Tube Amps / Music Electronics
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|2/14/2003 9:28 AM|
||Crate Vintage club 50 problem|
hi guys, got one driving me crazy.
Replaced the output tubes and put in a known set of good pre-amp tubes.
After about 25-30 min the unit will muffle and some times cut out for a half a second. Sometimes it hiss/crackles for a sec before two to three "muffled" notes and some times the cut out, and then thats it, then it will run ok.(the duration of the practice session)
Cleaned the channel one/two switch and replaced the switching transistor.
It uses an opp amp in the reverb ckt and has a few driver transistors. Where should I be looking? Any one have a schematic?
|2/14/2003 1:37 PM|
I just worked on a friends vintage club 50 with similar symptoms. Half the pots and the input jack had broken solder joints. Damn pc mounted crap.
Decent sounding amp though.
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|2/15/2003 1:14 AM|
I had checked all that. Re soldered a bunch anyway...but that didn't help. I don't care for that "buzzy" distortion...reverb kinda weak..
|2/16/2003 12:10 AM|
don't use high gain...don't use reverb
|2/15/2003 2:03 PM|
Check the bypass contacts on the effects loop jack. If I recall that one has a single TRS jack for the loop. Take a spare TRS plug and wire the tip to the ring. Plug that into the jack. If sound is restored, the jack is the problem. I keep my shorting plug on the bench to troubleshoot exactly this symptom. A lot of dirty insert jacks show up on mixers too.
On the jack, you can measure with a meter the resistance across the three sets of contacts. SHould be zero ohms. If it measures over half an ohm, it is dirty and will cause trouble. The circuit still works with a couple ohms resistance, but those ohms are indicative of poor contact.
If it is not the loop, then signal trace through the amp. APply a signal to the input and see what happens stage to stage - follow with your scope.
|2/16/2003 5:14 PM|
Check the bypass contacts on the effects loop jack. If I recall that one has a single TRS jack for the loop. Take a spare TRS plug and wire the tip to the ring. Plug that into the jack. If sound is restored, the jack is the problem.
Ive worked on a few of these as well and seen that exact same problem and the FX jack was the culpret in both cases. Enzos advice is is right on the money
I buy CRC contact cleaner (quick drying formula no#02130)
from Home Depot for cleaning these jacks and it works well and will NOT melt plastic too.
|2/16/2003 2:38 AM|
I know you're looking for VC-specific help, but have you worked your way through R.G.'s magic Tube Amp Debug page? http://www.geofex.com
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