Resurrected Peavey Triumph 60

[nashvillebill]

I have (hopefully) wrapped up my repairs on this amp. Back two or three months ago, there were several folks posting with problems on theirs, which were kinda similar to what I found. So here's a summary of what I did...hopefully this will help somebody out in the future.

First, about the amp. This amp is all-tube, with a pair of 6L6GC's for output. There's a 12AX7 for the PI, a 12AT7 for the reverb driver, and another 3 12AX7's for various gain stages. It's listed as 3 channel (clean, crunch, ultra gain) though the 3rd channel is merely a different gain setting on the crunch side. It dates back to the late 80's and apparently it got quite favorable reviews back then. Mine's a combo with a 12 inch Scorpion speaker, and like all older Peavey amps, it weighs a ton. There's diode rectifiers and one transistor--it drives the standby LED. Channel switching uses relays.

My amp already had the crunch channel diodes-bypass mod and the EQ-enable mod. (These are detailed in the Harmony Central reviews).

The symptoms: Fluctuating power/gain outputs. Gain was sometimes nonexistant, other times deafening. Reverb cut out. And the hiss, even at idle, was quite unbearable.

My goals: first, repair the problem areas. Second, make it reliable. Third, remove the hiss if possible. I was generally pleased with the tone when the amp seemed to work right, so after thinking about it a while, I didn't see a need for any "tone" mods. I gave up on the idea of adding a choke on the PS or adding screen resistors.

...more in my next posting...

[nashvillebill]

Ok, first let's see what problem areas there were. Oh boy, this amp has 4 PC boards, stacked, with Molex connectors. The Molex connectors were the insulation-displacement kind, which means the wire is pressed into a V-shaped clip that cuts through the insulation and presses into the wire. The sharp V had cut the reverb return wire in two, hence the reverb issues.

I decided to hard-solder all these connections--remove the Molex end and solder the wires directly to the pins on the PC boards. However, this will make future service difficult, so I needed to fix everything else before putting it all back together.

The tube sockets looked rather worn, so I bought new porcelain sockets. I also replaced all the switching relays...now on to the electronic components...

[nashvillebill]

The electrolytic capacitors were over 20 years old. Definately time to replace them, if the replacements last 20+ years as well I'll be 70 years old and repairing this amp probably won't be important.

NOTE: This amp is VERY tight for space. It is CRITICAL that the replacement caps are not any bigger (particularly their height). I found this out the hard way.

I was not sure if there were any problems with coupling capacitors, but given the volume issues, I decided to replace all caps that had high-voltage on them.

Another note: the PC traces lift off rather easy. I used solder-wick but still had ocasional issues.

Now on to hiss reduction...This is one area that I did just as an experiment and I don't know if it was necessary. I suspected the factory resistors were carbon, so I went in and replaced most every resistor that was in the signal path, including plate resistors. I used big honkin' metal films, 3 watt at some places. But size is an issue with these too, 1 watt was all that'd fit in some areas.

Ok, all done with replacing parts. Let's add a bias trim pot off to one side. (I suspect I shoulda used shielded wire for this). I replaced the first bias resistor with a 3.3k and used a 100k multi-turn pot.

Ok, let's fire 'er up.

[nashvillebill]

Sine wave looked good (after I remembered to turn on the sig gen...a few anxious moments). Let's try to set bias by eliminating crossover notch...what crossover notch? The amp had Sovtek 5881WXT's and it was really hard to discern a notch. So I shunted the output transformer and set to around 40 mA with 500 volt plate voltage. Funny, the other side measred only 32 mA...maybe the tubes aren't balanced.

Let's try tweaking by looking at the scope again...no notch, no notch, now a BIG notch...what's this, I've been turning the trim pot the wrong way and the tubes are glowing BRIGHT RED! Oops. Back to using the OT shunt and set back to the 40/32 reading I had before.

I guess the Sovteks are pretty tough, when I plugged the speaker in, they still worked. But still a LOT of hiss. Let's play a while...sounds fairly good, all functions work, let's turn it off and come back tomorrow.

[nashvillebill]

Okay, next day. Turned it on...low volume again, and no gain. WTF? Even more hiss than usual. Then, after a few minutes, the gain came back up and it functioned normally, albeit with hiss at idle. WTF? Let's try again the next day to see if it repeats. Oh, and let's get new 6l6's to see if that improves the hiss.

Yep, same thing. Low volume and no gain when cold. Still lots of hiss. OK, let's go back into the basement and check a few things. Plate voltages--good. Heater voltages on two preamp tubes--good. Heater voltages on remaing preamp tubes--only 4 volts DC. WTF? Let's look at the schematic, yep they rectify the heater voltage to DC for the first three gain stages.Let's put the scope on the heater supply for those 3 tubes--gee, that's a terrible looking sawtooth--and it's only 60 hz.

No diodes handy, but I had a couple of bridge rectifiers. I mounted a 25A bridge rectifier on the side of the PC board and ran a few inches of jumper wires. Bingo, heater voltage now close to 6 volts, 120 hz with not a lot of ripple. Oh, and the power tubes now almost even on current draw.

Plug 'er in...hiss noticeably improved. Volume and gain now fine. I suppose the low heater voltage meant it was taking a while for the tubes to heat up enough to work.

As a final measure, I used some copper conductive tape (from Stew-Mac for shielding guitar cavities) to wrap the bias trim pot wires, and also I covered the inside top of the wood cabinet to provide a tad more shielding.

I'll use this at band practice tonight and hopefully gig with 'er next weekend. If she continues to work correctly, I may separate this into a head/speaker cab to make it more manageable to carry.

