Re: Non-working Commodore PET 3016
 

Power on, black lead on known 0V, meter in voltage mode, what voltage do you see on pin 40 of the 6502?

Re: Non-working Commodore PET 3016
 

4.963v

Re: Non-working Commodore PET 3016
 

Another quick question - I do not have a chip in UD5 and the BoM gifs I have indicate there should be something in there.

What I do have is a spare 24 pin chip with no markings which was never in the PET while I have had it. Should there be anything in UD5?

Re: Non-working Commodore PET 3016
 

_Reset input state looks normal so it's odd you don't seem to have activity on the low address lines.

I'll have to wait until I get home before I can answer your question re: UD5 (technically at work just now). Anyone else?

Re: Non-working Commodore PET 3016
 

Hm. On the actual schematics (page 4), UD3, UD4 and UD5 are all marked as 6332 (SPARE), so I'm not sure there should be anything. Anyone's help appreciated.

Re: Non-working Commodore PET 3016
 

Might be worth checking the markings on the 6502 in case it has been swapped at some time in the past for a 65C02.

Check the voltage and if any frequency on 6502 pin2 RDY and pin 7 SYNC.

If no frequency measured on address lines pins 9, 10 and 11, what voltage is on those pins?

You could also check for frequency and voltage on any of the other address lines, pins 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25. Note if there is a frequency the voltage doesn’t really help, but if there is no frequency we might see what address the 6502 is stuck at.

Re: Non-working Commodore PET 3016
 

I'll check the voltages/frequencies as above - thanks Mark.

fyi, the scope I ordered two days ago from China has just been delivered....

Re: Non-working Commodore PET 3016
 

That's pretty good isn't it?

Can you link to a page showing the model you have (not on ebay if you can avoid it, but maybe you can find the same model on Amazon or elsewhere?). If we can see what you have it will help us to be more specific when asking you to make measurements.

If you are feeling lucky try using it to look at all the 6502 pins Mark suggested (as well as measuring for frequency and possibly voltage).

Re: Non-working Commodore PET 3016
 

Here it is. It's quicker than posting a letter to my Dad in Norwich....

https://www.amazon.co.uk/gp/product/...?ie=UTF8&psc=1

I need to install software on a PC and learn how to use it which I'm looking forward to so I'm doing the install right now and a bit of Youtubing to educate myself.

Re: Non-working Commodore PET 3016
 

Looks potentially very useful, especially with that logic analyser capability. I hope yours did come with probes. It looks like a possible clone of the 6022 Mark mentioned so maybe Mark already has a good idea of how to drive one of those?

Re: Non-working Commodore PET 3016
 

Lots and lots of probes

Re: Non-working Commodore PET 3016
 

In particular, I meant the 2 * scope probes as they might be expensive to buy separately if you didn't get them with the unit.

A good 'First look' would be that 1MHz signal we spent all that time looking for on UG5 pin 7. Now you'll finally be able to see what it looks like.

Re: Non-working Commodore PET 3016
 

No, I just picked that as a preference over the toy kit that colin originally considered. I had looked at the specs when I was looking for a scope last year, but went for siglent 200mhz dual channel instead.

Re: Non-working Commodore PET 3016
 

post #186

measured with my new meter (not the scope)

No frequency on any pins

Voltage on all pins (12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 24, 25) between 3.1-3.3

Colin.

Re: Non-working Commodore PET 3016
 

Did you check pin 2 and 7?

Re: Non-working Commodore PET 3016
 

Attached is a photo of the 6502.

Neither pins 2 nor 7 of the 6502 had frequencies

Pin 2 voltage 5.073V
Pin 7 voltage 0.134V

Re: Non-working Commodore PET 3016
 

No frequencies on pins 9, 10 or 11

Voltages:
Pin 9 - 3.56V
Pin 10 - 3.56V
Pin 11 - 3.57V

Re: Non-working Commodore PET 3016
 

Also still worth checking the markings on the 6502, just in case it has been swapped at some point.

If RDY is held low, that might explain why the address lines are held high with no activity.

As you have clock input and output on the 6502, but no address activity, if sync is also no activity and RDY is held high, then I would suspect a faulty 6502, but you should verify the previous measurements with the scope first.

I think the pet should be using one of the original nmos 6502, rather than the later 65c02, but that should be verified first by someone thats more familiar with pets.

Re: Non-working Commodore PET 3016
 

Mark, are you still having difficulty viewing the circuit daigrams online or was that just on one particular device? If you can't view them at all I can try grabbing them and emailing them to you.

This is where I wish my Sybex 'Programming the 6502' wasn't buried in the garage. It's probably been nibbled away to nothing by Silverfish by now.

I'll have a look to see where the input to RDY comes from on this system.

Re: Non-working Commodore PET 3016
 

The 6052 has

MOS
MPS6502
3979

markings on it.