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Vintage threads from the first ten years

Re: The SVT wins again

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12/1/2005 6:45 PM
R.G.	Re: The SVT wins again keen at "g""e""o""f""e""x"."c""o""m"

12/1/2005 6:01 PM

Well, I hope you put a socket under the IC for future troubleshooting.

R20 & 22 are a couple of 4.7K 2W resistors that feed the bases of Q3 & 4. Make sure they aren't open. My latest guess is that something is not right in the area of (one of) these two transistors. There is a + & - 100V supply that supplies power to the emitters of Q3 & 4 through R14 & 19 respectively. Check the supply voltage and the drop across these two resistors. They should have equal voltage across them. Also check the voltage across R16 & 17. (15K) The voltages here should also be equal, roughly 14VDC. Pulling all the output devicesa and running the amp without a load is a good idea until you find what's causing the imbalance. It's possible you might have a broken/burned trace on the pc board. These problems usually seem pretty simple once you find the cause. Be assured - it will be the last thing you look for.

11/23/2005 3:47 PM
Rick Erickson	Re: Ampeg SVT 3 Pro output has DC Any luck with this one or did you throw in the towel? RE

11/23/2005 11:30 PM
Erik Miller	Thanks for asking, Rick. It's off to one side, awaiting time for me to try your suggestions. I've been down with a miserable head cold since Sunday, so no progress around my one-man shop. Cheers, Erik

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