Resurrected Peavey Triumph 60

[stokes]

Me and a friend of mine each bought this amp back in the late '80's.Fortunately I traded mine soon after for a Boogie.I have had his amp on my bench more times than any amp I have ever seen.Soon after buying it,while still under warranty,he started getting intermittent oscillations.Sent it back twice and both times they said it was fine,nothing wrong with it.He gave up on them and gave it to me I found a leaky coupling cap in the PI.It was okay for a few years and then the same thing,after a half hour or so it would start oscillating,another leaky cap.I had already changed 3 over the years and he just bought it back again,guess what?Another leaky cap,this time it was a 1k volt coupling V2A to V2B,so now I'm in the process of changing every cap I havent changed already.No wonder they stopped making these.They do sound great,but what crap parts they used.

[Lostfollicles]

Hi Stokes

Remember they are now over 30 odd years old which must say something for them as there are still around but I guess they were built to a price! Plus they do have quite a high HT at nearly 500 Volts well! 486 on mine!
I was thinking of substituting all my coupling caps for Zoso's/Mustards or equivelents but I'm not sure it's worth the expense or the trouble as I don't like the clippy crunch/ultra channels, way too much fizz it's certainly no "Orange or Marshal" not even Fender come to think of it!!
Still thinking of dumping mine on some other poor sod!
Regards
Lostfollicles

[nashvillebill]

Well, I would take it off your hands to experiment with it if the price was right, ...but you're in Spain right? That wouldn't be cost-effective....shipping would be quite $$

[stoneattic]

Should I be concerned that my plate voltage is only 453V versus the 500V shown on the schematic?

[nashvillebill]

What's your voltage measured from C42+ to ground? (chassis ground, not C42-)

This is DC but there will be ripple on it.

[stoneattic]

I'll have to check it next time I get a chance to work on it, likely Friday. The 453V was measured using my Amp-Head bias tester.

[stokes]

Hi Stokes

Remember they are now over 30 odd years old which must say something for them as there are still around but I guess they were built to a price! Plus they do have quite a high HT at nearly 500 Volts well! 486 on mine!
I was thinking of substituting all my coupling caps for Zoso's/Mustards or equivelents but I'm not sure it's worth the expense or the trouble as I don't like the clippy crunch/ultra channels, way too much fizz it's certainly no "Orange or Marshal" not even Fender come to think of it!!
Still thinking of dumping mine on some other poor sod!
Regards
Lostfollicles

Sure,but the problems started when the amp was less than a year old.A couple of those coupling caps were rated for only 400 volts and had more than that on them.With the right tubes and some tweaking they can sound very good,tho.Built like crap,damn that profit margin.These amps dont lend themselves to experimentation and modding,not with the way those PCB's are stacked and most of the components underneath the board.

[nashvillebill]

Okay, I modelled the crunch/ultra preamp with LTSpice. While it does accentuate the midrange, it's not as peaky as I thought it might be! This plot is from 80 Hz to 8000 Hz. Max reading is around 66 dB if you can't read it.

Note, my amp did not have R98 or C63. And this is with the clipping diodes CR1 and CR2 jumpered out.

This plot assumed a flat input coming from the tone controls. It's just the preamp section in the crunch/ultra. And this assumes I drew everything correctly and ran the simulator right.

[Lostfollicles]

Hi Bill
My T60 also does not have R98 & C63 either!
Do your V4 & v5 Tubes get too hot to touch like mine? The heater voltage AC is 6.14 Volts which I think is OK!
Would these tubes get hot if V4 & V5 cathode caps are leaky?
V1-V2-V3 have 6.73 Volts DC which I think is OK aswell!

5 years ago I changed all the power supply caps and replaced all the supply diodes to: BY127 (higher inverse voltage type) but I'm beginning to think part of the reason for this amp sounding so bad is leaky cathode caps and coupling caps! Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah!
This beasts gotta go!
Regards
Lostfollicles

[nashvillebill]

Mine get pretty warm, I've got the amp apart now for converting it to a head (it was a combo) so I can't fire it up. Leaky cathode caps * might* make them run hotter, I'm no expert.

When I was running the Spice simulations, I tried changing cathode cap values. and definately there is a change to the response curve. It sure wouldn't hurt to change the coupling caps and cathode caps.

