I thought this attachment might be helpful.
U3 and U6 anodes are tied to the -35v rail. The TL431's set the bias on the base of their respective Q5,Q23-MMBT2484. Which are part of the Long tail constant current source for the differential amps. I'm not sure what the voltage will be, but will be a positive voltage much less than 35 volts.
The Test Points can be used with black probe on non bridged speaker terminals which happen to be signal ground as pictured. Be very careful when probing tests points. The voltages are printed on the silk screen. TP chassis and ground should not have any significant voltage. If they do the thermal pads may be perforated. TP U2-6 and U5-6 should not have more than a volt, if they do they may be damaged. Test voltages with no signal applied.
U3 and U6 anodes are tied to the -35v rail. The TL431's set the bias on the base of their respective Q5,Q23-MMBT2484. Which are part of the Long tail constant current source for the differential amps. I'm not sure what the voltage will be, but will be a positive voltage much less than 35 volts.
The Test Points can be used with black probe on non bridged speaker terminals which happen to be signal ground as pictured. Be very careful when probing tests points. The voltages are printed on the silk screen. TP chassis and ground should not have any significant voltage. If they do the thermal pads may be perforated. TP U2-6 and U5-6 should not have more than a volt, if they do they may be damaged. Test voltages with no signal applied.
Attachments
I just received a ZR360 as it happens, and the following are the measurements for U3 and U6.Using Q18-center leg (-35 volt rail) for the black probe.
Pin 1- 2.5 volts
Pin 2- 0 volts
Pin 3- 0 volts
Pin 4- NC
Pin 5- NC
Pin 6- 0 volts
Pin 7- 0 volts
Pin 8- 2.5 volts
Pin 1- 2.5 volts
Pin 2- 0 volts
Pin 3- 0 volts
Pin 4- NC
Pin 5- NC
Pin 6- 0 volts
Pin 7- 0 volts
Pin 8- 2.5 volts
Gents thanks for assistance.
I had to push this aside and luckily, I found I had a faulty probe on the very next amplifier, Perry is right as usual, please disregard measurements in post #15.
The measurements as PapaZbill outlined, were on point:
Post #21:
All voltages on the test points checked out as per the silk screen.
I had the amplifier disconnected this morning and returned, powered up (first power up after being disconnected for some time) TP U2-6 and U5-6 had 14v which quickly went to 0v when powered up. Power ups after this didn’t repeat this finding. I’ve left the amplifier disconnected to try again tonight or tomorrow.
Post# 22:
U3 and U6.Using Q18-center leg (-35 volt rail) for the black probe:
Both U3 and U6 had approximately the same measurements.
Pin 1- 2.493 volts
Pin 2- 8mv
Pin 3- 2mv
Pin 4- NC
Pin 5- NC
Pin 6- 11mv
Pin 7- 2mv
Pin 8- 2.491 volts
After this initial DC at the speaker terminals, the amplifier passes clean audio, and doesn’t repeat until left disconnected for a lengthy period of time.
Thanks again.
I had to push this aside and luckily, I found I had a faulty probe on the very next amplifier, Perry is right as usual, please disregard measurements in post #15.
The measurements as PapaZbill outlined, were on point:
Post #21:
All voltages on the test points checked out as per the silk screen.
I had the amplifier disconnected this morning and returned, powered up (first power up after being disconnected for some time) TP U2-6 and U5-6 had 14v which quickly went to 0v when powered up. Power ups after this didn’t repeat this finding. I’ve left the amplifier disconnected to try again tonight or tomorrow.
Post# 22:
U3 and U6.Using Q18-center leg (-35 volt rail) for the black probe:
Both U3 and U6 had approximately the same measurements.
Pin 1- 2.493 volts
Pin 2- 8mv
Pin 3- 2mv
Pin 4- NC
Pin 5- NC
Pin 6- 11mv
Pin 7- 2mv
Pin 8- 2.491 volts
After this initial DC at the speaker terminals, the amplifier passes clean audio, and doesn’t repeat until left disconnected for a lengthy period of time.
Thanks again.