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Crate GX-60 squealing issue... please help

Started by DIYmastermind, September 10, 2013, 06:02:08 AM

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DIYmastermind

Well i have very recently joined this forum. recently as in, a couple minutes ago. i've tried a couple other forums (which will remain nameless) in which the people were very nasty. made (or tried to) make me feel stupid for using incorrect termanology, even when they knew exactly what i was talking about. i have been searching the net for an amp related forum with friendly, knowledgeable people, who will attempt to help me. not attempt to make me feel little. so, i found this forum, and read through some posts that interested me, and this forum (and the people) seem to fit the bill. now, to the amp in question.

The amp in question is a Crate GX-60 that was given to me by my next door neighbor. it had been his rig for quite some time and (i believe) was manufactured and purchased in the mid 90's. i was told that in the last couple of years the amp had started dying on him. upon further investigation (google is your friend, haha) i found numerous people saying Crates GX series was prone to reliability issues. my neighbor's complaints were that the amp just stopped working, period (he never went into detail, but i believe what happened to him is happening to me now). and he had stopped even trying to play through it for the last 6 months.

With everything he said in mind, i carried the amp home and began dissecting it. i pulled the amp loaded chassis from the cab and used compressed air to get everything that was calling the inside of the cabinet home, out. i inspected the amp itself, looking for bad caps, blown fuses, etc. everything looked to be in working order, so i reassembled and took it inside to see if it worked. i fired it up and put a G chord through the clean channel. it worked, and pretty darn fine too. the only thing i found that could be slightly percieved as "stopped working" in my hour or so of playing through it, was that on both channels the volume would sporadically increase and decrease on its own. either a slight increase, or a nearly complete decrease, where the amp could barely be heard. any advice on a fix for this?

Anywho, fast forward a couple of months. i turned the amp on and began to play. everything was fine, until out of nowhere it started squealing (i mean really squealing, enough for a temporary loss of hearing) like a stuck pig. immediately i unplugged it and the head scratching began. i pulled the chassis and inspected it for bad caps, blown fuses, etc. and again, everything looked fine.

so here i am today, asking for advice. how do i get this amp back in working order? i have since pulled the amp loaded chassis from the amp, turned the speaker cab into an 8 ohm extention cab for my amp heads (i don't own a 12" speaker cab at the moment, and the "Crate Special Design" speaker sounds good IMHO), and given up on the amp. but the amp had a good clean channel, NICE spring reverb, and took pedals like a BOSS (pun intended haha). i love fixing things, it's a passion of mine to take things apart, figure out how they work, and when i can, make them better then what they were. how do i get this bad boy back in working order? my goals are to get it to quit squealing, and fix the issue of self fluxuating volume. PLEASE HELP!

p.s. please don't advise me to buy another amp, scrap it for parts, or anything like that. i have other amps, better sounding ones (IMO). FIXING things is what i love. with that said, i hope everyone here is friendly and helpfull. and i hope to have a good time recieving and giving knowledge and advice to those in need.

J M Fahey

The idea here is to repair things, but that means troubleshooting, one way or another.
You will have to be our eyes there, test what you are told to, and answer what's asked.
Too sleepy now to be of any help, but will re read this later.
I'm sure others will chime in too.
Welcome to the Forum.

Roly

G'day @DIYmastermind, welcome.

We have been known to correct terminology, but only to dispel confusion so we are all on the same page.

Quote from: DIYmastermindused compressed air to get everything that was calling the inside of the cabinet home, out.

The biggest thing I've ever found in an amp was an eight foot Diamond Python, and I don't think any amount of compressed air would have helped.   ;)



"Fine fine, you just move out when you are good and ready; I'll just get on with something else..."

{While these guys can bite they are actually quite placid and make good pets.  I had a wild one that would visit every mouse season and clean the place up, liked to curl up on top of my big old computer monitor and watch me work, nice and warm.}


Okay, the most common cause of problems are sockets.  These gets dirty and go intermittent, and they get wrenched when somebody trips over a cable and damages the solder joints to the Printed Circuit Board (PCB).

So from what you have said a good starting point is to give the sockets, Input and Fx Send and Return where fitted, a good clean with metho or a proper contact cleaning product such as DeOxIt.  Once wet with cleaner you work a plug in and out quite a few times to scrub the contacts.

The Input and Fx sockets often also contain switching contacts that perform related functions such as muting and signal bypass, and when these get dirty and don't make reliable contact some very strange things can happen.  Like squealing.

This amp has "Line In" and "Line Out" which are likely to perform the same way as Fx Send and Return, that is they will likely have bridging contacts to carry the signal across when nothing is plugged in.  One test trick is to plug a known good lead between these two and see if it changes anything.  Wiggling these, and the input plug, may show some physical sensitivity and help to locate where the trouble is occurring.

We are not just interested here if the fault goes away, but any change that would indicate that its physical, and that we are close to it.  Once we are pretty sure we have eliminated these common dirt related problems we can then have a close look for electronic problems, but the majority of amp problems, in fact problems with electronics in general, are due to dirt and can be fixed by some appropriate cleaning.
If you say theory and practice don't agree you haven't applied enough theory.

DIYmastermind

#3
Hey roly, thanks for the welcome :) that's a pretty large snake! Let's be glad they're more afraid of us then we are of them, or that amp might have been the end of you! The worse thing I have ever found in an amp was a yellow jackets nest about the size of both my fists balled next to each other. And that's the story of how I discovered my allergy to bee stings! But hey, you take the bad with the good when the owner of a junkyard is a family friend, and let's you take most anything you want.

As for constructive criticism, I am ALL for that! That's what i love about all of this, there is always more to learn. But there's a fine line between that and being rude, insulting, and arrogant.

back to the amp. what is metho? As for DeOxIt, I've heard of it and know what it is, but I have no idea where I'd be able to get some. What about an electronics store like RadioShack?

Roly

Actually Pi (what else do you call a Python?) was pretty social, as they mostly are.  Had quite a bit to do with them, only been struck at once and I was asking for it, but overall very easy to get on with.

Yeah, I do most of my "shopping" at the local tip; junk shops, garage sales - the amount of good stuff people throw away!

I can certainly do "rude, insulting, and arrogant" if I'm poked hard enough.

Quote from: DIYmastermindwhat is metho?

Methylated Spirit, methyl alcohol; or isopropyl or rubbing alcohol, or quality vodka if your budget runs to it - two for the amp, one for me.  ;)

You have to watch out for "contact cleaner" 'cos some of these products contain more oil than cleaner.  Apart from being flammable, metho is safe on just about all plastics and components, but it does need to be fresh and kept well corked because it is quite hygroscopic and will leave moisture behind when it evaporates.  By all means check out what your local electronics stores stock in the way of contact cleaners (generally in pressure pack cans) but be suspicious of anything that says it "lubricates" or "displaces moisture", and attracted to anything that says it is specifically contact cleaner, and evaporates quickly with no residue.
If you say theory and practice don't agree you haven't applied enough theory.