Oh when I did the simulation that generated the plot that I posted above, I had included R97 in the circuit, by mistake. Mine doesn't have R97 either. Removing R97 and re-running the sim did increase the mid peak slightly, by maybe a dB, and shifted the treble response to the left a very little bit. However, this sim was done assuming both the pre-and post- volume pots at maximum volume. I didn't have time to play with various combinations of volume pots.

I was able to flatten the response curve a lot in the sim by removing C21, removing C17, increasing C13 (note, edited from my orignial typo when I wrote C23) to .022, and changing C15 to 22. Bass response in the new curve was pretty flat, treble still dropped off early (down -3 dB at maybe 1500 or 2kHz). But I strongly suspect this would NOT be desirable, the increased bass in the gain stages would likely sound "farty". LTSpice doesn't take overdriving tubes into account...I don't think...

It took me a day to figure out LTSpice and how to use it, it's free (Google for the url). The tube models are at Duncan's amp pages.

[Lostfollicles]

Mine get pretty warm, I've got the amp apart now for converting it to a head (it was a combo) so I can't fire it up. Leaky cathode caps * might* make them run hotter, I'm no expert.

When I was running the Spice simulations, I tried changing cathode cap values. and definately there is a change to the response curve. It sure wouldn't hurt to change the coupling caps and cathode caps.

Oh when I did the simulation that generated the plot that I posted above, I had included R97 in the circuit, by mistake. Mine doesn't have R97 either. Removing R97 and re-running the sim did increase the mid peak slightly, by maybe a dB, and shifted the treble response to the left a very little bit. However, this sim was done assuming both the pre-and post- volume pots at maximum volume. I didn't have time to play with various combinations of volume pots.

I was able to flatten the response curve a lot in the sim by removing C21, removing C17, increasing C23 to .022, and changing C15 to 22. Bass response in the new curve was pretty flat, treble still dropped off early (down -3 dB at maybe 1500 or 2kHz). But I strongly suspect this would NOT be desirable, the increased bass in the gain stages would likely sound "farty". LTSpice doesn't take overdriving tubes into account...I don't think...

It took me a day to figure out LTSpice and how to use it, it's free (Google for the url). The tube models are at Duncan's amp pages.

Woah! What schematic are you working to Bill?

C23 on mine is a 22uf cathode electrolytic on V4a changing that to a .022 wouldn,t be wright me thinks!!

I took out C17 in mine too! But C21 is there "so I'm told" to help stop clicks on the channel switching relay! and doesn't do anything for the tone!!

I'm thinking of changing C13 to .022 like C16 and cathode cap C15 to a .68uf also thinking of trying lower values in R31 & R27 to tame the gain! Maybe trying a 470K in R27first and if that doesn't tame it, I might try a 100K in R31 or even the other way around?

As for the tone charts thing I wouldn't know where to start! But thanks anyway!

All of the mentioned mods are going to have to wait until I can earn some spondoolicks or sell some songs! All I need now is a lyricist! lol

Regards

Lostfollicles

[nashvillebill]

Oops, I fat-fingered my typing. C13, not C23, exactly as you thought. Changing C15 didn't do a lot until it really went up in value, like over 2uF, I believe.

I think when I played with a couple of resistor values, they actually made the mid peak worse.

[nashvillebill]

Here is the response curve for these mods:
-cut out C21 (I don't think this affects channel switching)
-cut out C6
-changed C13 to .022
-changed C15 to .68

Also this has the pre/post volume pots set at 25%. And it has been corrected to remove R97. The C15 change did little.

[nashvillebill]

Let's try these mods insted:
-cut C21
-cut C17
-change C13 to 0.022
-change C15 to 2.2
-add two bypass resistor, each 100 pF. The first bypasses R12. The second bypasses R29. This yields the response curve here. Note the extended treble and slightly enhanced bass response.

edited: corrected circuit mistake, changed simulation plot accordingly.

[Lostfollicles]

Hi Bill
I love all of these tweeks your doing and the graphs are very impressive but I suppose at the end of the day it's down to what it sounds like when you put it all back together!

You will be the only amp guy that I know of apart from amp techies (who charge lots of money) that has bothered to tweek this amp and pass on your findings! I have no doubt all your hard work will be loved and greatly appreciated by all the owners of these amps, especially if you can tame the beast and make it what it should have been in the first place had Peavey bothered!

Enzo has also been very helpfull regards this amp!

Good luck bill and be safe!

Regards

Lostfollicles