Fix it or junk it? How serious is this problem?

[TimWilson]

First, I know that even expert electronics repairmen can't accurately evaluate the seriousness of a problem without seeing it in person... I'm just looking for general info:

My amp has what's been guessed to be a 'cold solder joint failure'. Basically, the amp works great for an hour or so, then goes mute. The power stays up, and the signal chain through to the DI out still works, but it doesn't make it through to the amp output. I have moderate repair experience, and I've looked closely at the board, but I can't find the weak spot.

I love this amp. I don't want to replace it for what seems like a simple problem. But I can't trust this thing on one more gig!

So what I'm asking is this: How hard is it, typically, for a real repairman to find and fix a cold solder joint failure? Is it a simple thing with the right tools, or a needle-in-a-haystack expedition that'll cost more than the amp ($500-$700 range)?

Any info will be appreciated.

[JimmyM]

Cold solder joints aren't very expensive to fix. Most will fix it for a one hour bench charge, and it usually doesn't take them too long to find it. And you can can ask to be called first if it's not a cold solder and is going to cost more than a cetain amount to fix.

[TimWilson]

Originally Posted by JimmyM

Cold solder joints aren't very expensive to fix. Most will fix it for a one hour bench charge, and it usually doesn't take them too long to find it. And you can can ask to be called first if it's not a cold solder and is going to cost more than a cetain amount to fix.

Thanks, Jimmy. I feel better about dropping it off at a shop now. I appreciate it.

[pbagley]

You don't mention what amp is giving you problems, and I don't see an amp listed in your profile. In my very limited experience cold solder joints crackle and pop, and do not fail quite the way you describe. I'm wondering if there is a different heat related problem. I've heard of people needing to reattach transistors to the heat sinks, and I've heard of the thermistor failing and causing thermal shutdown at lower then specified temperatures. A good repair guy will check these things and catch the problem quickly.

Good luck! Let us know what the problem was when you find out.

[seamonkey]

Your best bet is a tech, and this is probably what they do first.

You can buy a can of air or use a nozzle from a air compressor. When the amp heats up and turns off blow air around to see cooling off of what part brings it back to life.

[T-Bird]

Hi.

+1 for the make and model of the amp.

Originally Posted by JimmyM

Cold solder joints aren't very expensive to fix. Most will fix it for a one hour bench charge, and it usually doesn't take them too long to find it. And you can can ask to be called first if it's not a cold solder and is going to cost more than a cetain amount to fix.

That's kind of correct assuming there's only one troublesome solder joint, the amp is relatively simple and the tech and the owner are just half-assed and too cheap to reflow every solder joint on the PCB's.

OTOH, fixing one problem at a time for a reasonable fee will keep this easy job coming in again and again . Perhaps the owner even gives it to the tech for free, out of sheer furstration.

Originally Posted by seamonkey

You can buy a can of air or use a nozzle from a air compressor. When the amp heats up and turns off blow air around to see cooling off of what part brings it back to life.

Pair that cooling air with a hair dryer to heat the parts/PCB first, and you're one step closer to a proper troubleshooting method.


BTW, doesn't sound like a cold solder joint to me either, more like a cracked PCB trace. TOTAL PITA to find on a crowded board.
Easy(ish) to fix though assuming a single or double sided PCB.
Multilayer, forget it.

Regards
Sam

[JimmyM]

Point taken, Sam. Still, that's not super expensive to do, is it?

[T-Bird]

Hi.

Originally Posted by JimmyM

Point taken, Sam. Still, that's not super expensive to do, is it?

IME it's directly proportional to the complexity of the amp and the amount of the joints.

Fortunately, on the wave-soldered boards, one can usually assume that the thin component leads are more properly soldered than the thicker ones.

A clear difference can be seen IME on the boards made before the ban on lead in the solder and on the boards made right after the ban.

Also, on the boards soldered by hand, there's often visual clues as of which areas were badly soldered and which were done well.

Unfortunately, even 2 hours on the bench is often too much financially for modern amps, and that's a real shame.

Fortunately, the trouble shooting of cold solder joints is pretty straight forward (minding the SAFETY as always of course) and the re-flowing or re-soldering is pretty easy, so even an average DIYer is able to handle it.

Regards
Sam

[calebbarton]

If the amp has an effects send/return, try plugging a cable into both of those after the amp has failed to put out sound. I bet you are dealing with dirty contacts there, if not a different unrelated to solder joint problem.

Start there, if that does not solve the problem......sell it.

[TimWilson]

TB is an every day treasure trove of precious info! Thabnks again, brothers.

My amp is a Peavey T-Maxx 210 combo. It's long since out of production, but before this problem popped up, let me just rise up and testify: This little sucker brought the thunder like the giant tri-amped wall 'o bass amp that it replaced never could. The dual preamps (tube/ss) and super fine graphic make this an amazingly versatile little guy. By far the best bass amp I ever lugged around (and I've lugged a lot). I know Peavey amps don't get a lot of love, but this one gets all of mine. It'll be very disappointing to hear that a repair will be more expensive than it's worth, or impossible.

I'll take it to the area expert tomorrow, after trying that send/return suggestion above. THanks again, guys.