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Thread: Need help identifying this amp

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    Need help identifying this amp

    I just bought a amp which i bought doa for nearly nothing. anyway im trying to find the schematic for it. i went to scematic heaven and believe it to be the classic b schematic under the peavey section but that schematic shows 2 6l6c and the owners manual says 6l6gc dont know if theres much of a difference but the (g) means something.

    I believe it to be a 1974 50w combo. your help would be appreiciated
    below I included some photos to help





    Thx

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  2. #2
    Lifetime Member Enzo's Avatar
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    It is a Peavey "Classic" and would be the A series. There are four input jacks, two bright and two normal. That is the A series. A B series Classic has four jacks, but they are one each bright, normal, series, parallel. Not what you have.

    Your amp uses two 6L6 power tubes. The B series schematic at SChematic Heaven is not for your amp, but if you look, it does say 6L6GC for the power tubes, not 6L6C.

    ANY 6L6 currently on the market is perfectly fine for your amp.

    Historical note: the original 6L6 tube was a metal tube. You can find these here and there today. They are NOT suited to guitar amps and have much lower ratings than modern tubes. But that is plain 6L6. A long time ago they made the glass version of the tube and it was the 6L6G - G for glass. Later, improved versions came out, the 6L6GA, the 6L6GB, and finally the 6L6GC. Good luck finding a 6L6GA. You probably can find NOS 6L6GBs out there, but don;t waste your time and money on them for this amp. 6L6GCs are made today. You can also find things labelled 6L6GB on todays market, but they are really not "real" GBs, and they would work fine too.

    You want some letters? I think the Ruby Tube 6L6GCMSTR is a real nice solid tube that is happy in this amp. But the common SOvtek 6L6 family of tubes would be fine, or any one of a number of current brands.

    Customer service at Peavey will send the schematic upon request. But here it is.
    Attached Files Attached Files

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    Old Timer oc disorder's Avatar
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    I'm no Peavey historian but it looks like a early Peavey Classic with a makeover !
    http://www.peavey.com/assets/literat...ls/classic.pdf

    EDIT : just read Enzo's post and the above manual and attached picture
    is for the "B series Classic has four jacks, but they are one each bright, normal, series, parallel. Not what you have."

    Thats the user manual.. probably preceeded the VTX ones and after the Mace/Deuce ones.
    You are the best one to tell which schematic matches by checking the components
    against the drawing but I think you are right with the 74 model.

    Regarding the tube suffix this could open a can of worms although a pinned reference
    on this site that could be added to would be a good idea as it often comes up.

    I thought GC meant Glass Capsule but therer are variations on it .
    It appears originally it was a 6L6G went through some revisions and became the 6L6GC.
    In your case it depended who wrote the schematic and what 6L6 was around at that time.
    See these links for more confusion !

    6L6 STR - GC etc. What's the difference ?
    6L6 STR - GC etc. What's the difference ? [Archive] - Telecaster Guitar Forum
    Tube Designations
    Tube Information
    Valve Type Numbers
    UK Vintage Radio Repair and Restoration - Valve Type Numbers

    This excerp from Tremo (October 22nd, 2005, 04:26 PM) on the Tdpri site is excellent !

    The alphabet soup of prefixes and suffixes you find in current manufacture tubes are mostly for marketing hype purposes, and have little bearing on what it all meant back in the old days.

    All this applies to the large octal base tubes. When 6L6s and 6V6s first came out, they were in a metal envelope. When the first glass envelope versions were introduced, they had a G suffix applied (6V6G, 6L6G). These first glass versions used the large bulbous shouldered envelopes. Then they went to the smaller tubular straight sided glass bulb, a T suffix was added, hence the 6V6GT (glass, tubular). A later beefed up version came out, which was called the A revision, hence the 6V6GTA

    With the 6L6, they additionally did some internal mods to the guts to increase it's power handling, so the newly revised design became the A revision, so we had the 6L6GA. More revisions and beef-ups followed, giving us the 6L6GB and ultimately the 6L6GC.

    STR, depending on who you talk to, stands for "special tube request" or "special test request". Basically what this meant back in the day, is a large OEM customer would request the tube factory to test or tweak an current production tube for a specific operating condition or parameter. Like operating base-up in a high vibration environment, for example. Today, it's just more Mesa BS marketing. Mesa does not make tubes, they just buy them from the usual suspects and put their own labels and nomenclature on them. Mesa resells a couple three different versions of the current production 6L6, so they need a way to differentiate them from one another.
    Looks like you have a bargin there ..and plenty of room for modifing if thats your thing !
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by oc disorder; 07-13-2010 at 09:06 AM. Reason: 'cause I can and incorrect info

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    thx guys thats a start. I dont know much about fixin amps and thats why I bought one for cheap that doesnt work. all I currently know (punn intended) is that the caps could hold energy and not to electricute myself. hopefully with some help I can bring it back to life.

