Old Lafayette combo amp popping fuse... should be simple

[Chuck H]

Is there a pilot lamp in this equation anywhere?

Just trying to figure out what might get arbitrarily hooked up that could cause current draw since the a new diode or new cap or anything seems to cause excess current.

Good troubleshooting so far, but something is missing.?!?

I'm following to see what happens and help if I can.

[Jazz P Bass]

Can a simple drawing be made?
Nobody here knows how you are hooking the secondary up.
How many wires are on the secondary?
For that matter, what Lafayette amp is it?
Is it a tube amp or solid state (what voltages are we dealing with?)

[J M Fahey]

We need that schematic or this discussion is just some hot air.
We don't know how you connected your transformer, your diode, your capacitor.
Words are not precise enough, we need a drawing.
Please label all parts, as D1, C1, etc, plus showing its value.
Wire colors also.

[Jazz P Bass]

If you can correctly identify the secondary wires, this is a good test setup.
If it is center tapped, at first, do not use it.

[J M Fahey]

Dear jazzp.
The idea behind my questions was to have the OP draw what he really has there, and show the mistake he certainly has made.
Now he will point to your drawing and say: "it´s exactly like that one".
Don´t know if what I'm hinting at is clear.

[Enzo]

I kept reading, "when I put a cap across the secondary." Are we putting the filter cap DIRECTLY across a secondary? I saw no mention of rectification in those sentences.

[Jazz P Bass]

Dear jazzp.
The idea behind my questions was to have the OP draw what he really has there, and show the mistake he certainly has made.
Now he will point to your drawing and say: "it´s exactly like that one".
Don´t know if what I'm hinting at is clear.

Yeah, information (or lack of) can be a two edged sword.

[J M Fahey]

Yes, language is an imperfect tool, and more often than not it's not used acurately, because a lot of things are implied, not said.
And not everybody comes out with the same conclusion.
Now that the cat is out of the bag, I suspect *many* possible wrong things.
But rather than offering a 5 or 6 answer multiple choice quiz (which might still leave the real problem untested) I'd much prefer the OP draw the schematic of what he actually sees.
An incomplete list might be:
1) wrong transformer winding.
2) 2X the secondary voltage because a CT secondary was connected end to end
3) reversed diode
4) no diode (Enzo's suggestion, and I think he *also* thought about the others too)
5) reversed capacitor.
6) shorted capacitor
7) shorted diode
8) capacitor rated less voltage than necessary
9) old, half dry, leaky, unformed capacitor
10) twisted together secondaries, which *look* logig ... but are out of phase .... and so on.
I'd prefer to see some drawing made by the OP, before suggesting any solution.

[Chuck H]

Yes, language is an imperfect tool, and more often than not it's not used acurately

What do you mean?

JK

[disorder]

I kept reading, "when I put a cap across the secondary." Are we putting the filter cap DIRECTLY across a secondary? I saw no mention of rectification in those sentences.

Cap is being put AFTER the half-wave rectifier.

Jazz P Bass - my setup is exactly as the picture you have posted, only instead of the resistive load I put the filter cap there. I have tried using both the older stock diode and also a new 1N4007.

The power transformer has no center tap, it has four wires coming off the secondary: 280-0V@70mA AND 6.3-0V@2A. There is a pilot lamp and it is run off the heater (6.3V) voltage and it lights up fine when I have the amp disconnected from the power transformer, lights up dimly when amp is connected and run through current limiter.

[J M Fahey]

lights up fine when I have the amp disconnected from the power transformer, lights up dimly when amp is connected and run through current limiter.

What does "amp is connected" mean?
We want to know what happens when
a) transformer high voltage secondary is floating (both wires connected to nothing)
b) transformer high voltage secondary has one end grounded, the capacitor has the negative leg (or its can) grounded, the other transformer wire is connected to the anode of a 1n4007 and its cathode is connected to the capacitor positive leg ... and *nowhere else*.
Only these 2 options please.
In the second case, what voltage do you measure from ground to the capacitor positive leg?
And *your* drawing of

We need that schematic or this discussion is just some hot air.
We don't know how you connected your transformer, your diode, your capacitor.
Words are not precise enough, we need a drawing.
Please label all parts, as D1, C1, etc, plus showing its value.
Wire colors also.

would still be useful, thanks.

[Chuck H]

We need a "slap forehead in frustration" emoticon.

Please, with no reference to any previously posted diagrams, look at your actual test circuit and draw what you see. Include any grounds, diode and capacitor polarities please.

Other than that I would ask if there is any continuity between the HV and 6.3V secondaries with at least one of those two secondaries disconnected from anything? Disconnected from anything means both secondary leads floating in free air.