Peavey Vintage chassis questions

[Shack]

I have aquired this chassis complete with the 6C10 tubes and everything but power tubes. I have plugged it in with current limiter and without, and all looks well....since I dont have 4 6L6, I put one in each pair and plugged a speaker in.....power tubes didnt appear to light up, but the amp had some serious hum , and the pots appeared to affect it. The electrolytics are all original id say.

My questions are....

1. Can I use these monster trannies for a 50 watt amp, since I dont desire the amp restored?

2. Whats the best way for me to test all the secondary leads to mark them if I can?

3. It is ok to use 2 tubes if plugged in properly on a 100 watt amp, right?

4. Is there a legible schematic to this amp?

5 Are the compactron tubes good to use for a project? their filaments lit up well and they appear to be good.



Thanx, thats it for now?

[shooter]

#4 is where I'd burn most energy now.
that helps everyone with most the other ?'s

I'm doing a re-draw of a 100w to 50w, best I can see for quick dirty; double speaker impedance, re-bias, expect to tweak B+ and screen taps, test and adjust.

[sluckey]

Call Peavey.

[eleventeen]

You can certainly get a schematic. My 5 minutes of effort did not fetch one, though.


Some higher-power Peaveys have separate fuses for the heater filaments. I bot a dead Peavey MX head, the one in the road case cabinet, for $50 last year with 4 really good 6L6's in it. It had an open heater fuse for the 4 x 6L6 so it cost 25 cents to fix.


What do you want to do with the amp? Just make it work as is but with 2 output tubes?

[Shack]

Yes, I want to use it as a 50 watt amp, would like to use the nice iron here.

I found a schematic, but its hard to read

[eleventeen]

So, you should be able to run it with only two 6L6, but those 6L6 have to be on opposite sides of the PI. The best way to guarantee this is to install the 6L6 in the outermost sockets. Eg; 1, x, x, 4. Either way you count.


You say the ecaps appear original. This is a circa 1975 amp, so you do the math.


To clarify, you have (only) the bare chassis? eg; no reverb can?


If even without any output tubes plugged in your lamp limiter did not glow bright, then maybe those caps have some life left. But probably not much.


Are you skilled and equipped with a meter and able to troubleshoot beyond flipping tubes?


IF you have a meter, strongly reco you measure bias to the output tubes...should be in the area of negative 50 volts on pin 5, all of them.


If you DON'T have a meter............................................Stop!


The compactrons are potentially irritating to replace because of their cost.


In general I would seriously doubt you have a transformer problem, but the primary (6L6 side) can be tested for continuity.
There are two pairs of 6L6. Most likely (regardless of how you count, left to right) you'll have almost no resistance between pin 3 of 6L6 #1 and 6L6 #2......and zero resistance 6L6 #3 and 6L6 #4. Between 6L6 #2 and 6L6 #3 you're likely to find 250-300 ohms.

There is NO GREAT COMPULSION to make this continuity measurement but if you decide to do so, MAKE SURE the amp has been turned off for a minute or two before you do so. You DO have the fabled balancing resistors which also act as bleeders, assuming they are good and not blown nor burnt open, but they will take 1 minute+  to discharge the power supply ecaps. After that minute goes by, measure DC volts on the plates before you measure ohms. The closer to zero, the better.
 

[Shack]

I have a meter and I know the caps are old. Im concerned that without a load there is 512volts on the plates, and not sure if my 6L6 will handle it....they are weird, groove tube 5881/6l6wgc marked on them.

My lamp limiter looked great with it, thats why I tried it with the tubes...so I know the caps are old and maybe pots too.

I will measure the bias voltage tomorrow and report back.


Oh and yea, bare chassis.

I just want to know if the OT will work well with a duet of tubes as well as a quartet, and I know the PT is overkill, but man, would be cool to use. ill keep the 6c10 for later if they may come in handy :)

[PRR]

Unless it is one of Peavey's Worst, a PCB and ribbon puzzle, it's gotta be much quicker to find and fix what's broke than to rip-up and re-lay a whole amplifier.

The smear of a schematic hints at a fine amp.

I would never use a Compactron in a new build (unless it was a Compactron Challenge, a 5-tube radio in 2 bottles). If it's already wired, as in this case, I'd stick with it for the time being. But supply and quality of these fast-fad tubes is dubious, so when it eventually annoyed me I'd beat out the 12-hole and put in two 9-hole sockets. (Maybe a 9 and a 7-- there's some good deals in NOS single triodes.)

[Shack]

This would make a great AB763 or Bassman amp chassis lol.....all I would need is to cut out the vent holes, add a piece of metal with 12ax7 holes in it and rewire.....voila :P

[Shack]

Yes PRR, thats what stops me....thinking this amp can be saved.....its just that it could never be the cool amp like we love.....sigh

[PRR]

I think it "IS" a Bassman, plus reverb, and designed for 100W.