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    Old Timer oc disorder's Avatar
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    The user manual I posted above was the wrong one.
    ( well I did say I'm no Peavey historian ! )
    There are some rather high voltages in there and in the transistorised preamp.
    For starters with nothing on or plugged in check the 5w Ik square ceramic (cerment looking)
    resistor in the power supply.
    As these have no (standby circuit) HT high voltage fuse a short in the output tubes could
    make the 1k go open circuit.
    Also check there is bias (with amp in standby tubes removed) approx -50 volts on both pin 5's .
    Multimeter on DC range negative probe on metal chassis positive probe on pin 5.
    Be very careful and tell someone what you're up to ..to play safe !
    That's two main things should be checked before plugging in new tubes.

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    Lifetime Member Enzo's Avatar
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    Aspen Pittman has been spreading the baloney that GC means "glass container." Well that would be fine until we consider GB. I suppose we could assume that meant "glass bottle." But then what about GA? Um... "glass, ah,I don;t know what" Or maybe "glass around the rest."

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    Senior Member JHow's Avatar
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    theclassic.pdf

    Is it a "THE Classic" ?

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    Lifetime Member Enzo's Avatar
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    To be picky, I'd say no. I think they are saying that the Peavey Classic is "the Classic." Not that the model name has the THE in it. Their Classic is classic, so to speak.

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    Senior Member JHow's Avatar
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    Ah, as in "you shall have no other classics before me!"

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    Senior Member JHow's Avatar
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    You didn't, by any chance, pick this up off of ebay a while back? I bid (unsuccessfully) on one that was also billed as "for repair". Seller was Los Angeles area. It looks really clean. Can't be too far gone wrong. Doesn't look like anybody dropped it off a truck or anything.

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    actually I did and possibly outbid you. My thought process was simple. I wanted to build a tube amp to learn about how to fix them. problem is the cheapest I could find was $245 or so on ax84 and it was a 15w. i thought abought and came up with the idea to find a broken one. Since all my parts are there except for the broken part (parts) I was willing to go up to $200 including shipping so I placed a max bid of $165 (35 shipping) and outbid the last at $145. Recieved it 2 days ago and it is as discribed. Turns on but nothing on the output speakers. gonna start to take her apart after I practice for 45 mins. One thing I did notice when bringing it in was that i could hear the reverb spring bouncing on the chassis. could be broke. not sure if this would stop it from producing sound or not but maybe.

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    Reverb springs normally make racket bouncing around in the tank. Nothing to worry about.....

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    Senior Member JHow's Avatar
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    I think you probably did outbid me. Sounds like you met your budget, though, so Good job! It would certainly fetch more if it worked, and I'm betting you won't have much into it when you get it running.

    Are you planning to just fix as-is, or did you have an idea to implement your own circuit? Strictly speaking, repairing an amp is not the same as building one, and this is hyrbid, part SS part tube.

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    First I would like to get it going see how it sounds. if its not what im looking for then a mod would be in order. I happen to have another peavey 1984 roadmaster sporting 12 tubes and the thing sounds good not to mention its extremely loud 160w head. always like my marshall but Im not a stckler for names just what sounds good for whatever im trying to play.

    Anyway its open I havent tried any tests yet will do tommorrow but it is strange that all that sound comes out of something that looks ridicously simple. Ive included more photos. Not only am I enjoying the challenge Im meeting a bunch of guys who seem down to earth. Rock on








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    Lifetime Member Enzo's Avatar
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    I better go get some dinner, my blood sugar must be low or something. I found myself looking at the screen thinking, "hmmm, that tablecloth would look good as tolex or maybe grille cloth."

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    thats funny enzo. its 330 in the morning and needed a laugh thx

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    Supporting Member TomCarlos's Avatar
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    Special thanks to those who contributed on this thread. I know it is old thread but it came in handy today as I was trying to understand the evolution of the early 70's Peavey Classic Amps.

    A guy in town is selling a Classic B - the second amp in this series. The amp cab appears to be in very rough shape and there are no usable speakers. This one has four inputs (as Enzo mentions in #2 above, Bright, Normal, Series, Parallel). If nothing else, the chassis and electronics could be useful for testing 6L6 tubes!! So that is my question to you ...

