02-22-2018, 02:45 PM
Hello Mitch,
Assuming one side is indeed fine, there are several ways to approach this:
-One issue that will offset the bias voltage is a bad ".33" cap C11/C13. A shorted or leaky cap will cause a connection between the higher voltage positive DC on the plate side of the Phase Inverter with the negative voltage on the grid supply of the power tubes. Lifting the leg on the power tube side of the ".33" and measuring the DC on both sides of the cap with the amp on will tell you if it's passing voltage or blocking it as it should. Use caution and turn the amp off and and unplug it while unsoldering/resoldering the legs. You don't need the power tubes in the amp for this test.
-With the amp off and unplugged, ohm out all bias supply resistors and connections (wires and traces) post diode. Measuring resistors in circuit may yield inaccurate readings, but having a supposedly "good" side should help to compare one side to the other. The proper way of course would be to unsolder one leg of each resistor and lift that leg up and measure the resistor directly. I've seen plenty of V-4 PCB's that will have the solder pad or trace blown due to minor soldering. These can go from obvious to hairline breaks, so be very observant.
-Observe the voltages with no power tubes in the sockets. They should all be relatively the same. If they are not, start tracing the voltage back on the sockets that are wrong until you find where the discrepancy starts. Make sure you measure the pins from the tube side of the socket as well (although I do not think you have a pin issue, it's always nice to know for sure).
-Double check your original work! The one thing both of these amps have in common, frankly, is you. Make sure you didn't cut any corners or try to make or unmake connections you found not to your liking. This could be an easy case of accidentally introducing the problem. Was this an issue before you rebuilt the outputs?
Attempt a few of these troubleshooting tests/observations and let us know how you make out. Always be careful and use extreme caution!
Assuming one side is indeed fine, there are several ways to approach this:
-One issue that will offset the bias voltage is a bad ".33" cap C11/C13. A shorted or leaky cap will cause a connection between the higher voltage positive DC on the plate side of the Phase Inverter with the negative voltage on the grid supply of the power tubes. Lifting the leg on the power tube side of the ".33" and measuring the DC on both sides of the cap with the amp on will tell you if it's passing voltage or blocking it as it should. Use caution and turn the amp off and and unplug it while unsoldering/resoldering the legs. You don't need the power tubes in the amp for this test.
-With the amp off and unplugged, ohm out all bias supply resistors and connections (wires and traces) post diode. Measuring resistors in circuit may yield inaccurate readings, but having a supposedly "good" side should help to compare one side to the other. The proper way of course would be to unsolder one leg of each resistor and lift that leg up and measure the resistor directly. I've seen plenty of V-4 PCB's that will have the solder pad or trace blown due to minor soldering. These can go from obvious to hairline breaks, so be very observant.
-Observe the voltages with no power tubes in the sockets. They should all be relatively the same. If they are not, start tracing the voltage back on the sockets that are wrong until you find where the discrepancy starts. Make sure you measure the pins from the tube side of the socket as well (although I do not think you have a pin issue, it's always nice to know for sure).
-Double check your original work! The one thing both of these amps have in common, frankly, is you. Make sure you didn't cut any corners or try to make or unmake connections you found not to your liking. This could be an easy case of accidentally introducing the problem. Was this an issue before you rebuilt the outputs?
Attempt a few of these troubleshooting tests/observations and let us know how you make out. Always be careful and use extreme caution!