Help with Troubleshooting Volume Control (Aiwa Mega-CD)

This is the volume control board (board 02) from one of the Aiwa Mega-CD units I have.
Left channel audio is present even when the volume is turned right down but does not turn up at all either.
The right hand channel appears to be working well, turning it up increases volume, turning it down results in no sound.
If I had to guess I'd say that the volume control variable resistor / potentiometer (VR802) is busted.

If anyone else has any ideas or could confirm this is the most likely fault, that would be most helpful.
Especially since I have no experience in troubleshooting resistance based components.
I've stuck some measurements down the bottom. The 01-02 board is known working so is a good comparison board.

And if it is the VR802 that is broken, any ideas on where I'd source a replacement?
From what I can tell there's a lot of three pin and six pin ones. B50K right?

Thanks in advance to anyone who can help! :loyal:








=============================================
01-02 Volume at Min (Measurements at 20K Setting)
TL 9.60
GND 0
TR 9.04
Ro 0 (2.5 on 200 setting)
RI 3.58
RI 3.57
Lo 0
=============================================
02-02 Volume at Min (Measurements at 20K Setting)
TL 9.73
GND 0
TR 9.72
Ro 0.05 - 0.20 (30 - 90 on 200 Setting)
RI 3.57
RI 3.71
Lo 0
=============================================
01-02 Volume at Max (Measurements at 20K Setting)
TL 9.59
GND 0
TR 9.03
Ro 3.58
RI 3.58
RI 3.57
Lo 3.58
=============================================
02-02 Volume at Max (Measurements at 20K Setting)
TL 9.73
GND 0
TR 9.72
Ro 3.8 - 7.0 (Jumping Around)
RI 3.57
RI 3.71
Lo 0
=============================================

 

Yep, there's still definitely trouble with that potentiometer alright!
Anyone know what these markings mean?



Here's a snap of the actual potentiometer. Markings on the side are
Panasonic 50KΩB 402M MAL A
Does anyone have any ideas on what a suitable replacement would be?



I started looking for some sort of schematic for the mainboard in the hopes of working out what should go where.
I figured that surely Aiwa would have based the CSD-GM1 off something they already had to save on costs.
And look what I found - Aiwa CSD-EX03, released only in Japan as well from what I can tell.



Same layout, missing the Mic Amp board from the back left, everything else seems to be in place.
Which reminds me, I don't actually have a photo of either of my Aiwas in one piece!



And then I found the Aiwa CSD-EX80... Date stamps of 96, CSD-GM1 was 94.

 

I have one of the top ones. Definitely not Japanese only. Actually, I think it may have been thrown out.

 

Ah don't say that! A piece of history died that day!
I had no idea Aiwa got eaten up by Sony and then disappeared off the face of the earth.
Poor Aiwa! :sorrow:

 

If it was chucked, I don't think I even had a say in that one. Like our television that was in the family (working) since 1972.

To be honest, I wasn't that bothered - it was a nice unit but I didn't even know it was faulty. Probably the CD drive. If it had been the Mega CD, then I'd have hidden it, of course!

 

:encouragement: That's the spirit!
Well the Aiwa CSD-EX80 has hit the shores of Australia.
At the very least I'll be pinching the volume knobs and 7-pin potentiometer for the CSD-GM1s.
And I might be able to get some decent readouts on what the transformer is supposed to output to the mainboard.
Aaaaand here's hoping the internal design isn't overly different - I've still got a dead radio section in one of them too.

 

Well, great news! The CSD-EX80 has arrived and the volume potentiometer is a perfect match with 7-pins.
I also noted that they fixed the silkscreen on the labelling.
There are no longer 2 RIs, but an LI - Left input perhaps. It would make a lot more sense!

TL 9.73GND 0
TR 9.72
Ro 0.05 - 0.20 (30 - 90 on 200 Setting)
RI 3.57
RI 3.71
Lo 0

Either way, glad to have this part of the saga sorted! :encouragement: