Resistance readings off [resolved]

[denti alligator]

Check the wiring on your balance pot.

It looks all good now. And anyway, I’m getting no L channel on the tape out that I wired, which bypasses balance and volume, doesn’t it? Seems to me like it has to be the selector switch, since the L channel is out on all inputs and outputs, no?

I tried reflowing all four center pins on it, but that hasn’t helped.

[Paul Birkeland]

It looks all good now.

Did you fix the error?  The error I see would short out the incoming signal of one channel.

Again, please don't use this preamp until the resistance checks are resolved.  It's actually possible to damage your source based on the error I'm seeing, though most have some built in protections for this kind of issue.

[denti alligator]

Yes, the error was fixed and the resistance reading is normal.

[Paul Birkeland]

Can you post some fresh photos of that part of the preamp?

[denti alligator]

Here you go. I tested resistance on the selector switch center pins and indeed there is a discrepancy between the red and white wired pins. So went ahead and retested all resistances and there’s a discrepancy between A5/A6 (measuring 5k) and B5/B6 (measuring 105k). These were both in range and only about 10k apart earlier today before I did the voltage check. Never mind: the balance pot was turned to one side. Once I balanced it, these figures became almost identical.

Thanks for your help!

[denti alligator]

Keep in mind that the L channel doesn't work even when the amp is not turned on! The tape out that I wired sends the R channel to my Crack, but not the L. All three inputs are the same.

[Paul Birkeland]

Can you post photos of the selector switch and tape RCA jack wiring?

[denti alligator]

Can you post photos of the selector switch and tape RCA jack wiring?

Bit of a mess, but here are some different angles.

[Paul Birkeland]

The black wires on the selector switch are grounds.  The white wire is L+, the red wire is R+.  You have a black and white wire connected on your selector switch, which isn't right, so you need to swap that pair at the tape output to correct for that.

[denti alligator]

The black wires on the selector switch are grounds.  The white wire is L+, the red wire is R+.  You have a black and white wire connected on your selector switch, which isn't right, so you need to swap that pair at the tape output to correct for that.

Ah, I see that. But will that also correct the other output?

[Paul Birkeland]

Ah, I see that. But will that also correct the other output?

What other output?  The one tape output channel that's wired correctly is working, the one that's wired backwards is shorting the output of the selector switch for that channel to ground.  When you correct that, you will make that channel work again.

[denti alligator]

OK. Great. I meant the output with green/blue wires. If this will fix that too, excellent. Thanks. I’ll report back.

[denti alligator]

It sings! Thanks. Sorry that adding this tape out introduced an extra troubleshooting step. I’m grateful for your help.

[denti alligator]

It really does sound wonderful. Bass seems to be more extended. The drive gives the music a nice kick.