Resistance issue [resolved]

[soundfel]

I finished my SEX 3.0 but had a dead right channel so decided to resolder everything on the A side and changed the pot to an Alps 100k. Now, every resistance on the B side is wrong, everything reads OL. I didn't touch anything on this side and the soldering seems OK. Any help is appreciated!

[Paul Birkeland]

B15 bolts to the chassis, is that 0 ohms?

For the rest of the terminals that should read 0 ohms on the b side, there's a buss of black wires that bounces between the terminal strips and terminates back at the high voltage power supply.  One of those wires has to be loose or missing for you to be betting OL on terminals that should otherwise be 0.

[soundfel]

Thanks for the reply! Ok, I rewired the pin a1/a12 cable and fixed a solder on 12L. I’m now getting 46k ohm at terminals 4 and 18 (should be 249k) but the rest are OK now. Any ideas?

[Paul Birkeland]

Why did you rewire the A1/A12 cable?  What did you replace it with? 

[soundfel]

I just thought it was in a bad shape after the first re-soldering and that maybe that was cause of the bad readings. I used the same kind of cable and the same connection (red A12 to B1, black A1 to B12 and drain to 15L).

[soundfel]

In case it helps, here's a picture of my build.

[bmkuter]

What's your pot wiring like?

[soundfel]

It is wired the same way as the stock pot was

[Thermioniclife]

Maybe its just the angle of the photo but I do not see anything connected to the wiper of the alps pot (pin 2)
This is what feeds the voltage amplifier grid of the 6fj7 pin 10 on that tube.

[Thermioniclife]

Without a grid load your going to have big problems. this load comes from the pot in this instance.

[soundfel]

Hello and thanks for your reply. I think it is the angle of the photo. Both wipers are connected to pin 8 on each side. Do you think I should go back to the stock pot?

[Thermioniclife]

I'm sure you can use the Alps pot but I feel that the circuit may be miss wired. please check that the wiper of the pot is soldered to pin 8
of the 6fj7 socket and the grid stop resistor. then make sure the grid stopper resistor is connected to pin 10 of that socket.
pin 8 is an unused pin for that tube that makes it a convenient mounting place to mount the grid stopper resistor. Having said that I still feel that perhaps your volume pot may be miss wired so perhaps a few more photos of the pot showing the connections to the pins could be useful.

[soundfel]

Thank for answering, here are some more photos

[Paul Birkeland]

Now that the resistances are OK, how are the voltages?

[soundfel]

Hello, Paul. Not looking good... I´m getting around 485v on terminals 2, 6, 7, 10, 13, 16, 20, 21, 24 and 27. The rest of the terminals on that section are 0v. On terminal 20 I get 20v, 487v on 33, 243v on 34 and 35 and 0v on 29, 31,32 and 36. It marks around 22v on H2, H3, H5 and H6, and 0v on the rest.