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[guitarbth]

Hi all,
Recently I have been having some trouble with my power amp. It's a Crown DC-300A pushing some NS-10s. Well, just all of a sudden the amp would constatly be clipping, creating a distorted sound from the speakers. At first, it would do that for a few seconds and then stop. Now, it doesnt seem to stop. I, of course, don't let it sit and continue to do that for too long as I want to keep my speakers in good shape. I never had it up too loud so my speaks havent been damaged. Channel 2 is especially bad as its clip indicator lights up more than Channel 1 but they're both doing it a lot. I cracked her open to see if there was anything obvious that may be affecting the issue and didnt see anything. What may be the problem here and how can I go about fixing it. Any info would be greatly appreciated.

Brandon

[Brian Roth]

DC-300 and D150 amps had a voltage doubler supply that fed the output driver stages, and the caps go bad.

Bri

[guitarbth]

So is this a common result of the caps going bad? Are those the big caps on the back of the amp? Can they be replaced? Again, your help and any info you can share would be greatly appreciated. Thanks.

Brandon

[Sahib]

I'll amend my post. I'll check the power supply first if there is something that is limiting the supply voltage. So Brian may have got his finger on it first time by asking you to check the caps.

Cemal

[David Kulka]

Boy, I used to work on those amps all the time.  Being direct coupled (that's where the DC in the model number came from), that amp doesn't have very many caps; none in the audio signal path.  If you have the same problem on both channels, I think you should follow Brian's advice and check the bias circuit.  Specifically, the caps there that usually went bad were C4; 10 uf @ 150v, C5; 10 uf @ 50v, and C1; 100 uf @ 12v.  The diodes and transistors in that little part of the circuit would sometimes fail as well.

If the problem just happens on one side that's a different story, and it will probably be a bit tricker to repair.