'82 800 2203 problem

honkytone · 08-12-2012, 07:39 PM

I have an '82 jcm800 2203 with a technical problem.
After warming up for a minute or more I can switch on the standby, play for 5-10 minutes, sometimes an hour then out of nowhere comes this extremely loud squeal that sounds as though the amp will blow up at any moment.
Now the tubes are all Mesa pre 12ax7's and the power tubes are Mesa 6550-A's. They've probably been in there for a few years but I see no sign of them overheating and the caps all look good.
Does anyone have advice? Should I replace all tubes first then caps?
I mean what in ur expert opinions do the symptoms reflect as the problem?
Thanks in advance! Honkytone

honkytone · 08-12-2012, 09:06 PM

Get it teched with new tubes/caps?

honkytone · 08-12-2012, 09:07 PM

Just seems the tubes are fairly new and the caps show no signs of crappin' out.

honkytone · 08-12-2012, 09:10 PM

? is what tends to make the amp just start screaming bloody murder out of no where?

honkytone · 08-12-2012, 09:18 PM

Any advice much appreciated.
I lost my old tech last year to kidney failure and his protege is nowhere near as knowledgeable. He just wants to charge me out-the-ass to retube and cap the amp.

mickeydg5 · 08-12-2012, 10:49 PM

That does not seem to give anyone much to go by thus far. Five to ten minutes or sometimes an hour are big differences. Try to duplicate the problem and see if if there is a common cause. Sometimes a faulty input jack can cause an uncontrollable squeal if the conditions are right.

honkytone · 08-12-2012, 11:03 PM

Will check the jacks. Thanks for ur reply!

Hollowbody · 08-13-2012, 01:22 AM

Even if it is not the cause of the squeel I would still replace the filter caps if they are original. A halfway decent tech should be able to knock that out in no time for a nominal price. It's tempting to talk you through it, starting with ordering the parts and draining the caps etc.. but getting a pro on it may be the best decision.

I would replace the tubes as well or at least try to find someone to test them. Some testers are better than others. Emission, shorts , gas testers. Others are dynamic testing and some measure only transconductance, so finding competence may be tedious depending on where you live.

But troubleshooting that issue is probably priority.

80sTone · 08-13-2012, 06:45 PM

Try posting this in the workbench group....May get even more insight

Beefcake · 08-13-2012, 07:42 PM

I had this issue on an 800 4212. Turned out to be a faulty input jack.

Lowdown · 08-14-2012, 04:03 AM

Jack,cords,pedals...trial by elimination is the first and foremost way to go before taking it to a tech.

Try a different cord with a different guitar,direct. No pedals. Turn all dials,guitar and amp...

Just because the glass is new does not exclude it. Do you see any arcing/glowing? Try swapping them around...

08-12-2012, 07:39 PM	#1 (permalink)
honkytone Junior Member Join Date: Dec 2011 Location: In the swamp. The anus of America. Posts: 10	'82 800 2203 problem I have an '82 jcm800 2203 with a technical problem. After warming up for a minute or more I can switch on the standby, play for 5-10 minutes, sometimes an hour then out of nowhere comes this extremely loud squeal that sounds as though the amp will blow up at any moment. Now the tubes are all Mesa pre 12ax7's and the power tubes are Mesa 6550-A's. They've probably been in there for a few years but I see no sign of them overheating and the caps all look good. Does anyone have advice? Should I replace all tubes first then caps? I mean what in ur expert opinions do the symptoms reflect as the problem? Thanks in advance! Honkytone

08-12-2012, 09:06 PM	#2 (permalink)
honkytone Junior Member Join Date: Dec 2011 Location: In the swamp. The anus of America. Posts: 10	Re: '82 800 2203 problem Get it teched with new tubes/caps?

08-12-2012, 09:07 PM	#3 (permalink)
honkytone Junior Member Join Date: Dec 2011 Location: In the swamp. The anus of America. Posts: 10	Re: '82 800 2203 problem Just seems the tubes are fairly new and the caps show no signs of crappin' out.

08-12-2012, 09:10 PM	#4 (permalink)
honkytone Junior Member Join Date: Dec 2011 Location: In the swamp. The anus of America. Posts: 10	Re: '82 800 2203 problem ? is what tends to make the amp just start screaming bloody murder out of no where?

08-12-2012, 09:18 PM	#5 (permalink)
honkytone Junior Member Join Date: Dec 2011 Location: In the swamp. The anus of America. Posts: 10	Re: '82 800 2203 problem Any advice much appreciated. I lost my old tech last year to kidney failure and his protege is nowhere near as knowledgeable. He just wants to charge me out-the-ass to retube and cap the amp.

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08-12-2012, 10:49 PM	#6 (permalink)
mickeydg5 Senior Member Join Date: Sep 2011 Location: US of A Posts: 3,643	Re: '82 800 2203 problem That does not seem to give anyone much to go by thus far. Five to ten minutes or sometimes an hour are big differences. Try to duplicate the problem and see if if there is a common cause. Sometimes a faulty input jack can cause an uncontrollable squeal if the conditions are right. Lowdown likes this.

08-12-2012, 11:03 PM	#7 (permalink)
honkytone Junior Member Join Date: Dec 2011 Location: In the swamp. The anus of America. Posts: 10	Re: '82 800 2203 problem Will check the jacks. Thanks for ur reply!

08-13-2012, 01:22 AM	#8 (permalink)
Hollowbody Senior Member Join Date: Jan 2009 Location: Tulsa / Northern Texas. Posts: 2,087	Re: '82 800 2203 problem Even if it is not the cause of the squeel I would still replace the filter caps if they are original. A halfway decent tech should be able to knock that out in no time for a nominal price. It's tempting to talk you through it, starting with ordering the parts and draining the caps etc.. but getting a pro on it may be the best decision. I would replace the tubes as well or at least try to find someone to test them. Some testers are better than others. Emission, shorts , gas testers. Others are dynamic testing and some measure only transconductance, so finding competence may be tedious depending on where you live. But troubleshooting that issue is probably priority.

08-13-2012, 06:45 PM	#9 (permalink)
80sTone Member Join Date: Nov 2011 Posts: 61	Re: '82 800 2203 problem Try posting this in the workbench group....May get even more insight

08-13-2012, 07:42 PM	#10 (permalink)
Beefcake Junior Member Join Date: Mar 2009 Posts: 3	Re: '82 800 2203 problem I had this issue on an 800 4212. Turned out to be a faulty input jack.

08-14-2012, 04:03 AM	#11 (permalink)
Lowdown Member Join Date: Dec 2009 Posts: 99	Re: '82 800 2203 problem Jack,cords,pedals...trial by elimination is the first and foremost way to go before taking it to a tech. Try a different cord with a different guitar,direct. No pedals. Turn all dials,guitar and amp... Just because the glass is new does not exclude it. Do you see any arcing/glowing? Try swapping them around...

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