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Old 13th July 2004, 02:30 AM   #1
rkc7 is offline rkc7  United States
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Default Carvin HT1000 problems

I purchased a used Carvin HT1000 power amplifier from someone for real cheap knowing it had some problems. But the problem is (well, was) strange. When I hooked up a 4 ohm speaker (amp is capable to 2 ohm) to one channel, it worked fine, but when connected to the other my circuit breaker would trip. In bridged mode it worked fine (ch 1 was the offending channel, but I had no problems in bridged). Now, I've decided to upgrade some other parts in it and fixed up a few things I found wrong, but came across something strange. Many resistors throughout the amp are different than the listed value on the parts list, and even some of the resistor areas are listed at "not used" yet have resistors in them. I was wondering if anyone could comment on the channel problem and also any idea why the resistors would be different.

Some examples of resistor differences:

R2 is supposed to be 3.3Kohm, but is 1.5Kohm
R3 is supposed to be 100Kohm, but is 47Kohm
R109 and R209 are "not used" but were 2.2Mohm
R204 is supposed to be 2.2Kohm, but is 1Kohm
R205 is supposed to be 220ohm, but is 100ohm
R212 is supposed to be 470ohm, but is 1.5Kohm

I don't have a schematic or the parts list in file, but you can check the manual for the Carvin DCM1000 which has a parts list and is pretty much identical to the one for mine.

Thanks for any help
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Old 28th July 2004, 01:23 AM   #2
rkc7 is offline rkc7  United States
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Well, no mind to my previous questions. I replaced some of the OPamps that were JRC4558 with NE5332 and replaced the old 5% carbon film resistors (in input and volume control boards, not amp) with 1% metal film (same values as old), fixed an LED for the signal which had a broken leg and put it all back together and now I have a new problem. The amp actually works now, channel one is fine, but now channel two's clip light is always on unless I hook up a speaker, which it will play, but the amp show's it's clipping while playing at anywhere above no sound. There is a noise that seems to be leaking over to channel one as well. When I accidently touched the leads to one of the power transistors, the noise stopped and the clip light went off, and when I touched others it changed the noise. Could this be due to dying transistors or a malfunctioning OPamp I just replaced? When using the diode check on my MM, the voltages were relatively consistent on various arrangements on the transistors, but one channel's were slightly lower than the other. I think it was channel two's which voltage was lower. Thanks for any help.

Ryan
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Old 2nd August 2004, 02:47 AM   #3
rkc7 is offline rkc7  United States
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Aha! Well, I got it to work. I found I forgot to replace a resistor on the amplifier board (doh!). Now it works fine.

One more question... if anyone will have an answer.

When I turn it on SOMETIMES, it blows the circuit breaker in my house. It's a 20A breaker, and there's a 15A breaker on the amp itself, which never blows. I've read a few places about a surge from the transformer when turning it on, but could this mean something is wrong? Other than that, it works fine.

Thanks for any help.
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Old 20th November 2006, 10:27 PM   #4
Thack is offline Thack  United States
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I have a carvin PB500 bass amp where one of the resistors should be 100k but it measures only 47k also.
I think the filter capacitor is sucking all your startup power when you turn it on. It may be damaged or have too much capacity.
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