Advice on Tube Amp Serviceability

lthan07 · #1 07-25-2010, 08:23 AM

Ok so I am new to this forum. I was directed here by a really helpful guy on the Strat-talk forum and said there was a lot of helpful amp guys that really know their stuff. In my case, I acquired a Peavey Mace 320t 2x12 for free. Someone was throwing it out so I decided to grab it and fix it up. Speakers work fine and tubes seem to be looking good as well (dim orange color and slightly blue with standby off). The damage is definitely from the inside of the chassis. It has every possible symptom (hum, scratchiness, pops and crackles..) and something is definitely loose inside of it. I first thought about selling it for quick easy cash but only offer I got was $60 and let's face it; this thing is a 160 watt monster with six 6L6 tubes, pure headroom heaven. Kind of a lowball offer. The guy on Strat-talk advised me to show people here the schematics of my amp to see how easy or how hard it would be to service my amp by a tech. I'd really appreciate any help with this. Thanks

http://www.schematicheaven.com/newam...e_deuce_vt.pdf

jnewmark · #2 07-25-2010, 09:17 AM

I'm no amp tech guy by any stretch of the imagination, but alot of what you describe sounds like dirty pots and cold solder joints, something a tech can easily fix. You are getting sound out of it, right?

RickenBoogie · #3 07-25-2010, 09:25 AM

+1 just take it in to a qualified amp tech, and have it looked at. Even if it cost you $150 to fix, still a bargain, right?. Don't poke around in there yourself, it can kill you. Also, don't play a bass through it, (after it's fixed, assuming it's a guitar amp), unless you keep the volume down.

lthan07 · #4 07-25-2010, 10:01 AM

Yeah I'm definitely not in the mood to get zapped by those capacitors so I'll leave it to the pros. jnewmark, I am getting sound of it. When I turn it on, there is a lot of hum and scratchiness whenever I mess with the controls. But when I do find a "sweet spot" with the pre/post gain knobs, the hum significantly reduces and the guitar sound actually comes out. But any slight movement of any of the controls or any budging of the amp causes the loose thing inside the chassis to move and the hum comes back along with more popping and crackling.

will33 · #5 07-25-2010, 10:16 AM

The DIY part of this would be to get a can of De-Oxit and clean every pot, jack and switch in there. Also look for any obviously bad solder conections and freshen them up. Talking about solder connections on pots, jacks, etc. I wouldn't mess with caps, resistors or any of those components, leave that to the pro's but you should be able to do that much without touching anything dangerous. That should take away a lot of the scratchiness. It may still have some problems that you need a real tech to fix but doing that much yourself should eliminate some of the basics and probably lower your bill some at the tech.

As stated before, be careful, don't touch any of the other parts, just do the pots, jacks, switches, fuse holders, etc. You can look at the other parts to see if anything is obviously burned or loose but that's as far as I'd go.

nysbob · #6 07-25-2010, 10:20 AM

If you're going to use it for bass (and there's no reason not to) you should think about ditching the cab and just mount the head in a box. That head will sound nice through any decently efficient cab.

LevinFan · #7 07-25-2010, 01:52 PM

Quote:

Originally Posted by lthan07

Ok so I am new to this forum. I was directed here by a really helpful guy on the Strat-talk forum and said there was a lot of helpful amp guys that really know their stuff. In my case, I acquired a Peavey Mace 320t 2x12 for free. Someone was throwing it out so I decided to grab it and fix it up. Speakers work fine and tubes seem to be looking good as well (dim orange color and slightly blue with standby off). The damage is definitely from the inside of the chassis. It has every possible symptom (hum, scratchiness, pops and crackles..) and something is definitely loose inside of it. I first thought about selling it for quick easy cash but only offer I got was $60 and let's face it; this thing is a 160 watt monster with six 6L6 tubes, pure headroom heaven. Kind of a lowball offer. The guy on Strat-talk advised me to show people here the schematics of my amp to see how easy or how hard it would be to service my amp by a tech. I'd really appreciate any help with this. Thanks

http://www.schematicheaven.com/newam...e_deuce_vt.pdf

I wouldn't sell it. Get it fixed

BassmanPaul · #8 07-25-2010, 04:23 PM

Your link did not work for me.

