weird thing.
C18- is connected at the joint of R25 & 51 , the other side goes to lower connection (on schematic) of R23
C19- is connected at the joint of R24 & 52 , the other side goes to upper connection (on schematic) of R22
Since the routing was not the same as on paper , what's the effect?
Thanks
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C18- is connected at the joint of R25 & 51 , the other side goes to lower connection (on schematic) of R23
C19- is connected at the joint of R24 & 52 , the other side goes to upper connection (on schematic) of R22
Again, that's not right. Make it like the schematic!
What's the effect? V4 and V6 have no grid stoppers. V5 and V6 have two grid stoppers 1.5K + 1.5K = 3K.
Wire it according to the schematic.
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ok, I'll do that. Again, I've made some errors but won't take credit for this one. :worthy1:
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Hmm if thats the case try to following me here. Please go to reply 45 and look at the middle picture.
Keep in mind that Ed suggested a while back to change R24 & 25 to 100 k and R's 51 & 52 to 3.3k.
There are 4 -#5 pin wires.
Tubes starting from the left:
The #5 wire is direct to the board - w/ 3.3k to 100K then to bias feed- This is how the amp came with no 1.5k attached
Second tube- From pin 5 with a 1.5K shrink under the wire- Black shrink to Green cloth, to r25 & 51 joint
Third- from pin 5 with a 1.5K shrink under the wire- Black shrink to red cloth to R 52 & 24 joint
Fourth- From pin 5, green cloth wire to r52 & 27 joint with no 1.5k resistor.
The point I 'm trying to make is the out side tubes do not have the 1.5k resistor and insides do.
Little explanation as to the resistor changes.
Referring to the change in grid leak size when using the KT120 tubes reducing the grid leak is a balancing act. The grid is in relatively close proximity to the (heated) cathode, therefore the grid has a tendency to warm up a bit itself, and can emit a few electrons. This would otherwise cause the grid to become charged, were it not for the grid leak, which allows these electrons to be replenished from the ground return, thus keeping the grid at the desired grid-to-cathode voltage. More powerful tubes have a higher propensity for the grid to warm up, so you want a smaller grid leak resistance (all other things being equal) to ensure the grid remains at its desired potential.
The recommended change of those resistors is a result of me burning up a quad in 2 Dyanco amps. The 100K was recommended from New Sensor for *most* circuits. I had a super lead Marshall running them with 150K grid leaks and even had to reduce these some. His first set of tubes got very noisy and he has to replace them.
Also a couple of changes in V1 were done to add more warmth and the 3.3K replacing the 1.5K seems to smooth out the attack some in a Bass amp. At least it does to me.
I write this so you guys who are helping him know why the resistors were changed. None of these things should have been done while the change in cap values and the amp was running fine, however I did not know 2 sockets were missing grid stoppers.
Please correct anything I may have steered Rich wrongly with. This does not include lead dress. I had nothing to do with this. :icon_biggrin:
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C18- is connected at the joint of R25 & 51 , the other side goes to lower connection (on schematic) of R23
C19- is connected at the joint of R24 & 52 , the other side goes to upper connection (on schematic) of R22
Again, that's not right. Make it like the schematic!
What's the effect? V4 and V6 have no grid stoppers. V5 and V6 have two grid stoppers 1.5K + 1.5K = 3K.
Wire it according to the schematic.
Also, what's the adverse effect of the caps (18 &19 ) not wired right?
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Also, what's the adverse effect of the caps (18 &19 ) not wired right?
Modify message
That depends on ***HOW*** they are miswired. I looked closely at your hi-rez pic of the board in that area and I saw several bad mistakes. I bet if I had my hands on the amp I could find more. Someone with poor soldering skills has been all over that area of the board. I suspect their electronics skills match their soldering skills.
It's not important to know who boogered this amp but it's up to you to make it right. I've been harping "make it like the schematic". I don't know that we can untangle it for you over the net. If you can't make it like the schematic you should take it to someone who can.
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Sadly , I know it's not very pretty so I'll see what I can do to try and do some house cleaning.
Totally appreciate you and all the members for getting me on the right track.
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I'm in much better shape. I got the parts to make sure all pin 5's had 1.5k resistors.
I did have a casualty in that red plated tube may be dead. It measures half the ma current compared to the others and all 4 sockets have the same measurements at their pins.
I moved the bad tube around and the issue moved with the tube.
Looks like I need one tube.
Also from a quick test out the amp is stlil very quiet and punchy.
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Often when you have a tube red plating, and you are working on the amp and trying to troubleshoot without fixing the issue causing the red plating immediately, then that tube will be irreversibly damaged. The bias on that tube will be way off from the others and it won't have a stable bias and will drift and eventually red plate again. Sometimes the other one in the pair can also be damaged. Red plating is something you want as little of as possible, and you want to fix as soon as possible, preferably without running the tubes in circuit while you are troubleshooting. You also should make sure the socket didn't arc as it will make any tube put into that socket malfunction if the socket has arced.
Greg
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Thanks Greg.
I played the amp tonight and sounded real good. Even with one bad tube. I ordered a new one. I'll write back after I get it.
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Just a further update on the amp and it's doing well!
I was talking to Ed about tweaking some of the characteristics to the sound and he told me to install 4 - 3.9k resistors to all 4 pin 5's . I do have 4- 4.7k and I'm wondering if that's too high a value. Otherwise I'll have to get the closest I can to 3.9k. Most likely the store will have 4k.
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3.9k is a standard value.
--pete
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Thanks for that, Pete, but to save a trip , is the 4.7 too high a value for that usage?
I've seen some Marshall, which Ed said the amp is based on, with 5...k
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they'll work. marshall uses 10k in that position.
--pete
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I tried the 4.7's and there was an improvement. Thanks