Resistance readings off [resolved]

[denti alligator]

There are a few resistance readings that seem odd to me.

Terminal 9 reads 39.6k (terminal 19 reads 10k, as it should). I’ve reflowed this terminal with no difference.

A5 and A6 are about 24.93k, which I know is within range, but B5 and B6 read 105.2k

Also A3/A4 and B3/B4 had readings; they were not showing OL.

Note: I’ve reflowed all these and checked them carefully. Adjusting the balance pot appears to affect the numbers. Maybe that accounts for the discrepancy? (Vol and balance definitely change these numbers… Is that to be expected? Can I move on to the voltage check?)

 

[Paul Birkeland]

Terminal 9 reads 39.6k (terminal 19 reads 10k, as it should). I’ve reflowed this terminal with no difference.

Which terminal did you reflow? There are lots of terminals that need to be solid for the 10K resistance of the pot to be readable at that terminal.  I would bet you have a bad solder joint on one end of one of the black wires connecting to the level of the volume pot feeding that terminal.  It is really important to resolve this before powering up your Moreplay and trying to use it.

A5 and A6 are about 24.93k, which I know is within range, but B5 and B6 read 105.2k

This could well be the same problem as the issue at terminal 9.

Also A3/A4 and B3/B4 had readings; they were not showing OL.

What are the readings?

I would not power this one up, it's totally possible that you'd end up with excessive DC voltage on the center pin of the right RCA output jack, which is no bueno.

 

[denti alligator]

Thanks. I’ll go back to this tomorrow and report back. I reflowed 9 and whatever terminals were directly connected to it, maybe just the volume pot. What other terminals should I check to be sure?

These readings all fluctuated pretty signifanctly when I adjusted the volume and balance.

 

[Paul Birkeland]

You probably have a flaky ground connection.  These are the black wires.

 

[hmbscott]

I recommend you post a picture that shows the connections between the volume pot and the balance pot. There might be a misconnection in the ground wires, the black ones between the two pots. Or maybe in the twisted red/black wires at T2/A6, so a second shot of the A socket wiring would also help.

 

[denti alligator]

Ok, I reflowed T9, top and bottom front of vol pot, top and bottom front of balance, bottom rear of balance, and T2.

A3 1.2m and sinking
A4 1.1m and sinking
A5 21k
A6 20.8k

B3 1.07m and sinking
B4 1.02m and sinking
B5 59.8k
B6 59.6k

T9 79.2k

 

[Paul Birkeland]

You are definitely missing a wire in the region of the volume/balance pot.

 

[denti alligator]

Do my pictures help you see what’s missing? I can’t seem to see what’s wrong.

 

[Paul Birkeland]

Yes, you are missing a black wire in your volume pot/balance pot wiring.

 

[denti alligator]

Can you tell me where? I have two: one connecting top near tabs and one connecting bottom rear balance to bottom front vol. I must be overlooking another, because I don’t see one in the manual.

Never mind. I see it. I have the twisted pair on the bottom of the balance pot on the wrong lugs.

 

[denti alligator]

All well now, thanks for your help! Voltages were on. But the left channel is out. Troubleshooting now. Any tips?

 

[denti alligator]

This is just a signal path wiring issue. But it’s on all three inputs and both outputs. When I turn the Moreplay off it still only sends the R signal to my Stereomour.

 

[Paul Birkeland]

All well now, thanks for your help! Voltages were on. But the left channel is out. Troubleshooting now. Any tips?

While it looked like you were missing a wire between the volume and balance pots, what I actually see now is that the balance pot just isn't wired in correctly.

I still would not power up your amp until terminal 9 is reading the correct resistance.  Literally if you plug this Moreplay into a DC coupled solid state amp and turn it on, you may find a woofer cone departs your speaker cabinets and you have an expensive amp repair to pay for.

 

[denti alligator]

Resistance reading was normal after the rewire. Just trying to figure out the lack of L channel now.

 

[Paul Birkeland]

Check the wiring on your balance pot.

 

[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!