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ampage archive
Vintage threads from the first ten years
Blues Deluxe Fried It's PT
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 10/3/2005 11:31 AM |
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Jack Collins |
Blues Deluxe Fried It's PT Flipped the switch on my Blues Deluxe the other day and nothing happened. No pilot light or tube heaters light up. Fuse not blow. Opened it up and checked secondary voltages...nada. I found that that primary was open. Pulled the PT and took off the bell covers. I can seen where one of the laminations is burned. I'll order a new one. When I install, I'll use my light bulb limiter to protect from high current draw. Question, is there anything I should be checking for? Could some other kind of component failure have caused the PT to blow w/o blowing the mains fuse? |
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| 10/3/2005 7:04 PM |
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| paulh |
Connections on the bias filter caps. I've seen more than one of these do this. It causes the bias voltage to dip to about -20 volts slowly cooking the tubes and pwr tranny. The main fuse will usually not blow and the amp will work but will sound a little under pwr'ed. |
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| 10/4/2005 11:09 PM |
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| Don Symes |
The joints fail open? Like the cement dropping resistors in the +/-16V supply? That's annoying ... design defects are ... what do you suppose the odds are of convincing Fender to replace the PT under warranty - or at least cough up a free one for your labor? | |
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| 10/6/2005 9:38 AM |
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| R.G. | Wow! That's a strange failure mechanism. I'm always thinking about how to prevent failures and to diagnose them non-destructively. I wonder if it's common enough to put in a turner-offer that will not let the B+ come on if there is not more than (justpick a value out of thin air) -30V on the bias supply. Or a thermal cutout on the power transformer, perhaps. |
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