I can't read all the part values but they won't fall far from the Fender tree and can always be changed.

The triple-triode Compactrons are in fact several assortments of 12A_7 guts, packed 3 to a bottle instead of 2. They likely come off the dual-triode guts machines, just assembled in a larger bottle.

If you mean: it won't look like a Bassman, be creative. All Fender upholstery and most trim is readily available.

[Shack]

:) a bassman with reverb would be sweet.....ill call peavey and try to get a clearer schematic and parts list

[sluckey]

Better schematic attached. IMO this amp is a keeper and worth fixing as is.

PS... Would you post some big pics of the inside and outside of the chassis?

[Shack]

thank you Steve, was hoping to hear that

[sluckey]

Would you post some big pics of the inside and outside of the chassis?

[eleventeen]

A pix found in my search for the schemo:


http://www.tdpri.com/threads/peavey-vintage-4x10-amp.312795/

[PRR]

> A pix found

Hah! Hartley actually designed it to "BE!" a Fender Bassman, down to the tweed, except doubled-up power output and 3-triode bottles which were readily available in 1972 (who cares about a future?).

The circuit IS a Bassman, with a reverb tucked inside where the second input channel and mixer should be, and a few changed values which could easily be Fender-ized.

But then he used a PCB. Not as tangled-up as later over-packed Peaveys, but I'm not real hopeful about 1972 PCB stuff in a hot amp holding up to repairs or modifications. If the board is good and the copper wants to come off, you "could" (big work) take the board out, punch the holes for decent turrets, do the traces over with proper wire, and then mod to heart's content.

Pop-Rivets is so 1972 also.

[tubenit]

After seeing the chassis photo and knowing it's 1972 PCB, I'd gut it if it were mine and build a Bassman that is cathode biased with two 5881's & install a passive effects loop just prior to the LTPI.  I'd use a 270R or 300R 10w resistor with 100uf/100v cathode cap for the 5881's.  I'd probably use a PPIMV for master volume.


OR ....... You may just want to repair it and discover it's a fine amp as is.



With respect, Tubenit

[tubenit]

My understanding is Dumble used Peavy iron in some of his builds so I would think it's pretty reliable iron?


If you gut it,  I'd take numerous high resolution pictures of PT, OT wiring & bias circuit if you go fixed biased (prior to gutting it).

[Shack]

here they are Sluckey

[Shack]

and last two

[sluckey]

Nice build quality! I'd definitely try to fix it. No filaments should be easy to diagnose. Hopefully the PT is OK.

This is a unique amp and not many around. This is my first time hearing about the Vintage. If you fix it as is, you'll have an amp that not many people have. I'm gonna bet it will sound good (and loud!) also.

Or, you can cannibalize it and build another ho-hum clone. 

Guess you can tell which way I'm trying to push. Definitely worth the effort to fix. Then you get to hear it. At that point, if you don't like it, tear it down and build something else.

[Shack]

Im guessing that because the compacton filaments work and I heard sound with the 2 power tubes plugged in, that I just didnt see the filaments and the loud buzz is just alot of bad electrolytics

[tubenit]

Nice build quality! I'd definitely try to fix it.

I agree with that!  Thanks for sharing the photos. Looks like you have something very nice to work with.

with respect, Tubenit

[kagliostro]

I agree, it worth the effort to try to fix

I would like to see one photo where is possible to see the whole inside in one picture (if you can)

Franco

[super&plexi]

I got out of high school in 78 and those were somewhat popular around that time I had the one with 4 Power tubes (6L6 if I remember correctly) and transistors in preamp, tone stack, and Reverb I think. I seem to remember possibly 12a_7 as a probable phase inverter, although it could have been one of those weirdos. There was also an opposite model and I think that had 6 or so possibly 12ax7 type tubes And Solid State power amp. And pretty sure there was a complete rip off of the bassman, normal Fender style 6l6 and pre's. I know I saw one but I guess it could have been hand-built. I know that's the one I wanted because it sounded better than the one I had and the others that I have seen what I remember from mine was it sounded exactly like you would think it was a ton of preamp distortion if you wanted it but the clean was really nice. Reverb was Fender(y) and not half bad either what a great time for equipment, Fender blond/brown reverb tank ( original) $50. Brown Bandmaster3x10! $300!....My Pop walked in w/ familiar looking Brown beat up Les Paul case NSAID Merry Christmas to me about June or July. My first was1 of 40  first Les Paul's... But back to your amp I agree with getting it up and running In-Shape if you can and then seeing if you want to mod. I never see them around anymore and I'm sure  people are interested to hear how they   Mine never broke after tons of backyard jams and it worked when I traded it for whatever it is I created it for I can't remember

[Shack]

Well, im ready to try to fix it. I am gonna try to remove the PCB and mark all the wires so hopefully I can reinstall.....that way I can start by replacing ALL electrolytics in the amp, then ill go from there. I did plug a guitar in while powered up with 2 tubes in, and besides the horrendous noise , that seemed to get louder with turning up a tone stack pot ( controls were facing away from me and hard to read on face) which I believe to be bad ecaps......I did get guitar out of it, if I pushed down on the compactron tube, so maybe need to tension the socket connections.

