Plate voltage problem (solved)

[mr_hankey]

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[Structo]

Make sure you have the correct cathode resistors connected to the proper triode.

In other words, check to see if the first triode which has the 220K plate resistor correlates with the 3.3K cathode resistor on the first triode.

Easy mistake to make on these amps.

[hans-jörg]

Hi,

the 133V and 3V at OD1 are suspect. Check solder joints at anode wire until cathode.

Best
Hans-Jörg

Edit: i read now you checked there. Nevertheless its somewhere there.

[mr_hankey]

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[mr_hankey]

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[JazzGuitarGimp]

Have you tried wiggling the tube in the socket while you have signal passing through it?

[mr_hankey]

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[mr_hankey]

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[Structo]

Good job finding the problem.

Rock on!

[rogb]

SOLVED!

I noticed that the very act of measuring the voltage on OD1's grid made the problem a lot less severe. It still sounded bad, but the gating effect stopped. Chopsticking the gird resistors and leads did nothing. Eventually I realized that the multimeter must be providing a ground reference, and lo and behold, the 'ground leg' of the OD trimmer was not connected to ground. Its ground wire must have come off when I changed the cathode resistors, because it was connected in the same eyelet. That wire is neatly hidden (and unreachable) underneath the board, so I couldn't see it.

Now that I've added a new ground wire to the trimmer, the OD channel works! This may have taught me a thing or two about using hidden wires.

Well done, my last 2 builds all buss wires have been on top of the boards, it ain't pretty but it works!

[CHIP]

I don't know if you used a backup board on your preamp board or not, but I've learned that if using eyelets and running wires under the pre board, a backup board adds a little more security in that if that wire comes loose during switching components and resoldering it still is partually held in position. Of course the underneath wire should be "hooked" over top of the eyelet. I think HAD actually used the backing board to slightly squeeze all those wires into a permanent position. Just an opinion.
One reason why I like turrets is that I can drill a small hole next to the turret, bring the wire up through the hole and wrap it around the turret. Then I can see that a wire from under the board is securely attached.
Just my way of doing things.

[mr_hankey]

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