Egnator 40

[Helmholtz]

I'm not sure what you mean by "other two PT secondaries". There are 5 pairs (same color). Are you saying to pull each pair one at a time to see whether the current rises. If so, do I pull each pair and if it doesnt rise, plug them back in & move on to the next pair?

The schematic in post#25 shows 3 separate PT secondary windings: red-red (high voltage supply), brown-brown (low voltage and bias supply) and green-green (heater supply). As there seems to be no problem with the high voltage supply (red-red), disconnect at least one of the brown wires and watch mains current and if no change re-connect and disconnect at least one of the green wires.

Edit: Please ignore as schematic in post #25 is for a different amp.

[Perkinsman]

There are 4 pairs of secondary wires, not 3 or 5 as previously reported. I'm not sure post #25 is the same PT. I'm attaching the Egnator 40 PT schematic again. When I detach the red wires (I called them pink before) the current stopped rising. This pair has 680vac, 117ohm, but no continuity. Does this help narrow down the problem?

[Helmholtz]

There are 4 pairs of secondary wires, not 3 or 5 as previously reported. When I detach the red wires (I called them pink before) the current stopped rising. This pair has 680vac, 117ohm, but no continuity. Does this help narrow down the problem?

Sorry, I can only go by the info provided. BTW, 117R means continuity.
Please verify the wiring that connects to the red-red winding shown in post #25. You may want to disconnect C51 for a test.

[Perkinsman]

Here's a pic of the transformer I/O diagram from your pdf. It looks like you have all of the right voltages on all 4 taps. Not sure what the red is? Also, the fact that it powered up and didn't blow a fuse with secondaries unhooked indicates that the transformer is likely good. See my post #19.

[ATTACH=CONFIG]57174[/ATTACH]

My error, I thought there was a red pair from the PT but they were just inside the same wiring harness. You are correct, there are 4 pairs along with a black & grey wire (I assume the center taps)

[Mick Bailey]

You're confusing continuity and resistance. No continuity is open-circuit, or infinite resistance. Continuity is where there's an electrical path, an expected resistance, or some other resistance, but the circuit is not open.

Maybe the confusion arises because some DMMs have a continuity setting that buzzes or beeps below a preset resistance, maybe 10 ohms or whatever, and doesn't beep over this threshold. This is useful for checking circuits where the expected resistance is low, such as connections to ground, cable connections, or automotive wiring etc. It's no good for measuring or checking connections where the expected resistance is higher than the threshold, as in the case of HT windings.

Your problem lies with the circuit and not the transformer. Check the position of the standby switch - does it fully isolate the HT? Is the switch actually working - does it break contact?

[Helmholtz]

...and check if the suspicious (0.1µF ?) ceramic disk is actually connected after or rather before the standby switch and if disconnecting it solves the problem.

[Perkinsman]

Thanks for that Mick, you're correct in that I assumed that my Fluke beeped anytime there was continuity, I didn't realize there is a threshold. How do I test the standby switch for the things you menntioned? Does it matter that the current rises despite the position of the switch?

[Perkinsman]

I don’t have a c51 on the board. In the area that was circled earlier, I have a c41, c42, c49 & c50.

[Helmholtz]

I don’t have a c51 on the board. In the area that was circled earlier, I have a c41, c42, c49 & c50.

Ok, then please post pictures of the board area concerned.

[g1]

I don’t have a c51 on the board. In the area that was circled earlier, I have a c41, c42, c49 & c50.

The schematic shown in post #25 is a Fender schematic. It illustrates only where the cap is located in an electronic sense. The component number designations will not correspond to the Egnator in any way.

The photo in post #25 should be correct.

[Perkinsman]

Ok, then please post pictures of the board area concerned.

First pic is of the 4 ceramic caps...I think they're all .1uf's. There's also a larger blue ceramic cap, is that a thermister? The 2nd pic is of the 2 red wires from the OT. Once detached the entrance fuse and mains fuse hold, the amp lights up, the filaments on all tubes are lit but of course no high voltages or sound.

[g1]

The blue cap next to the fuse is in the same position as the one that was pointed out as a suspect in post #25.

[Perkinsman]

Is that blue disc a cap or a thermister? I can see two small black spots (holes maybe?) on it. Would that be an indication of it burning out?

[Perkinsman]

Is that blue disc a cap or a thermister? I can see two small black spots (holes maybe?) on it. Would that be an indication of it burning out?

Here's pic thru my magnifier.

[Mick Bailey]

It looks like a resin-dipped cap and the one that's been mentioned. Clip it out for now and see what happens - the circuit will be fine without it for testing. A thermistor is in series with a supply and if shorted the circuit still works, if open it doesn't, but it in either case would not cause excess current draw.

A MOV can look similar (or the same) and fail in the same way. You should be able to read a value whatever it is.