Still not sure if it would be better to try to repurpose the amp as a tweed twin with SS rectification, but if it doesnt cost too much to change caps and see what it does , may help my troubleshooting skills.

If it dont work and I decide to add 12ax7s and a rebuild.......then I would have to figure out best way to make the power supply work with a clone ( Twin/Bassman....Marshall)

I posted this to keep the thread alive kinda, so Slucky dont yell at me because I started 13 threads about the same thing :)

[Shack]

Well, due to the poor chassis condition and no cabinet or reverb ...and the fact that everything is tough to work on with the pcb, I decided that its easier to just rebuild. I have a couple of power supply questions.

1. This power supply has no choke, but a diode /resistor in that spot between Plate and Screen nodes...what is the diode for and if I can find room for a choke there, should I use a 4H/90ma Fender choke, or a 3H/120ma Marshall choke ( I dont really understand the chokes very well)

2. B+ on this amp should be about 480 volts when loaded with 4 6L6....all of the amps I have looked at  ( Bassman, Twin....and Plexi/JCM800 , all have lower B+ voltages. Should I drop some with a zener to ground on the negative side of bridge rectifier to get closer to them?

3. Since I have no idea of OT primary impedence , should I let that influence a decision on tube types or number of tubes used?

4. I think ill stick with the 100uf series caps with balancing resistors in first filter position, and use three 20 or 50 uf caps for other nodes, there really isnt room in here for using cans like Marshalls.


I think thats it for now, thanks all

[PRR]

I think you should re-cap then flip it for the 50W of your dreams.

This IS a 100+Watt amp and I don't think it will be happy as anything less.

Rip-and-re-render is a lot of work and you may get halfway and lose interest.

[Shack]

Would be a good idea except it really wasnt worth the 100 I paid for it with just an old chassis. I wont get bored with it , it will just take time to afford the parts and take the time to get each section right, starting with the power supply. I can keep it a 100 watt amp with any of the designs I have in mind ....at least thats what I intend to do with it. I will figure it out, thanx again

[Shack]

OK, I decided what im gonna do. This is an educational project after all. Yes this amp is a 100 watt amp, sooo...I will use a Twin reverb power supply/ and wire the sockets that way ( the filter bank is very close to what this amp already has....sans choke)

I will use a bassman board and put screen resistors on sockets along with grid resistors, so EL-34 will be out of the question.

Has anyone here built an amp in sections...ie...power supply/ power section / inverter / preamp? ....testing as you go?


I think that I run into problems building everything to a layout and then wondering if I did something wrong to make it not work out of the gate.

Im sorry if my aspirations are a pain in the butt, but I want to learn the stuff that I dont understand yet and you guys are the best tool in my bag, since you all already understand what im missing.

[hardhead]

I understand you are in deep water on this project....the 6c10 vintage is simply one incredible amp,made in 2/12,4/10,6/10 formats they will make most 50 watt Marshall guys cry.As Steve observed that pcb is old school meaning ...durable. I'm 65 and have owned four of them in different flavors,On my first one I called Peavey one afternoon to ask about tubes....A guy answered...seemed to be familiar with the amp,answered all my questions,we shot the breeze a bit ,I asked his name in case I had more questions.....he said this is Hartley ,they can always find me ,call if you need anything else.Like calling Fender and getting Leo.

[Willabe]

On my first one I called Peavey one afternoon to ask about tubes....A guy answered...seemed to be familiar with the amp,answered all my questions,we shot the breeze a bit ,I asked his name in case I had more questions.....he said this is Hartley ,they can always find me ,call if you need anything else.Like calling Fender and getting Leo.

    Nice!

[Shack]

Very nice.....If I had more than just an old chassis, I would restore this thing....but it appears that this has been worked on before.....so, Im gonna keep the filter cap pcb and rework this. with a bassman board and using a twin reverb power supply schematic.....I will have a SS tweed twin with no cab lol.....without alot of money invested. Only thing is to convert the vent holes into 3 normal preamp tubes that my dumb azz can understand.....but Kudos Hartley, this thing is built very well

[Shack]

OK, got some parts in from Doug....need to order the filter caps and board....I plan to use either the Bassman board or a plexi board, a couple questions. What is the purpose of the diode on the filter bank board, should I make room for a choke or keep it as is.....and whats the best way to mount a bridge rectifier/ the square one ( bolt it it chassis and solder to the long leads or use terminal strips)

Just tryin to do it right