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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 12:43 pm 
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Joined: March 5th, 2013, 9:35 am
Posts: 259
Location: Highland, MD
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:

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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 12:56 pm 
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Joined: July 27th, 2013, 7:30 pm
Posts: 27
Location: Germantown, MD
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


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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 1:48 pm 
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Joined: March 12th, 2013, 1:49 pm
Posts: 214
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?


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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 2:02 pm 
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Joined: July 27th, 2013, 7:30 pm
Posts: 27
Location: Germantown, MD
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.


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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 2:30 pm 
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Joined: March 5th, 2013, 9:35 am
Posts: 259
Location: Highland, MD
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:

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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 2:51 pm 
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Joined: February 28th, 2013, 10:38 am
Posts: 1682
Guy wrote:
just a bit too old. I'm sure it will work again! :thumbup:


Guy uses that line a lot :lolno:

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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 4:59 pm 
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Joined: July 27th, 2013, 7:30 pm
Posts: 27
Location: Germantown, MD
I'm just a bit too old. LOL


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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 6:42 pm 
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Joined: March 2nd, 2013, 2:43 pm
Posts: 216
Location: Potomac, MD
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


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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 17th, 2013, 8:49 pm 
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Joined: July 27th, 2013, 7:30 pm
Posts: 27
Location: Germantown, MD
I would appreciate that. When is good for you?

Craig


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 Post subject: Re: My dead Dynaco ST-70
PostPosted: September 20th, 2013, 11:24 am 
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Joined: July 27th, 2013, 7:30 pm
Posts: 27
Location: Germantown, MD
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


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