Quick help measuring potentiometer frequencies

soop · 04/11/2018, 12:32 PM

can someone give me a quick heads up on how to measure the frequency of VR105 on a white CD unit?

Looking at this https://www.pcengine-fx.com/forums/index.php?topic=8926.msg396086#msg396086 guide, it says "Connect the counter lead (typically the red lead in a red/black pair) to Pin 1 of Connecter P6
Connect the ground lead (black) to Pin 5 of Connector P5"

But I can't see any markings for P6 or P5 on the board. Where am I supposed to connect the probes? I would have thought it was just on the pins of the potentiometer itself.

I also can't find many things with 5+ pins

NightWolve · 04/11/2018, 12:35 PM

I'd PM thesteve to get this noticed, I don't see him wander around as much as years past.

Psycho Punch · 04/11/2018, 12:42 PM

I'd help you but I think you mean the original CD unit, right? The Turbo Duo has the jumper connectors clearly labeled on the board's silk screen.

soop · 04/11/2018, 12:48 PM

Quote from: guest on 04/11/2018, 12:42 PMI'd help you but I think you mean the original CD unit, right? The Turbo Duo has the jumper connectors clearly labeled on the board's silk screen.

Yeah, the OG unit. It's all marked - like every single resistor - but the only Ps on here are two "test points" of 5 and 6 pins

soop · 04/11/2018, 12:55 PM

https://i.imgur.com/ojc1HaB.jpg

Here's the bottom of the unit. The potentiometers are at the bottom left, and the two test points are on the middle left and bottom right

NightWolve · 04/11/2018, 01:20 PM

Couldn't see your image at first, it gave an "imgur is over-capacity" error message. Interesting, but it worked on a refresh.

Psycho Punch · 04/11/2018, 01:40 PM

Soop, aren't the connectors on the other side of the board alongside the laser assembly? Doesn't make sense to place it underneath the board since you'll usually need a disc spinning to test the cd reader.

soop · 04/11/2018, 01:53 PM

Quote from: guest on 04/11/2018, 01:40 PMSoop, aren't the connectors on the other side of the board alongside the laser assembly? Doesn't make sense to place it underneath the board since you'll usually need a disc spinning to test the cd reader.

Ah, I'll check. I'd planned to temp solder some wire and clips to the pot and connect it to the multimeter that way.

Ok, I've just checked. The two test points, p103 and p104 are present on the other side, along with some connectors labeled p106 and 107 thaI can see, but no P5 or P6