5150 Advice needed from Amp Gurus

[decoy205]

Instead of necro posting one of the trillion 5150 issues threads I started my own, as every situation is slightly different, bare with me on this long post.

I’ll give you the history on my experience with the Block Letter I have.

Bought used from Harmony Central forum 2007 ( I know first mistake) I figured it would have issues but I would probably get it serviced anyway so I took the risk.

I used it with NO issues for about a year. It was noisy but worked fine. I never used the FX Loop just the Channel switch for going to cleans. It’s an aftermarket switch with what I believe to be a cheap Hosa TRS cable.

I starting using it again in 2009 and at a rehearsal the volume cut out and only the pre worked. I changed the power tubes and it seemed to do the trick. These were Ruby tubes that the seller gave me when I bought the head so I just used what I had. I used it for a show or two then it sat for a while. When I went to use it again it started cutting out again. The channel switch made the Post knobs not really do anything. It got a little louder but I was able to turn them all the way up. Typically that would be way too excessive as I rarely get past 4 on the post.

I tried the FX loop cleaning trick, jumping the effects loop, etc. nothing really worked. It made the crackling sound when flipping the standby switch on and off.

I brought the amp to Fuchs Audio. (Andy Fuchs) which is local to me.

They had the amp a week. I didn’t give them the footswitch. They changed the power tubes, changed 1 pre-amp tube as it was the wrong type(it wasn’t a 12ax7), and they cleaned all the pots and jacks and I’m guessing the tube sockets. I can’t remember what it was. The thing sounded huge, and much more quiet than before. I took it home fired it up and did a little testing. The footswitch seemed to cause problems. I thought it was the switch itself. So I unplugged it. Used w/o the switch it was fine nice and big sounding no issues. But only a few times.

Last night I wanted to try and integrate a Boss Noise suppressor ( I don’t have a decimator yet) and a TS9 into the amp and use the 4 cable method with the FX loop. I didn’t like the way it sounded so I put everything running back through the front except my delay pedal. I hit the FX loop to engage the delay pedal to test it and then bam the volume drop issue began again. Weird noises when taking it on and off standby. Then it doesn’t get loud and the FX loop is useless. I immediately unplugged all pedals and went direct from guitar to amp. And the issues didn’t go away with or without the footswitch plugged in. It still switches channels but sounds crappy either way.

I’m going to bring it back to Fuchs this time with the footswitch. I am covered under their service guarantee so hopefully it won’t cost me again. But I still have some questions before I do this:

- Do you have to keep cleaning FX loop jacks all the time, and the remote jack as well? Will this help? Should I try this again?
- Can these issues be permanently fixed or is this just the price you pay for owning this amp?
- Is the FX loop just useless and I’m better off going through the front with my pedals? I’m thinking of getting a decimator and that would need the FX loop.
- Is there anything I can suggest to Fuchs to help the fix this problem
- What footswitch and cables should I be using with this amp? I don’t have the original, should I get one like they have on ebay or locate a Peavey OEM type, or that would not be the issue so keep using the one I have.

This amp gives me the tone I want when it works.

Here’s what it sounded like two weeks ago. A little muddy but it’s the mic placement/eq. I did this quick and dirty after I installed a new pickup in my V.

http://dl.dropbox.com/u/49386838/ASYLUM CLIP W. DRUMS 6.27.m4a
http://dl.dropbox.com/u/49386838/ASYLUM CLIP NO DRUMS 6.27.m4a

​

Thanks guys.

-John

 

[JakeAC5253]

The footswitch controller for the 5150 is a simple continuity switch, from tip to ground, and from ring to ground. It sounds like you may be eating through phase inverter/fx loop buffer tubes (V4 and V5 respectively), or you might have an intermittent output transformer internal short on the primary, or even a shorted filter cap. Luckily two out of those three things is relatively cheap and easy to do.

 

[decoy205]

The footswitch controller for the 5150 is a simple continuity switch, from tip to ground, and from ring to ground. It sounds like you may be eating through phase inverter/fx loop buffer tubes (V4 and V5 respectively), or you might have an intermittent output transformer internal short on the primary, or even a shorted filter cap. Luckily two out of those three things is relatively cheap and easy to do.

Thanks for the response Jake!
Fuchs only changed 1 preamp tube. I'm not sure which one it was. Should change all the pretubes?

I'm assuming the output transformer issue would be the costly one.

Where could a shorted filter cap likely be? I can tell Fuchs to check for that.

 

[JakeAC5253]

Fuchs only changed 1 preamp tube. I'm not sure which one it was. Should change all the pretubes?

Sure, why not. Nothing bad can come of it, and it's a relatively cheap mod.

I'm assuming the output transformer issue would be the costly one.

Bingo.

Where could a shorted filter cap likely be? I can tell Fuchs to check for that.

It's part of the power supply. They should know where it is. Only trouble with the 5150's is finding replacements of significant capacitance while also constraining to the size requirements of the chassis, which means a relatively small or flat shaped cap, while most typical filter caps tend to be longer or taller.

 

[sprack]

There are only 2 caps on the board that are hard to source externally. Peavey has all of them if you just want to replace with stock values.

My guess is that the non-12ax7 tube they replaced was in the phase inverter. Like Jake said, it's probably a good idea to retube the preamp. Just don't put a Tung-sol in the phase inverter.

Did you try the FX-loop bypass on the new issue? Might be the effects loop driver, but obviously if this fixes it, its dirty jacks.

 

[AceFireForce117]

I'm looking for a peavey 5150, but all these problems with the amp make me doubt, especially the fact that it's always the same thing (volume dropping, fx loop related problems). I hope you get your amp fixed and pumped up real soon ! The tone is just so awesome.

 

[decoy205]

Thanks for all the responses guys. Just FYI I bought this amp used and I'm sure it wasn't treated the best prior to my ownership. It worked when I bought it but I knew it would need to be services. Anything is fixable. So I just gotta find the issue. I think it may be a bad loop tube. So I'm gonna try that first.

I did try jumping the fx loop again but that's not it. Fuchs cleaned all pots jacks and sockets so I'm almost positive it's not dirty.

I really appreciate the comments.
-John

 

[AceFireForce117]

^ Hey whenever you find the issue with your amp please keep us informed

 

[decoy205]

I looked at the pre tubes. I'm not sure which one was changed by Fuchs. The V1 was wrapped in some sort of rubber? I figured I would change one by one until it made a difference.

I put an EH 12ax7 in the V1 socket. Tested the amp again and now everything is working even the FX loop. I feel like all the pre tubes should be changed. I got these extra tubes from the previous owner so I dont know their history.

I'm going to order all new pre tubes and change them all. Seems like the right thing to do. I think that should do the trick. If something is still wrong at least it will rule that out.