peavey rage 158 question

[guitarsteve07]

I just bought this amp and it turns on, but I can't hear the guitar. It makes a noise when it's on distortion channel and goes quiet on clean but you still can't hear the guitar at all coming through. I've tried different cords, tried guitar on other amo and it works fine. Any ideas? Thanks...

[Enzo]

You have a break somewhere in the signal path. I'd get out the schematic and check DC voltages through the preamp stages for starts.

[guitarsteve07]

schematics

I don't even know how to do/or what you are talking about with pre-amp stages? Can you expand a little bit? Thanks a bunch

[Enzo]

Electronially, this is not a very complex amp. There is a 5-legged thing on the rear edge of the circuit board, that is your power amp IC. Probably says 2040 on it. It is what drives your speaker. Then there is an 8-legged thing in the left rear corner, that is called an Op Amp IC, and is pretty much your preamp. Should say 4558 on it.

Since you get some small sounds when it is on, I am going to guess the speaker works. If you put it on the lead channel and turn up the volume, you get some hiss or noise, right? Let's leave it in the lead channel. I suspect that whatever restores sound to the lead channel will also fix the clean, just a hunch.

Listen to the hiss/noise. Does the POST volume control make it louder and softer? And do the tone controls affect the tone of the noise? How about the Supersat control, does that make it louder and softer?

Each of those things is at a certain point in the system, so if we know which of them still has some effect and which do not, we know how far tghrough the circuit that noise traveled.

Inside, unscrew the metal chassis and slide it out so you can get at the innards. Be cautious. Power it up and hear the noise. Now look closely at the 8 legged thing in the corner, the 4558 IC. Take a small metal object - a tiny screwdriver, a meter probe, a paper clip bent straight - and touch it to the pins along each side. Do you get sound when you touch? It could be loud, so don;t startle. be careful not to touch two legs at once, just one leg at a time. What I really want to find is one or two pins on each side making noise.

Now go to the input jack, front left corner. Right immediately behind it are three little parts in a row - the one on the right is a little smaller and glass. The part in the center of this group is the input resistor. Touch each end of it with your paper clip. Both ends make noise? Either end?

If they make noise, then I suspect your input jack itself. May be broke, or may need resoldering.

[Gilgators]

Inside, unscrew the metal chassis and slide it out so you can get at the innards.

If they make noise, then I suspect your input jack itself. May be broke, or may need resoldering.

I have a very basic question: how do you take this amp apart? I found 3 screws at the back of the amp holding the chassis up. The front is being held in by ... something. Is it just the knobs?

[Enzo]

No, the knobs do not hold it together. They will have to come off to get the circuit board out of the chassis, but you may never have to do that.


I don;t recall this amp specifically, but there are only so many ways to mount one. SOme have four screws down through the top. Some may have some short wood screws through the rear edge, screwed into the wood of the cabinet. One some of the smaller amps - like this one - the two handle screws also hold the chassis in place. See if that works.


Sometimes you have all the screws out and it is stuck anyway. A few things happen. If the rear end of the chassis can move up and down some, then the thing is probably all unscrewed. Sometimes the front of the chassis gets wedged between underside of the top of the cabinet and the top of the grille that covers the speaker. I then may have to pull the screws that hole the front panel out and pop it loose to free the chassis. The vinyl covering on the amp is called tolex. it can stick to the chassis. ALmost like it was glued, but once popped free, it usually never sticks as much. And sometimes the tolex is peeling up from the wood, and the edge of the chassis can catch on it.

[Gilgators]

Thanks for the quick reply, Enzo. I hadn't thought about the handle screws. I'll try those and let you know.

I got the chassis dropped out of my Peavey Classic 30 easier than this Rage ...

[Enzo]

Bring it to Lansing and I'll take it apart for you.

[DrGonz78]

$5 says it is that damn tolex keeping the chassis stuck in the cabinet. Little Crate practice amps have done that same thing to me in the past. Nothing wrong taking off the handle but that is not usually holding the chassis. Some amp handles hold the chassis in like on the Fender 15G. I have taken apart a 158 rage before and think the tolex stuck on to the chassis. It takes some careful finesse prying it loose.

[Gilgators]

Really? That's an incredibly generous offer. If you're available this weekend, I might just take you up on that. I'll try the suggestions you've already given me first.

[Gilgators]

DrGonz, it wasn't the tolex ... but keep your $5. It was the handle screws holding in the chassis. I just unscrewed them, and to my amazement they were about 2" long. They threaded into 2 white plastic clips on the underside of the chassis.

Now, on to the real challenge. My Peavey Rage makes horrible noises when I plug into the Input jack. But if I use the CD jack (in the center), it sounds fine. My guess was a bad jack, and it sure appears to be. The other 2 jacks (CD and Headphones) each have 3 small thin silver tabs on top. They appear to make contact with the metal of the guitar cable. The Input jack only has 2, so my assumption is one broke off.

If that jack sounds like the culprit to you guys, I'll try desoldering and replacing it.

[DrGonz78]

Well I definitely won't be going into a casino anytime soon!!

Anyhow nothing is broken off on the input jack, as it is tip and sleeve(two contacts). The CD and Headphone jacks have three metal contacts for stereo plugs, Tip, Ring, and sleeve. I bet that there is a worn or dirty contact in the jack, or just a bad solder joint on the input jack to the PCB board. $20 says its the solder joints!! lol...'

P.S. I still could lose more money here... It could be a bad connection on one of the pots too. Or just a broken pot... I think the CD input goes straight to the output of the amp, bypassing the preamp section. Anyway when you plug in a cable, does adjusting the pot controls make any change to the sound of this horrible noise?

[Gilgators]

Sorry I can't help fund your casino trip, Doc!

Thanks for helping a relative noob. Now that you mention the 3 metal contacts for the stereo jacks, it makes perfect sense. I'm almost positive the pot controls functioned. For one fleeting moment, the input jack even worked.

This time, I'll put my $20 with yours on the problem being a bad solder joint on the input jack. LOL

[Gilgators]

Another quick question: the knobs on the pots should pull straight off - right? If so, mine are on VERY tight.

[g1]

Yes they should pull straight off. Do not force them as you can pull the shafts right out of the pots and then you need new pots. Sometimes heating them with a heatgun or hairdryer will help.
Unfortunately, if some moron glued the knobs on, you may end up destroying the pots to remove them.