ST-70 Rectifier problem?

Dynaco-Doctor Forum

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OK, here's the scenario: I decide to fire up one of my Stereo 70's that, admittedly, I havenâ€™t used in a few months. (It was working fine when last used.) After hook up I power it up, everything looks normal. Music starts playing but I notice a slight glow on the rectifier plate which is getting worse. While going for the power switch, I hear a gentle thump, a flash in the rectifier tube and no music. The fuse did not blow, at least not before I got to the power switch. Hmm, I think, blown rectifier tube perhaps. I replace the tube with another inexpensive Sovtek and try again. Same thing, but it took a bit longer to happen. I havenâ€™t tested the rectifier tubes yet to see if any damage was done to them.
I've been intending on completely rebuilding this Stereo 70 but I'd sure like to know what's wrong before I start tearing it down. I've got a feeling it's got something to do with the fact that it sat unused for a while. The quad cap is not that old, 3-4 years perhaps. I donâ€™t own a Variac so I decided to try it, in light of the planned rebuild.
Any ideas?

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Topic - ST-70 Rectifier problem? - Marshall W 08:55:49 02/4/06 (1)

Re: ST-70 Rectifier problem? - Joe Curcio 07:16:01 02/7/06 (0)

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