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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

2519.0. "amp fix help needed...." by NAVY5::SDANDREA (What, me worry?) Thu May 07 1992 18:19

    I did another dir/title and did'nt see a repair/technical note.....if
    it exists, would the moderator move this to it's appropriate home,
    please?
    
    Problem:
    
    I broke the fuse holder on my little 20w practice amp.  It was the
    black plastic kind that mounts on the "back plate" of the chassis and
    has a screw on cap.  Radio Shack was out of those so I bought and
    soldered in an "in-line" style fuse holder (the plastic "tube" with a
    wire out of each end).  The amp powers up OK, but it has NO volume!  I
    have to turn it up all the way to get a whisper out of it....it is
    amplifying my guitar signal, but all the power is gone!  What happened?
    Am I missing a ground?  Was the original fuse holder grounded to the
    chassis?  Any suggestions?  My amp is a cheap Korean solid state job...
    
    Steve
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2519.1Hell, if you toast it, you could always go MarshallWEDOIT::KELLYJThink for yourselfThu May 07 1992 19:1011
    If the fuse holder you broke is the style I'm familiar with, it's just
    got an 'in' and an 'out'...no ground.  You can get them locally
    (Boston) at You-Do-It electronics, or through the mail from Active,
    Sager, Newark, Gerber,...  
    
    Curious symptoms.  I assume the gauge of the wire on the replacement
    fuse holder is adequate and that you used the same fuse.
    
    How 'bout risking it and temporarily remove the fuse holder from the
    line?  This would tell you if the new fuse holder and/or fuse is
    causing the problem, but you're temporarily without 'protection'..
2519.2ZYMRGY::samGonna boogie my scruples awayThu May 07 1992 19:253
Radio Shack sells 'em, too...

-- Sam
2519.3RAVEN1::BLAIRWhat *is* it, Man?Fri May 08 1992 12:173
    
    Steve, try re-soldering the connections.  You probably got a cold 
    joint.  Heat the wire, not the solder...
2519.4I'll try these....NAVY5::SDANDREAWhat, me worry?Fri May 08 1992 12:565
    RE: last few...
    
    Thanks guys.....I'll give these few a try....
    
    Stevo
2519.5it's an "open"....NAVY5::SDANDREAWhat, me worry?Wed May 13 1992 13:2915
    I tried the re-solder, checked the fuse rating, etc...everything there
    is ok......
    
    I discovered the real problem when I noticed the amp returned to full
    blast volume when I "flexed" the chassis that holds the circuit board. 
    This guy operates off of 12 volts via a transformer and I was holding
    the amp chassis itself while out of the cab, but the speaker
    connections intact.  I inadvertently "squeezed" the chassis frame while
    the guitar was plugged in and the volume up and WOW!  Anyway, there
    seems to be an open circuit or a defective component that re-connects
    when I "squeeze" the chassis and/or push down on one paricular spot on
    the circuit board.  I'm gonna let one of the techno-geeks at my wife's
    place of employment look at it.....
    
    Steve (Le Dawg)
2519.6look for "cold" solder jointsMEIS::RAMSEYIt could lead to dancingWed May 13 1992 15:1711
Steve,

Look at the solder joints in the vicinity; if they're lumpy or dull or the
solder just forms a ball around the lead, it may be a "cold" joint -- no good
mechanical or electrical contact.  The other possibility is that you've cracked
an etch -- this may be a litttle more difficult to find.

Used to get a gawdawful crackle from my Ampeg until I found the lead from the
input sensitivity switch that wasn't soldered to the board.

Chuck
2519.7Easy to fix when you find it...MANTHN::EDDIt's not *Manhattan*...Thu May 14 1992 08:4312
    These types of failures are usually (a) hard to locate and (b) easy
    to fix. They require more perseverance than skill.
    
    My DEP-5 developed a problem where it would just die, then come back,
    then die. I removed the skins and started poking. After a few hours
    I noticed that applying pressure to the top of one particular cap
    would always bring the unit back. Assuming a bad cap, I removed it
    only to find a broken etch on the PCB. I flipped the board over and
    duplicated the electrical path with a piece of insulated single
    strand wire. Problem solved.
    
    Edd
2519.8EARRTH::ABATELLIWho knew?Thu May 14 1992 11:0815
    re:  .6
    	I'd like to echo the "cold solder joint" reply. I had interesting
    problems with my PV-MX amp when it was powered up for awhile, it'd
    start making these very interesting noises. The noise sounded like
    the tube grids were shorting, so I changed the tubes with new ones,
    but it still didn't fix it! In checking the amp over, I noticed one 
    specific solderjoint (a PTH on the power board) wasn't soldered 
    completely. YIKES! I resoldered EVERYTHING and it fixed the problem!
    Interesting huh?
    
    Take a good look and maybe you'll find the problem yourself.
    
    
    Rock on,
    	    Fred
2519.9good amp repair shopAIAG::WISNERPaul Wisner, TIMA/Stars V3.0 Development, Multivendor Customer ServicesFri Jan 13 1995 16:349
Can anybody recommend a good place to get my amp fixed 
in (or near) Boston?   It's a Fender Suepr 60 - I think 
it just needs some new tubes.  I want a place with a decent
turn around time or a maybe someplace that will give me a 
loaner amp.

How is Wurlitzer in Brighton?

-Paul