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Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 12:43 pm
by Guy
Yup, if you don't know how to use a voltmeter, it's time to take it to someone else for some electron tracking. If David is up for it, that's be good because he's close (I think). (Don't you love it when someone volunteers you?!) :angry-tappingfoot:

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 12:56 pm
by craigh
David did look at it. I did as he suggested & I replaced surge voltage capacitor, rectifier tube & fuse. All tubes properly glow but no sound.

Craig

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 1:48 pm
by randy warren
did David get it working at his house? When was the last time it made sound? And by sound, do you mean NOTHING? No hum, noise, anything?

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 2:02 pm
by craigh
David figured out there was a short. We never hook it up for music due to that. It worked till it shorted out roughly six years ago. Today no sound, no noise & no hum. Just the beauty of the light tubes.

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 2:30 pm
by Guy
It looks like there is more than one problem, so it would be good if David can take another look at it. It may seem frustrating, but I bet there's not much more wrong with it. The short may have taken something else with it, or something is just a bit too old. I'm sure it will work again! :thumbup:

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 2:51 pm
by Roscoe Primrose
Guy wrote:just a bit too old. I'm sure it will work again! :thumbup:


Guy uses that line a lot :lolno:

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 4:59 pm
by craigh
I'm just a bit too old. LOL

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 6:42 pm
by dberning
Yes, we had it working here with the 5U4. The filter capacitor was bad in addition to the shorted rectifier tube which blew the fuse. We had it working, but there was very high ripple in the power supply, but the amp put out good power in both channels. I suspect that you are missing a B+ connection when you installed the filter capacitor. There are a lot of chances to do this as it is a multi-section capacitor. A multi-meter would help track down the problem, and I would be happy to take another look to see what's wrong.

David

Re: My dead Dynaco ST-70

Posted: September 17th, 2013, 8:49 pm
by craigh
I would appreciate that. When is good for you?

Craig

Re: My dead Dynaco ST-70

Posted: September 20th, 2013, 11:24 am
by craigh
The ST-70 is up & running. Doesn't have the "slam" of the SS amp I was using but it's so much better. Thank you for everything David.

Craig