Are Amps With Printed Boards Harder To Fix?

fat_fleet

fat_fleet

Swollen Member
I just got my 4x10 Blues Deville back from a tech I've used a couple times. He says the noise it's making is tough to diagnose and probably not worth it to fix... I'm a numnuts with electrical stuff but I think what he was saying is there are a lot of these coupling capacitors (?) of different ratings that are tough to check and pretty much have to be swapped out one at a time and finding the bad one could take hours. He basically said the amp's had a good life, but it's seen better days and it might be too old to get rid of the noise that's buggin me cheaply.

These amps came out in the mid-90s so it's not even 20 years old. To me that doesn't seem old for an amp. But it's got PCBs and my question is, if it was handwired/point-to-point, would it be as tough to fix? People use and maintain amps all the time that are older than this one. I ask you folks cuz I deeply suspect it's a stupid question and don't want to ask the tech. I have no shame with y'all.
 
Last edited:
I'm regret to inform you that your tech is a hack or just lazy. Find a different one. PCBs started showing up in amps in the very early 70s. Maybe late 60s even? They're fixable.
 
It won't be capacitors. Wannabe toob technicians always get a massive erection at the thought of charging $$$ to do a cap job, and those caps rarely go. It'll be a plate load resistor; start with the phase inverter and work your way back to the input stage.
If you had to test the capacitors, you could with this; http://www.ohio.edu/people/postr/bapix../TO-5_3.JPG. But again, it's pretty rare. For some reason, I've changed more plate load resistors in one year than I've changed capacitors in the last ten years.
 
fat_fleet said:
I think what he was saying is there are a lot of these coupling capacitors (?) of different ratings that are tough to check
Click to expand...

Looks like the schematics are out there on the interwebs.

If one cap needs replaced, it seems sensible enough to them all, right?
A beginner could do this, with the schemo.

That's if caps are even the problem. ;)
 
I wish I knew enough about amp repair to help you out, but I do know that regular Joe's mod and fix their own PCB amps all the time. Get on a Fender forum or amp repair forum and ask around.
 
Yeah I have a couple other guys I can take it to get a second opinion if I want. And I'm definitely not gonna start fishing round in there myself right now. I'm really more interested in people's opinions about long-term life and maintenance of PCB vs PTP.

Actually reading about it now. Didn't realize how well-worn this debate was when I made the thread!
 
fat_fleet said:
Yeah I have a couple other guys I can take it to get a second opinion if I want. And I'm definitely not gonna start fishing round in there myself right now. I'm really more interested in people's opinions about long-term life and maintenance of PCB vs PTP.

Actually reading about it now. Didn't realize how well-worn this debate was when I made the thread!
Click to expand...

Long term life is not an issue. There are tons of 70s PCB amps still kicking out the jams.
 
fat_fleet said:
I don't know jack about any of this but I'll bet a 70s PCB is easier to work on than a 90s one...
Click to expand...

That depends on the amp. My 1979 JMP 2204 is a PCB, there's nothing in there. My Plexi reissue is a 2001, it's got a PCB, and there aint jack shit in there. My JVM is a 2011 and it's like NASA designed that thing inside. So it just depends.
 
Although there's no guarantee that a capacitor swap is what you need, electrolytic capacitors DO tend to leak and dry out after years of use and the symptom of this happening is often noise.

If you're paying big money to an engineer, maybe it's not economic to fix them (other than as a labour of love). However, if you're willing to buy the parts and teach yourself to solder, caps are one of the easier things to do and great practice.

Beware dry joints!
 
I had a hot rod deville. First time it made that crackling noise a tech charged me $150 bucks to put a circuit board in it. It worked fine for a year.

God awful static noise came back. I wasn't going to put more money in the amp so I took a soldering iron and remelted every single solder joint on the amps circuit boards. It worked like it was brand new again for about 4 months...hello same old problem.
I reflowed all the solder joints again but this time no cigar.

My advise: reflow the solder joints and if that fixes it...
SELL THAT SUMBITCH!!

It it dosen't fix it use it as a speaker cab.

Its a cheesy piece if shit design that heats the circuit board and resisters up too much.
Don't put one nickle in it.
 
jimistone said:
I had a hot rod deville. First time it made that crackling noise a tech charged me $150 bucks to put a circuit board in it. It worked fine for a year.

God awful static noise came back. I wasn't going to put more money in the amp so I took a soldering iron and remelted every single solder joint on the amps circuit boards. It worked like it was brand new again for about 4 months...hello same old problem.
I reflowed all the solder joints again but this time no cigar.

My advise: reflow the solder joints and if that fixes it...
SELL THAT SUMBITCH!!

It it dosen't fix it use it as a speaker cab.

Its a cheesy piece if shit design that heats the circuit board and resisters up too much.
Don't put one nickle in it.
Click to expand...


You're pretty much confirming what I think here, though it's not really a crackle and I tried to leave out specific details about the actual problem in the original post to avoid any kind of diagnostic discussion.

But as long as we're here, it's more of a low distorted buzz that's always the same volume (doesn't swell with the note). Sounds almost like a speaker coil rattling away, but I know it's not speaker related. It might not even be audible with louder, more overdriven guitar parts..but I use this amp mostly for cleans and keep it below the point of breaking up. The tech actually replaced a lot of the tone stack and called me saying it was "mostly" fixed, but I went down and plugged in, it just sounded the same to me. I actually had to turn the amp down to point out the sound. I think it would still be a good amp for someone else, but it's just not cutting it for me any more.
 
Try Reflowing the solder and sell it. The problems will keep on a coming. Guitar center won't even give you a half way decent trade on one in good working order.
They've probably had tons of them to bounce back.
Those amps are money pits and although they sound pretty good fender should be ashamed of putting their name on such a problem plagued peice of gear.
 
Anything is fixable, but one of the problems with, or advantages of, cheap amps is that they are disposable. It will cost you more to have a tech replace half the componants trying to fix the problem than it would cost to just get a new one.

I would vote for using it as an extention cabinet for your new amp.
 
You must log in or register to reply here.
Back
Top