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K200B-1 Losing power when warm [message #17930] Thu, 20 December 2012 00:24 Go to next message
BC
Messages: 583
Registered: March 2000
Location: Kentucky
Senior Member
The title tells most of it. I have a B-1 I use at rehearsal and tonight after about an hour of constant use it started losing volume and distorting a bit when pushed. I am guessing something has gotten warm and is failing. The amp remained audible for playing after I increased the volume but, it really sounded pushed. I am using it with a 4 ohm Altec 421 2x15 cabinet so that should not be a problem. Where should I look first. Forgot to mention I had the channels tied together through the input jacks. Do I have an output trans problem? Thanks! Cool

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Re: K200B-1 Losing power when warm [message #17931 is a reply to message #17930] Thu, 20 December 2012 06:35 Go to previous messageGo to next message
pleat is currently offline  pleat
Messages: 1453
Registered: June 2004
Location: Belding, Mi
Senior Member
BC, I'm no tech, but I'd check to make sure the diode that clips on the power transistor heat sink is still in place.
I had an amp do the same thing, the longer it was on the lower the volume. I snapped it back into the spring clip and haven't had a problem since.
pleat

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Re: K200B-1 Losing power when warm [message #17932 is a reply to message #17930] Thu, 20 December 2012 06:38 Go to previous messageGo to next message
stevem is currently offline  stevem
Messages: 4748
Registered: June 2004
Location: NY
Senior Member
BC, jumping the channels is not a problem may first thought would be a solder connention going bad an or the thermal/bias doiode has popped out of its clip down point inbetween the output transistors.

You may want to slip the amp out of the case and apply some heat with a hair dryer on low, in this way you may atleast be able to pin down what section of the amp has the problem.

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Re: K200B-1 Losing power when warm [message #17933 is a reply to message #17932] Thu, 20 December 2012 08:56 Go to previous message
BC
Messages: 583
Registered: March 2000
Location: Kentucky
Senior Member
This amp recently failed and I found the fuse connection disconnected at the solder point at the switch. Maybe I did not get a good "hot" connection when I re-soldered. Rolling Eyes I don't think I could win a soldering competition! I never thought about the diode Pleat....Thanks. If that is not it I will apply heat as Steve suggested. In the meantime I will pull another 200 from the pile and try it. Thanks guys, and MERRY CHRISTMAS!

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