SILVERTONE POWER SHIFTR

4/18/2013 9:49:46 PMTROY

HAS ANYONE EVER HAD AN ISSUE WITH A BATTERY ELIMINATOR CAUSING BLOWN RESISTORS IN BATTERY RADIOS? I RECAPPED ALONG WITH A NEW ELECTOLYTIC AS WELL AS ALL NEW RESISTORS IN MY 1940 RCA VICTOR 24BT-2 BATTERY POWERED RADIO. WHEN I BOUGHT THE RADIO, A SILVERTONE POWER SHIFTR WAS IN THE BACK. WHEN I TESTED THE POWER SHIFTR WITH MY METER IT PUT OUT APPROX. 118 VOLTS ON THE B+,B- LINE AND 1.85 VOLTS ON THE A+,A-. WHEN I PLUGGED MY RADIO INTO IT, IT DID NOT POWER UP. WHEN I MEASURES THE VOLTAGES AT THE POWER SWITCH, I ONLY HAD 23 VOLTS GOING TO THE SWITCH. I HAD THE CORRECT 1.38 VOLTS ON THE "A" CIRCUITS. I THEN CHECKED ALL MY RESISTORS AND CAPS AGAIN, ONLY TO FIND THE 390 OHM RESISTOR ON THE A- CIRCUIT GOING TO THE 3Q5GT OUTPUT TUBE WAS BURNT UP. I DID NOTICE THAT WHEN I STARTED THE RESTO THAT THIS RESISTOR WAS COMPLETELY BURNT IN HALF. COULD I POSSIBLY HAVE AN ISSUE INSIDE THE POWER SHIFTR CAUSING THE RESISTOR TO BURN UP OR COULD A BAD TUBE CAUSE THIS? I HAVEN'T HAD THE TUBES TESTED YET BUT THEY LOOK TO BE IN GOOD SHAPE. THEY LOOK ALMOST BRAND NEW. THE POWER SHIFTR STILL HAS ALL THE ORIGINAL CAPS IN IT. DO I MAYBE NEED TO RECAP THE SHIFTR AND RECHECK? ANY ADVICE WOULD HELP. THANK YOU.

4/19/2013 3:54:49 PMTom McHenry

:HAS ANYONE EVER HAD AN ISSUE WITH A BATTERY ELIMINATOR CAUSING BLOWN RESISTORS IN BATTERY RADIOS? I RECAPPED ALONG WITH A NEW ELECTOLYTIC AS WELL AS ALL NEW RESISTORS IN MY 1940 RCA VICTOR 24BT-2 BATTERY POWERED RADIO. WHEN I BOUGHT THE RADIO, A SILVERTONE POWER SHIFTR WAS IN THE BACK. WHEN I TESTED THE POWER SHIFTR WITH MY METER IT PUT OUT APPROX. 118 VOLTS ON THE B+,B- LINE AND 1.85 VOLTS ON THE A+,A-. WHEN I PLUGGED MY RADIO INTO IT, IT DID NOT POWER UP. WHEN I MEASURES THE VOLTAGES AT THE POWER SWITCH, I ONLY HAD 23 VOLTS GOING TO THE SWITCH. I HAD THE CORRECT 1.38 VOLTS ON THE "A" CIRCUITS. I THEN CHECKED ALL MY RESISTORS AND CAPS AGAIN, ONLY TO FIND THE 390 OHM RESISTOR ON THE A- CIRCUIT GOING TO THE 3Q5GT OUTPUT TUBE WAS BURNT UP. I DID NOTICE THAT WHEN I STARTED THE RESTO THAT THIS RESISTOR WAS COMPLETELY BURNT IN HALF. COULD I POSSIBLY HAVE AN ISSUE INSIDE THE POWER SHIFTR CAUSING THE RESISTOR TO BURN UP OR COULD A BAD TUBE CAUSE THIS? I HAVEN'T HAD THE TUBES TESTED YET BUT THEY LOOK TO BE IN GOOD SHAPE. THEY LOOK ALMOST BRAND NEW. THE POWER SHIFTR STILL HAS ALL THE ORIGINAL CAPS IN IT. DO I MAYBE NEED TO RECAP THE SHIFTR AND RECHECK? ANY ADVICE WOULD HELP. THANK YOU.
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Something is loading down the B+ bus. The 390 ohm resistor ties the B- side of the supply to ground, so all B current flows through it. This should only be a few dozen mA in a normally-working radio, so the excess current being drawn by the B+ bus is what is burning up this resistor.

