marshall 5210 help

[pontiacpete]

Hi, This amp is not getting the + voltage on ZD2. The filter caps are reading a +/- voltage. ZD1 has the -15v, but nothing on the other. This looks like a BZY880 or BZY88X 15v zener. I can't find any data sheets for either and was wondering if I could use a 1w 15v zener like a 1N4744a.
Can anyone help here?
thanks, pete

[52 Bill]

If there is 0 volts on ZD2, either there is a short somewhere in the amp like ZD2 as you suggest or R36 is open. Is R36 getting hot? Does ZD2 test as a short?

[pontiacpete]

ZD2 does not measure as a short. R36 is not open, 2.2K. It looks like on the schematic it's 220R, no? But it has red red red bands.
And it's not getting hot.

[Gtr_tech]

The zener regs run off the main rails. Do you have both rails present and of correct voltage at the output devices? If the 220r is ok, then sounds like yer missing one of the rails due to an open diode in the bridge.

[pontiacpete]

I have +/-27 on the main filter caps.

The collectors on the mj2500 /3000 have +/-27. No DC pins.

[Gtr_tech]

Check for bad traces with a meter set on continuity beep. You could have a broken trace or pad that you can't see, but the meter will find it.

[pontiacpete]

Thanks for the help Gtr and 52, it was the 220r afterall, R38, I thought it said R36 and was testing the wrong one(not a great copy of the schematic, I guess). Anyway, R38 had gone up in value to about 95K.

Thanks again, pete