UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Non-working Commodore PET 3016

ScottishColin · 11th Jan 2021, 5:11 pm

OK. I've gone through the whole thread to make sure I've missed nothing. Although I haven't made any advances, I have a couple of questions if that's OK.

Post 5 - I have not done this; we moved onto other things; is it worth me doing this?

Post 9 - all readings are consistent with the diagram

Post 18 - all readings are the same (within tolerance)

Post 38 - here's my questions. I'm confused.
I get readings on Pins 3 and 5 on J7 (c. 50Hz - varying) but only if I do not connect to earth. If I earth the meter, I get a zero reading. I cannot explain this - if anyone has any suggestions I'd be grateful.

The same is true using UH7 pin2 and UG10 pin 11 i.e. I get a reading when I connect the Red lead, but as soon as I ground the black lead, it goes to zero.

Post 43 - same readings

Post 46 - next question:
If I connect Black UG5 Pin8 to red UG5 pin 7, I get a zero reading
However, If I swap the leads (ie Red UG5 pin 8 to Black UG5 Pin 7), I get a reading of 1.298 M Ohms.
Does that make any sense?

Post 52
All readings for resistance from Black UG5 pin7 are between 0.001-0.003 Ohms

Apologies if this adds more confusion. I'm leaving desoldering UG5 Pin7 until last.....

Thanks

Colin.

11th Jan 2021, 5:11 pm	#83
ScottishColin Octode Join Date: May 2012 Location: Perth, Scotland Posts: 1,806	Re: Non-working Commodore PET 3016 OK. I've gone through the whole thread to make sure I've missed nothing. Although I haven't made any advances, I have a couple of questions if that's OK. Post 5 - I have not done this; we moved onto other things; is it worth me doing this? Post 9 - all readings are consistent with the diagram Post 18 - all readings are the same (within tolerance) Post 38 - here's my questions. I'm confused. I get readings on Pins 3 and 5 on J7 (c. 50Hz - varying) but only if I do not connect to earth. If I earth the meter, I get a zero reading. I cannot explain this - if anyone has any suggestions I'd be grateful. The same is true using UH7 pin2 and UG10 pin 11 i.e. I get a reading when I connect the Red lead, but as soon as I ground the black lead, it goes to zero. Post 43 - same readings Post 46 - next question: If I connect Black UG5 Pin8 to red UG5 pin 7, I get a zero reading However, If I swap the leads (ie Red UG5 pin 8 to Black UG5 Pin 7), I get a reading of 1.298 M Ohms. Does that make any sense? Post 52 All readings for resistance from Black UG5 pin7 are between 0.001-0.003 Ohms Apologies if this adds more confusion. I'm leaving desoldering UG5 Pin7 until last..... Thanks Colin.