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Common Crate VC Problem??

9/2/2003 2:29 AM
Kobbs Common Crate VC Problem??
I've had, currently have, will probably have in the future Crate VC 30's (various models) with what appears to be a common problem, and I'm hoping a common solution. There are the volume ups and downs, however, these tend to be fixed with a major solder joint overhaul... However, what sometimes remains, and I can't seem to find the specific problem, is a hiss/static/low level distortion that creeps in to the sound of the amp after it warms up... I know this is common, but as I stated before, looking to see if anyone knows a common solution... particularly weak cap, dressing, etc. etc.???  
9/2/2003 4:37 PM
Jack Collins

I don't know the answer to your problem offhand...  
I'd start troubleshooting by pulling the preamp tubes one by one, starting with the ones closest to  
the input and listening for when the static goes  
Once you've isolated it to a particular stage  
probe with your chopstick, measure voltages etc.  
in that particular area. Give the socket for that  
tube a good cleaning with some deoxit.  
A likely suspect would be a failing plate resitor.
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9/2/2003 8:06 PM

check the bypass capacitors, and the caps in the reverb section.  
9/3/2003 5:05 AM

By far THE most common cause of levels being erratic or intermittant on amps in general, is the contacts on the effects loop jacks. Patch a cord from send to return on the loop jacks and see if the sound restores. If so that was the trouble. Clean the contacts or replace the jack. I use a small burnisher on th contacts and almost never have to change the jacks.  
No effects loop? Same test for power amp in jack and preamp out jack.  
ANother thing I see mostly in Crate amps is the amp wanting to switch channels all by it self now and then. This is almost always the footswitch jack. The contacts that close when there is no footswitch get dirty or oxidized and they don't work. Clean them or replace the jack.
9/9/2003 3:52 AM
Thanks for the ideas, escpecially the FX loop, would never even have thought about it... Good idea for the future too, depending on the loop... I had a "similar" problem on a fender (dare I say it out loud) red knob "The Twin", where the loop level switch was full of crud and caused all sorts of eratic problems...  
Thanks, I'll let you know the results...  
9/13/2003 6:25 PM
Just wanted to thank ENZO as it appears that the effects loop jack is a BIG problem, both in being dirty and solder joints. Greatly appreciated for opening my eyes to the "simple" stuff...  
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