You need to examine everything that is hanging on the B+ bus in order to find the source of the load. It might help to first check the B+ bus resistance to ground, then pull all of the tubes and see if it increases. If it does, you have a shorted tube.

This would be my first guess since you appear to have had the same problem (burned out 390 ohm resistor) both before and after you recapped. That suggests that the short wasn't introduced by you as result of the recapping.

I don't think that your battery eliminator is at fault here but a recapping couldn't hurt it. Also, the A supply has an odd "solid state" rectifier which might be worth replacing with a silcon diode (and a series resistor).

4/27/2013 4:29:58 PMRalph Schneider

::HAS ANYONE EVER HAD AN ISSUE WITH A BATTERY ELIMINATOR CAUSING BLOWN RESISTORS IN BATTERY RADIOS? I RECAPPED ALONG WITH A NEW ELECTOLYTIC AS WELL AS ALL NEW RESISTORS IN MY 1940 RCA VICTOR 24BT-2 BATTERY POWERED RADIO. WHEN I BOUGHT THE RADIO, A SILVERTONE POWER SHIFTR WAS IN THE BACK. WHEN I TESTED THE POWER SHIFTR WITH MY METER IT PUT OUT APPROX. 118 VOLTS ON THE B+,B- LINE AND 1.85 VOLTS ON THE A+,A-. WHEN I PLUGGED MY RADIO INTO IT, IT DID NOT POWER UP. WHEN I MEASURES THE VOLTAGES AT THE POWER SWITCH, I ONLY HAD 23 VOLTS GOING TO THE SWITCH. I HAD THE CORRECT 1.38 VOLTS ON THE "A" CIRCUITS. I THEN CHECKED ALL MY RESISTORS AND CAPS AGAIN, ONLY TO FIND THE 390 OHM RESISTOR ON THE A- CIRCUIT GOING TO THE 3Q5GT OUTPUT TUBE WAS BURNT UP. I DID NOTICE THAT WHEN I STARTED THE RESTO THAT THIS RESISTOR WAS COMPLETELY BURNT IN HALF. COULD I POSSIBLY HAVE AN ISSUE INSIDE THE POWER SHIFTR CAUSING THE RESISTOR TO BURN UP OR COULD A BAD TUBE CAUSE THIS? I HAVEN'T HAD THE TUBES TESTED YET BUT THEY LOOK TO BE IN GOOD SHAPE. THEY LOOK ALMOST BRAND NEW. THE POWER SHIFTR STILL HAS ALL THE ORIGINAL CAPS IN IT. DO I MAYBE NEED TO RECAP THE SHIFTR AND RECHECK? ANY ADVICE WOULD HELP. THANK YOU.
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:Something is loading down the B+ bus. The 390 ohm resistor ties the B- side of the supply to ground, so all B current flows through it. This should only be a few dozen mA in a normally-working radio, so the excess current being drawn by the B+ bus is what is burning up this resistor.
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:You need to examine everything that is hanging on the B+ bus in order to find the source of the load. It might help to first check the B+ bus resistance to ground, then pull all of the tubes and see if it increases. If it does, you have a shorted tube.
:
:This would be my first guess since you appear to have had the same problem (burned out 390 ohm resistor) both before and after you recapped. That suggests that the short wasn't introduced by you as result of the recapping.
:
:I don't think that your battery eliminator is at fault here but a recapping couldn't hurt it. Also, the A supply has an odd "solid state" rectifier which might be worth replacing with a silcon diode (and a series resistor).
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I have a power shifter and the first thing I did was recap it, I would recommend this on any old power supply.