Another Egnater issue

[Helmholtz]

The scope picture shows only one rectified half-wave peak per cycle, meaning half-wave instead of full.wave rectification.
The only explanation for this is that only one of the diodes is operative (as you confirmed earlier that both sections of the HV winding work).
C127 has nothing to do with that.
As diodes rarely go open, I suspect the connections/solder joints.

[g1]

I think at this point you should just replace the diodes (or the one that was not replaced?). And have a meter on that cap when you power it up. It will probably be close enough (or over) to 400V that you will want to replace it with the proper 450V type anyway.

[Randall]

I will replace the diodes, but riddle me this... With QC104 and 105 disconnected from the PT, D101 tests good (0.5v) from QC104 to the left side of the standby switch. D102 tets good from QC105 to the left side of R116. Doesn't this show both diodes and their connections are good?

[The Dude]

What about the transformer or transformer connection itself? Bad spade lug, open winding, etc. Check the transformer itself (outside to outside winding) for ACV. Or while it's hooked up, check ACV at the two diode anodes to see that full AC is getting all the way to the anodes.

[Dave H]

I don't think it's half wave rectified. The peak frequency is 120Hz and the peak amplitude is only 120V which can't be right with 305V rms input. I'm guessing C127 is disconnected and the trace 'flat' section is being propped up via the 1k resistor from the following capacitor. Randall set your scope to DC coupling and measure the voltage of the 'flat'. Double check all connections/solder joints/traces to C127. There must be a break somewhere.

Edit:
Could you temporarily tack a 100u cap between the cathode of one of the diodes and QC107 to see if that fixes it?

[Helmholtz]

I don't think it's half wave rectified. The peak frequency is 120Hz and the peak amplitude is only 120V which can't be right with 305V rms input. I'm guessing C127 is disconnected and the trace 'flat' section is being propped up via the 1k resistor from the following capacitor. Randall set your scope to DC coupling and measure the voltage of the 'flat'. Double check all connections/solder joints/traces to C127. There must be a break somewhere.

Ouch, you're right, my bad.

Seems I'm making too many mistakes when I post late at night.

[Randall]

Tacking in the 100uF cap seems to have corrected the problem. I am going to lift the board again and see what's up, and report back.

[g1]

If it is double sided board, and there are top side and bottom side traces connected to same cap terminal, check that they are connected.
And let us know what the B+ ends up being.

[Randall]

Dave H, you were partially right, as was g1. It was a connection on C127. Turns out the replacement I installed has snap in leads, and I drilled out the holes just a bit to make it fit. By doing this, I removed the thru board plating. The cap got it's + connection from under the board, and the negative from the top of the board. So it wasn't getting it's negative connection. I ran a wire from it to QC107, the PT CT, and now everything is fine. It biased up nice, and the B+ is now 388v. I put the original 450v back in, I didn't measure any leakage at 350vdc.

As always thank you so very much for your helpful ideas and knowledge. This one is outta here!

[glebert]

An Egnater with power supply problem that isn't a bad PT! Hooray!