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Conference napalm::guitar

Title:GUITARnotes - Where Every Note has Emotion
Notice:Discussion of the finer stringed instruments
Moderator:KDX200::COOPER
Created:Thu Aug 14 1986
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:3280
Total number of notes:61432

1491.0. "Pro Reverb amp problem" by WMOIS::S_BRYSON () Thu Sep 21 1989 13:19

    I have this mid 70's Pro Reverb that's perplexing me.  I'm getting
    this high pitched hum only when the volume(s) is turned up (audible).
    I've tried fooling with other guitars,  outlets,  matching output
    tubes,  cords,  grounds,  ect.  My drum machine causes no problems.
    The preamp tubes are approx. 6 months old and the output tubes approx.
    a year.
    
    Ideas?
    
    Thanks in advance for any suggestions,
                                              Steve
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1491.1Some thoughtsCSC32::MOLLERNightmare on Sesame StreetThu Sep 21 1989 14:3222
	My twin reverb had a similar problem. The fellow I bought it
	from had dropped it off the back of a pickup truck & it was
	not improved at all by the experiance (It has Altec 12's that
	weigh in at about 30 lbs each). Needless to say, I got it cheap.

	After building a new body for the electronics & speakers & 
	assembling it all, I found the same problem, but it went away
	if something that was grounded properly was plugged into the
	jack. It turned out to be a bad solder joint between the steel
	case and the PC board (you need a big soldering iron to re-heat
	this joint). Of course my steel case was bent when I got it,
	so I have a good idea why this solder joint was bad.

	You might also have a bad ground of some sort if the problem only
	occurs when you plug something in. Does this only happen when
	certain things are plugged in or when nothing is plugged in or
	no matter what is/is not plugged in??

	You might try re-heating all of the contacts on the PC board/jacks/
	pots with a soldering Iron.

							
1491.2DNEAST::PUSHARD_MIKEThu Sep 21 1989 15:145
    If it occurs all the time,check out the power supply for bad filtering.
    
    
    Mike
    
1491.3ASAHI::COOPERInsert Flipper-type P-name here...Thu Sep 21 1989 15:168
    Yeah, what he said, and also look for wires flopping around inside
    the case that seem to be routed a little close to the transformer
    and power tubes.  You can cement these things down with blobs of
    silicone gel (comes in a tube. Makes for extra insulation, ya know?

    Hope this helps a little,
    
    jc