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#1
08-15-2015, 12:30 PM
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B&k 747 tube tester died
My B&K 747 Tube tester just died in the middle of a restoration. I was testing a 12SN7. The first section tested perfectly and I had just changed the settings to the second section when the tester gave no result. Moving back to the first section I also got no result. Replacing the tube under test with a good 6K6 I also got no result. Checking tube voltages, I found Fil B+ and screen voltages on the 6K6 were correct but there was a negative 54 volts on the grid even with the test switch no pushed. Pushing the switch resulted in a negative 60 volts on the switch. Clearly a component on the PC board attached to the meter died. My question is ..Should I get the replacement board being offered or should I simply troubleshoot the old board. I was planning to replace the board at some time in the future because the new board looks great. Comments?????
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#2
08-15-2015, 03:37 PM
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My B&K 707 died after being in storage for several years, I replaced the only electrolytic in the thing and it came back to life.
Not sure if this will apply to the 747 at all but thought I'd toss it out there.
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#3
08-16-2015, 01:39 PM
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there is a resistor on the end of the switches that opens up. Its part of a voltage divider. IIRC its a 470ohm 7 watt R-27. Very common prob on 747
the neg voltage with nothing pushed is correct, the -60 with the button pushed mean that resistor has opened. Last edited by DaveWM; 08-16-2015 at 04:10 PM.
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Linear Mode
