Peavey XXL repair!

[ohmy!!]

So I scored a Peavey XXL head for $75, but the kicker is there's something wrong with the power section.  The guy I bought it from said a tech quoted him $60 to fix it so I was hoping it's nothing too major like the autoformer that's in there. I've not really worked on solidstate heads much so I'm going to need some pointers on what's up with this.  The preamp works fine, I'm running it into my Heritage VTX's poweramp (which I just fixed prior to getting the xxl  :tu: ) at the moment. It sounds good through it, but I would like to fix the head due to the fact that it has this nice power switch on the back so I could kick it down to 25watts to practice in my bedroom late at night.  Here's what's going on though.  It doesn't output any sound through the speakers.  When I turn the volume up all the way and set it to the ultra channel though I can hear it very very faintly playing (and whining type of sound), but not through the speakers, something in the head itself possibly the autoformer? I don't know if that's possible but yeah that's what's going on, seems really odd.  Any ideas from anyone out there?  I've got no clue where to start.  Usually checking the fuses is the first thing if there's no sound I thought, but they're all fine.

[joecool85]

First thing to check is if the speaker is actually any good.  Check that and let us know what you find out.

[bry melvin]

could kick it down to 25watts to practice

The VTX low power mode goes down to 22 watts...but still vey loud...Does this one work differently?

[ohmy!!]

I dunno what the VTX goes to on low power, i know on high power it's 130W.  That isn't the point though, the point is I want to fix the head.  But yeah even on the low power mode it's real loud and if I want to play at night and not bother roommates even 22W of tube power would be way too much.

[ohmy!!]

Oh and the speakers are good, that's what plugged into the VTX.  I figured I'd fix the XXL and if I liked it with the proper power section I might even sell the VTX and buy a speaker cab or two to go with it.

[J M Fahey]

The guy I bought it from said a tech quoted him $60 to fix it

Your *best* bet, by far, is get that tech and pay him those $60. No kidding.

[ohmy!!]

Seeing as is it was a long distance transaction that's not an option lol.  I guess I can always throw and attenuator at it to drop the volume without losing the tone.  You can't just turn the volume down on the master volume on the XXL, your sound just turns to garbage.  Either that or run a good pedal into it when I need to play it low.  I just thought it'd be nice to fix it if I could figure out what's going on with it. 

[Enzo]

What is this autoformer you refer to?   As far as I know, this amp has a plain old power transformer.

This could be a million things.  A bad thermal sensor, a loose wire, and bad impedance switch, etc.


You might not be able to send the amp to the same tech as the guy had, but there are good competent techs all over the country.

[ohmy!!]

Well it has an output transformer like a tube amp would, to give it a more tube-like tone I guess.  Peavey called it an auto-former when I asked for a quote on the price when I asked them incase I needed to replace it ($78 btw).  I guess because it's an output transformer that's switchable on wattage, not sure how it all works.

[ohmy!!]

Yeah there's a local amp tech I know around here, he's kind of a dick though and basically tells you to buy a new amp if you have a Peavey.  He did that a couple years ago when I had asked him about my Heritage VTX and told him what was going wrong with it (turns out it needed new filter caps).  But yeah he had told me it was a junk amp and that he was working on one not long before that "it was designed by some crackpot engineer who decided to make and amp that doesn't make any sense and blow tubes every 10 minutes."  Said he wasn't even going to finish working on the other guy's amp and told me to sell it for parts and buy something better like a Mesa or a Hughes and Kettner.

[Enzo]

Any "tech" who dismisses entire brands of gear out of hand like that doesn't deserve the title "tech" in my book.  Drive a little further and find someone worth a damn.   Just because he doesn't understand the Heritage doesn't mean it is not a fine amp that thousands of people enjoy and rely upon.   If the heritage design is crackpot, then so are most of the Music Man amps that Leo Fender made.

I didn;t realize the XXL had a transformer on the output.  it is a solid state amp, and doesn't need the transformer.  The transformer may contribute something to tone, or might do nothing more than offer full power out at different impedance loads, but nonetheless, we can remove it and connect a speaker directly to the amp output for testing.  it will be the last thing I would suspect either way.  The connector to it is far more likely to be trouble than the transformer itself.

For a tech problems like "dead" and "zero sound" are actually usually easier thing to fix than "smoke" or "distorted."

[ohmy!!]

Alright, so I should be able to disconnect the output transformer and still be able to get sound out of it? 

[phatt]

Hi ohmy,
            Hazata guess try the efx loop trick.
i.e. Loop a lead from Efxout to return.
just fixed an early Peavey special last week (has the auto tranny like yours)
the loop switch contacts where shot.

If no luck then Go with Enzo's thoughts,, You need to establish a Real connection to the power amp output.
if it's like the one I worked on then several switches/ connections happen between poweramp out and speaker.
Phil.

[J M Fahey]

Hi ohmy. A few things :
1) Sorry, I assumed it was an across-the-town deal.
Anyway, you should already know that the most-popular-EBay-phrase is "it doesn't work, but a technician told me it's very easy to fix, for only (insert a very low amount here)" :grr
Car salesmen use the variant: "this car was previously owned by a sweet senior lady, who only used it to go to Church on Sundays" ... and you find a forgotten CD on the player by "Chainsaw Homicide Cannibal Killers" ... :grr
2)Please stick to the amp in question; I was led to believe (until I Googled it) that it was a tube amp, with all that talk about "1/4 power mode", using it "loud because the master sucks", and even mentioning "tubes" .
3) That said, start by testing the loop or power amp in with a known good audio source, as suggested above.
4) Write/call Peavey and ask them for that circuit/schematic.
They're great guys and back what they do.

[ohmy!!]

Hi ohmy,
            Hazata guess try the efx loop trick.
i.e. Loop a lead from Efxout to return.
just fixed an early Peavey special last week (has the auto tranny like yours)
the loop switch contacts where shot.

If no luck then Go with Enzo's thoughts,, You need to establish a Real connection to the power amp output.
if it's like the one I worked on then several switches/ connections happen between poweramp out and speaker.
Phil.

Yeah there's a little board that has the output jacks as well as a few switches to change up the Watts, tightness, and ohm selection for the speakers.