    It looks like the Power Amp is fed from the two 10K resistors as seen on the bottom right side of the Preamp schematic. (Sorry, there are no resistor numbers on the schematic). If I was to disconnect that point from the 25uf cap that feeds the two 64278 transistors and install a 1/4" jack there, that would serve as a "Line In" type connection. Agree?

    The other things I would do?

    - Add 1 Ω resistors to the GLG Cathodes and add banana plugs to the chassis - two for measuring the bias current, one for a ground point, and one for the plate voltage.
    - Move/Change the 50K bias resistor to the back of the chassis.

    BTW, I also build a 4 socket bias probe that measures both Plate Voltage and Bias Current but the mods I describe would make it much easier!!
    Attached Files Attached Files

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    Last edited by TomCarlos; 11-03-2019 at 09:09 PM.

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    Stray Cap DrGonz78's Avatar
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    That schematic is not downloading. Here is another to post here...
    Attached Files Attached Files

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    Glad I found this thread. I was able to get one of these classic A & B's off CL recently. Mine is in terrible shape compared to the one in the picture. Someone had shoehorned a different power transformer into the chassis and fried the can capacitor. I've replaced the capacitor but I can't find a transformer # EH 449. I'd like to put the proper transformer in it before I try to power this thing on again.

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    Supporting Member TomCarlos's Avatar
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    Jimmy - The EH 449 transformer (the exact Peavey part) will be difficult to find. You will see them now and then on eBay - also using the identifier 682427. If you were to look for a Hammond replacement, you'll be spending way more than what you probably paid for the amp. In these cases, you might need a "donor" amp - or your amp becomes a donor to fix a different amp. Be patient, keep looking.

    In the mean time, tell us what type of transformer is currently in the amp. Maybe we can see if this is something you can live with.

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    Lifetime Member Enzo's Avatar
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    At least it is an utterly conventional power transformer for a 50 watt amp. about 360vAC HV winding, 6v winding for two 6L6 heaters. ROughly 55v bias winding. Note, bias winding is separate, not a tap on the HV.

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    I see the amp isn't worth much. If I would have noticed the botched transformer install I may have passed on it but I like learning new stuff so now I'm into it.
    Try to understand how the bias winding works. It's not center tapped and one leg goes to ground? I was able to get my head around the other windings I just don't understand bias circuits yet.

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    Big difference in price for the transformer with the separate winding for the bias winding. I'll keep my eyes out for another solution. The Hammond one is way over the top. I might try to use a cheapo import from eBay. Just to get it turned in. https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F20263111 4687

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    Last edited by 76jimmy; 11-12-2019 at 12:14 AM. Reason: Link

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    Supporting Member The Dude's Avatar
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    What transformer is in there now and are you sure that's what fried the cap? Any part numbers on the transformer you have? Maybe it could be made to work?

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    Yes it has two transformers wired up.
    83-611-000 / 130012 = wired to the HV and another set of wires used for fills

    17-7248 / F-46X = being used for bias

    I started to try and figure out what was what and got the FI'ts and decided to just try and find the proper replacement.

    I don't have the scratch paper in front of me but none of my meter readings were even close to what I thought should be there. I'm new to talks forum here trying to figure out how to post IMG.

    Thanks all for any input.

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    Lifetime Member Enzo's Avatar
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    The bias supply is about as simple as supplies get. A half wave rectifier. Your bias supply is a voltage referenced to ground. In the case of bias it is negative voltage. The AC of the winding is rectified, and filtered by caps.

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    Only way I can make sense of things is to apply them to physical real world objects. Now I understand it as a throttle return spring. Had to do some reading last night.

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    Quote Originally Posted by 76jimmy View Post
    17-7248 / F-46X = being used for bias
    \
    Can't find anything about the HV transformer, but if the F-46X being used for bias is the same as this one (https://www.newark.com/triad-magneti...4va/dp/03F1003) I don't see how that one will work for biasing, it won't have enough voltage as it is a 24VAC secondary instead of something like 55VAC as Enzo said above. Seems like you couldn't get sufficient negative voltage to keep the tubes from running way too hot. If someone changed the factory bias circuit to have a voltage doubler then maybe?

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    The HV and heater trans is from a RCA TCS-127 Console TV. The trans used for the bias is definitely insufficient. It's all coming out. Going to give the cheapo import a try. Thanks all for your help.

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    Got it working. Used a Basler Tube Amp Power Transformer 120 VAC 6.3V 6.5A 300-350V 28 VCT BE32901001 from eBay. Had to wire an artificial center tap to the 6.3v winding but it seemed to do the trick.
    Everything works but the tremolo. That's for another night. Thanks everyone for your help.

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