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Old 8th Mar 2021, 9:19 pm   #833
ScottishColin
Octode
 
Join Date: May 2012
Location: Perth, Scotland
Posts: 1,762
Default Re: Non-working Commodore PET 3016

Couple of notes:

UI11 2 and 3 measure 0.61 (with the meter set to 2k) and the rest of the pins on UI11 0.71 to +5v. Is that significant? There's a similar drop when I measure to 0V.

All RAM chips pin 16 give me (c.) 0.25V

Apart from that seems OK. Some pins need a bit of scaping to give me a reading; I'll get them cleaned up.

Colin.




Quote:
Originally Posted by SiriusHardware View Post
You can try (with power off) making resistance measurements from the following points to 0V and to +5V

UJ2 pins 5,7,6,12,11,10,13 (Lines FA0 to FA6).

Also from the following points to 0V and +5V,

UI10 pins 8/9, UI10 pins 6/7, UI10 pins 4/5, UI10 pins 2/3
UI11 pins 8/9, UI11 pins 6/7, UI11 pins 4/5, UI11 pins 2/3

As usual for this sort of measurement,
The measurements from the UJ2 pins to 0V should all be about the same,
The measurement from the UJ2 pins to +5V should all be about the same,
The measurement from the UI10 / UI11 pins to 0V should all be about the same
The measurement from the UI10/UI11 pins to +5V should all be about the same.

No need to report them all individually but if you see something which looks like an odd man out, let us know.

And with power on, check voltage on each of UJ2-UJ9 and UI2 to UI9,
Pin 8 = +12V
Pin 9 = +5V
Pin 1= -5V
Pin 16=0V.

When doing these voltage checks be exceptionally careful not to slip and short pin 8 (+12V) to nearby pin 7 on any of the ICs.
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