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leo1254 3rd July 2009 11:42 PM

dynaco system- volume remains
My Dynaco st-70 is connected to a Dyna PAS. Because of a failure event (quad cap)I recently replaced most of the capacitors and the choke in the amplifier. All replaced parts were of the same value.

Now the amp seems louder, and with volume turned off, music is still audible. (Its very low but I can hear it).

I have an mp3 player with the volume set at 10 (25 max) connected to the "spare" outlet of the PAS.

Any Ideas?

vconsumer 4th July 2009 05:55 PM

How long do you continue to hear music after you power down the amp?

leo1254 4th July 2009 11:44 PM

volume remains
Hi V,
Thanks for the reply. I am not a tech.

In the Amp:
This st-70 system blew the quad cap, the rectifier tube arced, and the fuse blew. Since, I have replaced the quad cap, and all (caps) but the double capacitor on in the terminal strip (bias circuit). The choke is also new.

In the process of doing this work, I managed to break off the leads to two 2w resistors. (1= 6.8kohms 2=10kohms) one was attached to the quad cap, and the other the terminal strip. New ones are on order, but currently, I just used a piece of wire to repair the ones that broke.

In operation, it has a very sensitive volume control. I barely can turn it a hair before it is too loud. When I turn the knob off, I can hear music. I have an mp3 player with volume on 5 (possible 25) patched in to the "special" location on the back of the dyna pas.
Increasing volume, with or without sound=distortions noise and clipping.

In the pas:
I used deoxit on the big switch no one likes, (no repairs). The sound stops when the switch is opened, and then I hear a short fuzzy sound like wrinkling paper.


leo1254 6th July 2009 02:04 PM

volume remains
I in the first post I said I was connected into "spare" of the Dyna Pas.I was in error. I am in the "special" jack.

Also, when system is turned off, I do not hear music, it is quiet right away, followed by a crackle.

llwhtt 6th July 2009 02:58 PM

That explains everything, the "special" input is a phono or low level input NOT a high level input. That's why it's louder and probably doesn't sound right either since it is EQ'd for phono use. Use the "spare" input and all should be back to normal. What were you using before?


leo1254 8th July 2009 12:56 AM

volume remains
Thanks Craig!

That resolved the problem, Is there any chance I damaged anything?

llwhtt 8th July 2009 01:12 AM

Probably not, that's what's cool about tubes. You can screw up, within reason, and not the let the smoke out! Though nothing would have happened if it were solid state either, in this case.
Go to Dynaco Doctor and down both manuals if you don't already have them. If you DO have them, read them, haha.


llwhtt 8th July 2009 01:14 AM

Don't down them, download them, oops.


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