Marshall JCM2000 DSL100 High Current Draw

[Delta362]

Not seeing any attachment.

Thank you

Able to see the attached file this time?

[misterc57]

Able to see the attached file this time?

No. After "Upload Attachments", are you clicking "insert" for a pdf or a size like "medium" for an image?

Anyway, I think I understand the test you described. I disconnected all primary cables from the board. So I am bypassing all cables, switches, etc. in the amp.

I directly connected mains hot/neutral to red/blue. High current draw at just 3 VAC
I directly connected mains hot/neutral to red/brown. High current draw at just 3 VAC

[Delta362]

PT windings.pdf

[Delta362]

I hadn't done the Insert before. For all other posts with attachments that I've done, I just clicked upload attachments then post reply.

[Delta362]

Since you have high current draw for each pair individually, I'd say your PT is shot and will need to be replaced.

[misterc57]

Seeing the image now. My last test I had not connected per your diagram.

I will test again in the morning.

Thank you

[misterc57]

If I understand correctly now. W9 (brown) and W1 (red) is one winding. W2 (blue) and W6 (red) is one winding. If I connect my mains to each individual winding, I am NOT seeing any current draw.

W9 to W1 resistance is open

W2 to W6 resistance is open

My prior readings and testing was done at W9 to W6 and at W2 to W1.

[Delta362]

W9 and W6 are physically connected via a trace on the board. You'll read a short with nothing connected. Same thing with W1 and W2 being physically connected via a trace on the board.

For the PT, take the blue lead and find out which red lead gives you a small ~2 ohm resistance. Connect the blue wire to W2, and connect that matching red wire to W6. Now apply power to the mains inlet with your variac. Any heavy current draw? No? It's good, then.

Next take the brown lead and remaining red lead (that gives you about ~2 ohm resistance between those two). Connect the brown to W9, and connect the remaining red to W1. Now apply power to the mains inlet with your variac. Any heavy current draw? No? That's good, too.

At this point, you'll have both of your primary windings (A red/blue pair, and a red/brown pair) connected to the power supply board correctly. Power it on thru the mains inlet again. There should be no heavy current draw. If that's all good, then you're ready start to connect your secondary windings.

[Delta362]

I think part of the confusion on the schematic for you might be the dotted lines for the red leads. They are showing that you'll either connect two sets of windings in parallel (like you're ultimately doing for 115V), or two windings in series thru W4 and W5 if you're supplying a 230V.

[misterc57]

Sorry, I am adding confusion. When I reference W9, W1, W2, W6 below, I am referring to where they connect at the PT primary. The wires are not connected and I am taking readings at the PT primary taps.

So the board connections or traces are not a factor in these readings.

If I understand correctly now. W9 (brown) and W1 (red) is one winding. W2 (blue) and W6 (red) is one winding. If I connect my mains to each individual winding, I am NOT seeing any current draw.

W9 to W1 resistance is open

W2 to W6 resistance is open

My prior readings and testing was done at W9 to W6 and at W2 to W1.

[Delta362]

Please connect the brown wire to W9 on the board and the corresponding red wire to W1 on the board. Then power up to check current draw. This will test both the board and one of the PT windings in the circuit.

If it's low current, then power off. Connect the blue wire to W2 on the board and its corresponding red wire to W6 on the board. Then power up and check current draw.

[misterc57]

Please connect the brown wire to W9 on the board and the corresponding red wire to W1 on the board. Then power up to check current draw. This will test both the board and one of the PT windings in the circuit.

If it's low current, then power off. Connect the blue wire to W2 on the board and its corresponding red wire to W6 on the board. Then power up and check current draw.

W2 and W6 were okay.

W9 and W1 caused high current draw.

Could there be anything besides the PT primary causing this?

[Delta362]

Remove the blue/red pair wires from W2 and W6 leaving the W9 brown and W1 red pair still connected to the board. Does that draw high current? If so, your PT is toast.

[Delta362]

You still have all the secondary wires removed during all of these tests, correct?

[misterc57]

You still have all the secondary wires removed during all of these tests, correct?

Yes