This was not an easy amp to work on, I wouldn't recommend a complete beginner to begin his/her amp repair education on it. But if someone has moderate troubleshooting skills and basic electronic knowledge, it was pretty straightforward.

[Patrick Lau]

Okay, next day. Turned it on...low volume again, and no gain. WTF? Even more hiss than usual. Then, after a few minutes, the gain came back up and it functioned normally, albeit with hiss at idle. WTF? Let's try again the next day to see if it repeats. Oh, and let's get new 6l6's to see if that improves the hiss.

Yep, same thing. Low volume and no gain when cold. Still lots of hiss. OK, let's go back into the basement and check a few things. Plate voltages--good. Heater voltages on two preamp tubes--good. Heater voltages on remaing preamp tubes--only 4 volts DC. WTF? Let's look at the schematic, yep they rectify the heater voltage to DC for the first three gain stages.Let's put the scope on the heater supply for those 3 tubes--gee, that's a terrible looking sawtooth--and it's only 60 hz.

No diodes handy, but I had a couple of bridge rectifiers. I mounted a 25A bridge rectifier on the side of the PC board and ran a few inches of jumper wires. Bingo, heater voltage now close to 6 volts, 120 hz with not a lot of ripple. Oh, and the power tubes now almost even on current draw.

Plug 'er in...hiss noticeably improved. Volume and gain now fine. I suppose the low heater voltage meant it was taking a while for the tubes to heat up enough to work.

As a final measure, I used some copper conductive tape (from Stew-Mac for shielding guitar cavities) to wrap the bias trim pot wires, and also I covered the inside top of the wood cabinet to provide a tad more shielding.

I'll use this at band practice tonight and hopefully gig with 'er next weekend. If she continues to work correctly, I may separate this into a head/speaker cab to make it more manageable to carry.

This was not an easy amp to work on, I wouldn't recommend a complete beginner to begin his/her amp repair education on it. But if someone has moderate troubleshooting skills and basic electronic knowledge, it was pretty straightforward.

Hello, I am new to the repair/Mod on tube amp, and lucky I saw your post here and guess you may help on modding this amp
I've got this amp NOS and did both diodes-bypass mod and the EQ-enable mod already. I like all three channel's voice but I really can't stand it's sharing the same EQ on all three channel! you ever think of adding EQ or, if it's possible to add EQ on this amp?

about the tube, this amp's on fixed bias- and I know nothing about bias setting, so is it difficult to fix it out and use EL34 or 5881?

Thank you so much!!

[Gtr_tech]

EQ pedal in the FX loop? Quick, dirty, easy. If ya wanted ta get tricky with it you could build a circuit to activate 3 different EQs that come on/off with each channel. Not all that hard, but there will be some engineering involved. Start with the Motorola small sigal transistor databok (jfets).

[Enzo]

If you want separate EQ controls for each channel, it would not be technically difficult to do, but you need to answer one question first - WHERE would you put the controls?

[Gtr_tech]

I was thinking an outboard box with whatever EQ circuitry needed built into it.

[nashvillebill]

I dunno about any other tubes, but the previous owner had put Sovtek 5881WXT's in mine in place of the factory 6L6GC's. I baised them about the same as for a 6L6GC since that's (kinda) what they are. Eventually I went back to 6L6GC's.

I would not put any other 5881's in there. The plate voltage is too high I believe for the old style 5881's...and I'd be leary of trying to convert to EL34's. Different pin connections and the heaters draw a lot more current, I believe.

The power tube sockets are on a very cramped PC board, so modifications are challenging. Same with the other boards, space is very very tight.

Though I'd love to have separate EQ for each channel, I agree with the others, an outboard EQ would be much more feasible.

[Enzo]

Don;t worry about 5881s, anything they make these days that says 5881 on it is just a 6L6 in disguise.

[Gtr_tech]

Maybe the "re issue" Tung Sol 5881 is exempt. I dunno....haven't tried them. They s'posed to be closer to the real deal.

[Patrick Lau]

Thank you so much for all responses!
I've took the amp part out from the combo and making a chassis for it.
that's fine to add extra control without much worry!
I've studied some info from AX84 about the tone circuit, not really difficult to make it! just wonder where's to place it for the Church and Ultra channel

I've got the stock "Peavey Super 6L6GC" in the amp. I've ordered GT's matched pair and I didn't check it before paid and a second before I plug in the tube!! I found it's not 6L6GC but 5881! but I found no problems with them?!

Do you all think I need to set the bias or it's OK?

Here's Hong Kong early in the morning and later tonite I will have some cap job on it~ Hope I discharge it right and possible to reply tmr!

Thank you again!!

[nashvillebill]

I'm certainly no expert on the 5881's, but everything I've read agrees with the others. The "new" 5881's such as the Sovtek 5881WXT are basically 6L6GC's but Idon't know about the other 5881 re-issues.

I was merely cautioning though about paying big money for an old set of 5881's, such as NOS Tung-Sols, since I don't think the older true 5881's are rated high enough.

Peavey's fixed bias is good enough to slap a pair of the Sovteks in there without any problems IMHO, again that's what mine had when I bought it. The bias may not be "optimum" but it'd work fine...

[KrisKross]

Peavey Triumph 60

Hi Nashvillebill, you sound like you could advise me.

I have a mint condition PT60 that's been in storage in the house for the last 16years unused (long story) pretty much since new.

It functions perfectly, but I'm not ecstatic with some of the tone I get. I understand that by bypassing the CR1 & CR2 diodes gives great results, but I want to change the tone a bit by dialing into the 80's Marshal/Vox vibe and swapping out the Scorpion speaker with something like a Celestion G12-65.

The ratings seem to match, but I read that the G12-65 tho' is supposed to work best in a 4x12 cab setup and not on its own? What would you recommend here?