Help with dysfunctional MC 240

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I posted a couple weeks ago with a question about my mcintosh 240 that stopped working - blue flash in one of the power tubes, then the tubes lit up but no sound. Any chance of getting some more help from some kind souls?
Last night I checked the voltages and the same thing happened again: blue flash on one of the power tubes, second from left. This was while I was checking it, maybe after about half an hour. I was getting crazy voltage readings on pins 5 and 7 of this tube when it happened. The B+ fuse also blew (as it had the first time). Most of the other voltages aren't too bad. On pin 1 of V2 (12AU7) I'm getting 307v rather than 205v (SAMS), on v5 305v (205v SAMS), on pin 6 of each tube I'm getting 306v and 312v respectively (should be 205v). On pin 2 of V3 and V6 (12BH7) I'm getting 28V rather than 18v (SAMS). So these are all a bit high - I'm not sure how bad this is considered. One inmate suggested I check the thermistor, and that's okay. There are four 56k resistors connected to pin 5 of the 6L6 (the one with the wacky readings) and these are all okay, off by a few ohms but they haven't blown or anything.
I haven't plugged it in since this happened, so I haven't checked the other two power tubes. Thought I'd check in here and see if any Mcintosh fans might have an idea what to check for with fluctuating voltage readings on pins 5 and 7 on one of the power tubes.
Thanks all -
ws

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Parts Connexion

Topic - Help with dysfunctional MC 240 - Will shade 10:04:13 03/27/07 (9)

Re: Help with dysfunctional MC 240 - Michael Samra 21:32:20 03/27/07 (2)

Thanks Mike - Will shade 06:25:52 03/28/07 (1)

Re: Thanks Mike - Michael Samra 16:02:21 03/28/07 (0)

Re: Help with dysfunctional MC 240 - el_37 15:02:36 03/27/07 (3)

Re: Help with dysfunctional MC 240 - Will shade 16:20:29 03/27/07 (2)

Re: Help with dysfunctional MC 240 - el_37 19:08:21 03/27/07 (1)

Re: Help with dysfunctional MC 240 - Will Shade 19:20:22 03/27/07 (0)

Re: Help with dysfunctional MC 240 - Steve O 11:04:23 03/27/07 (1)

Re: Help with dysfunctional MC 240 - Rob Mercure 15:12:20 03/27/07 (0)

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