Power Supply Test

[oguinn]

Alright, got past the first power supply test. Voltage was 6.2 VDC. Now on to the 275 VDC test, and I’m getting a slow climbing reading in the mV range. I turned it off after a minute and it was at 670 mV. I’m thinking it might be that I’ve missed the pads with the alligator clips. The reason I think that is because I had something similar on the 6V pad and readjusted and it worked. I’ve tried twice with the 275 pad.

Is it possible to use probes for this test? Or would that be super dangerous given how long the power supply stays energized?

[Paul Birkeland]

I would use probes.

You can improve the performance of test leads by soldering the ends.

[oguinn]

Ok. Probed it. Same situation. I assume it should read 300-500 VDC pretty immediately, right? I’ll post some pictures in a few minutes once the power supply has de-energized.

[oguinn]

Here’s an album of the power supply. Are there any glaring errors? Anything to try out? https://imgur.com/a/wYmhnmy

[Tom-s]

It's not that the HV is rectified with the Schottky diodes and the heaters with the other diodes?
As i'm missing the shottky's on the board?

Don't have a Eros, don't know what the supply looks like. 

Because this could explain the problem and the voltages you get.

Edit;' and what the board looks like (underneath).

[oguinn]

God I’m dumb. That’s it. Thanks for that. Good eye.

[Tom-s]

The 135Vac should double-up, but it needs some direction to do so  . 

[oguinn]

That fixed it. I feel very dumb.

[Tom-s]

You've learned from this how your PS works and that your HV has a working CRC filter 

[grufti]

While you're at it you might want to chop the short section wire that's sticking out at T12. It looks like it is long enough to contact T11 accidentally, if it is ever bent over that way.

[Paul Birkeland]

The 270K resistors should rest against the board too.

[Deke609]

The 270K resistors should rest against the board too.

@PB - Just curious: why do they need to be against the board? I assume that they are bleeders for the HV power supply caps, and so don't need to be raised from the board b/c they don't dissipate much if any heat. But why is it a bad idea to have them raised?  Does the extra lead length risk picking up noise?

many thanks, Derek

[Paul Birkeland]

If they can move around, it becomes difficult to predict what they might touch that they shouldn't.  If they are up off the board, it's more likely that they will break loose, and if one resistor breaks loose and the other does not, that will cause some problems with the DC voltage balance across those power supply caps.

[Deke609]

Many thanks PB. Makes sense.

[oguinn]

Thanks, everyone. I’ve shared that all up and made it past the shunt regulator tests. Waiting for the power supply to de-energize, then onto the audio circuit