Paul

LevinFan · #9 07-25-2010, 04:39 PM

Here is the link Paul....
http://www.schematicheaven.com/newam...e_deuce_vt.pdf

BassmanPaul · #10 07-26-2010, 10:32 AM

Thanks for the link. It's a SS amp with a tube output stage. Running at the plate voltage it does I'd say about 140-150W. Should run reasonably well for bass. I would probably go the custom head case route but try the amp out before you go that far.

Paul

lthan07 · #11 07-26-2010, 10:57 AM

I'll be playing guitar with it. Looking at the schematics, is there any way to tell whether this amp is easy to work with or not? And what would be the benefit of turning it into a custom head?

nysbob · #12 07-26-2010, 11:04 AM

Well, you're posting on a bass forum, so my assumption was you were going to use it for bass.

As such the open back 12" would be about useless.

Carry on.

BassmanPaul · #13 07-26-2010, 11:04 AM

If you are using it for guitar use it as is. The tube section is about as simple as it gets. The driver and control circuits are SS mounted on PCBs. It should be fairly easy for an experienced tech to work on.

Paul

seamonkey · #14 07-26-2010, 11:40 AM

It's a freak.
It's not "All Tube" which is going to bother those looking for "All Tube"

You can source all the SS parts at digi-key.com, it would be easy to fix, but don't hot-rod it, it might hurt any value it has.

Restore it and sell it as a missing link in the history of combo amps.
Line-6 does a SS modeling pre-amp now with tube output section, but to have an original might be worth it to some collector.

There's a "cap of death" on the polarity switch - get rid of it.

BassmanPaul · #15 07-26-2010, 11:45 AM

Quote:

Originally Posted by seamonkey

There's a "cap of death" on the polarity switch - get rid of it.

And install a three core power cable. Sorry I assumed that would be an obvious first step! Thanks Seamonkey.

Paul

Passinwind · #16 07-26-2010, 12:06 PM

Quote:

Originally Posted by seamonkey

don't hot-rod it, it might hurt any value it has.

The first version of these amps (or maybe both, can't remember at this point) benefit greatly from uprated driver transistors, in my experience. It's been a few decades since I worked on one, but Peavey factory service should still know all about it.

Sell it to a Skynyrd tribute band and get something nice sounding instead with the money.

lthan07 · #17 07-26-2010, 01:06 PM

Thanks for the help guys. The amp already has a three prong cord for it which is good. Passinwind, I've been trying to do exactly that; selling to a hardcore Skynyrd fan trying to recreate that tone. But I haven't seen anyone showing interest in it and there's no way I'm giving it up for $60. If I do get it fixed, how would its market value be? I heard that Peavey resell values aren't that high even for an amp made famous by Skynyrd :/

bertbassplayer · #18 07-26-2010, 03:08 PM

I have the Deuce which is the 120 watt version. Resale for these things are HORRIBLE. You'd be lucky to get anything more than $200 out of it. I've tried to sell mine in the past and the most I've gotten offered is $100.

As for repair it sounds like all that might be wrong with it is just some dirty pots, that can be easily reminded by some contact cleaner from Radio Shack. If you still have issues you can then decide if it's worth it or not to have it fixed.

lthan07 · #19 07-27-2010, 08:47 AM

Yeah I will end up just the DIY repair and see how it goes. I sure hope that's all that's wrong with it and nothing like moisture damage (the day I found it on the street we had light rain). I'm really dying to see what this amp sounds like

lthan07 · #20 07-28-2010, 06:03 PM

Ok so I tried to do some work on my amp today. I plugged it in first to see which pots actually needed some cleaning but it seemed like none of them did. All the knobs worked fine with no scratchiness though the amp did give out a loud constant hum. Also when I played through it, everything sounded out of tune. It was like a muted talk box effect and even when I played notes chromatically they would sound completely off and not to mention the hum got unbearable by the end of it. Any thoughts?