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Hi,I was hoping I might be able to gain a little guidance from yall. I have a ST70 which I am trying to install a Curcio upgrade driver board and capacitor upgrade module on. I installed the driver board first and everything worked perfectly afterwards.
I then installed the quad cap board and the amp has not worked since. When I turn the amp on with the bias pots turned all the way down, the bias gradually rises to around .5 and holds strong for about a minute. Then out of nowhere the bias shoots up to well over 1 and one or two of the driver tubes begin to flash blue. I have rechecked all the connections and wiring and have been able to find nothing wrong. I really hope yall can help me because I am at a loss. Thanks.
Follow Ups:
Phillip me an email at merccougar89@yahoo.com and I can walk you thru the troubleshoot procedure on those..Your email isnt open on the AA.
Mike
Really you should take this post to the dynaco forum.I'd say you proable have a poor solder joint/connection on the bias circuit in the cap board. You can pull the tubes and measure the negative voltage on the el34 sockets.
Poor connections between the el34's and the tube sockets are likey as well as a wonky bias pot. Coupling caps leaking can also cause this. But I'd look at the bias circuit on the cap board first. Make darn sure the diode and caps are installed for proper polarity. Also make sure the caps aren't touching anything as thier outer case is "live".
Thanks for the help. I thought that it might be the bias pots, so I just replaced them today and the bias is still way too high. The coupling caps are also brand new and installed a few day ago with the new driver board, but you never know. I know the polarity is right as I have looked over it several times. All the solder joints look good, but I will go ahead and redo them again just to be sure.I had no idea about the skin of the caps being live...that could be the problem since several of the caps are touching the chasis and probably each other. Could that ruin the caps, or can I just seperat all the caps and they should be good?
Thanks for the help. I thought that it might be the bias pots, so I just replaced them today and the bias is still way too high. The coupling caps are also brand new and installed a few day ago with the new driver board, but you never know. I know the polarity is right as I have looked over it several times. All the solder joints look good, but I will go ahead and redo them again just to be sure.I had no idea about the skin of the caps being live...that could be the problem since several of the caps are touching the chasis and probably each other. Could that ruin the caps, or can I just seperat all the caps and they should be good?
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