UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

retromit · 14th Oct 2021, 9:27 pm

Quote:

Originally Posted by ScottishColin

As part of my fixing of my dilapidated PET linked to earlier, I had to buy a scope. I bought a generic 6022BL scope off Amazon and it did me fine. About £80-£90 right now. It needs a PC to plug into but I happened to have a spare laptop I could use. It works on Windows 10 and there's a Linux program/drivers for it too.

I learnt a lot about how to use them and still have it at the end of the process. There's plenty of people on here with far more knowledge than I that will have broader recommendations - just thought I'd mention what I used.

Colin.

Quote:

Originally Posted by retromit

Quote:

Originally Posted by SiriusHardware

I'm going to program up a 2716 with the 'Daver2' test code and send it off to Tim when it's ready so hopefully that will be available to use as and when we get to the point where we think the system can run some test code.

I may also do a second one with Slothie's code, the only reason that one is not an automatic choice is that I don't have a TMS2532 EPROM to program it into. It's just a lucky fluke that we can plug a 2716 into the UD8 position and it will work, whereas a 2716 plugged into the UD9 socket needs an adaptor to work. I might just 'adapt' a 2716 directly rather than place it in a socket adaptor.

With this one, I think we might have to start quite a long way back on the grid. The normal startup sequence is:
-Jump to boot code in UD9
-Shortly afterwards, jump to a subroutine in UD8.
-In the subroutine,
---Clear the screen RAM
---Initialise the large ICs
-Return from subroutine.

If the main system RAM is faulty then the machine will get stuck because it will fetch an invalid return address from the faulty RAM. But, it should still have managed to clear the screen by this point.

Unfortunately this machine isn't clearing the screen so right now, I'm not sure it will be able to execute test code either, unless we happen to have a dud original UD8 or UD9 PROM - it will still be worth trying one or other of the test EPROMs as a way of ruling out a faulty UD9 or UD8 respectively.

So now we come to the usual questions for retromit: What do you have in the way of test gear, in addition to the meter which you obviously do have..?

-Logic Probe?
-Frequency meter or Multimeter with a 'Frequency' range on it?
-Oscilloscope?
-Logic analyser or logic 'sniffer' with parallel inputs?

-Any other potentially useful test toys such as an Arduino Uno, Arduino Mega or Raspberry Pi?

Hi,

Many thanks once again for sorting the EPROM for me.

The multimeter I have is a bit basic. It has been planning to upgrade for a while now, so this could be an ideal time. Have you any suggestions on a good upgrade?

Unfortunately I don't have an oscilloscope or logic analyser (but, again, open to any suggesstions you may have). I do have a couple of Raspberry Pis, and also a 4116/4164 RAM tester (which is Arduino based) - which I was thinking of using to test the RAM chips from the PET (the 4116).

Tim.

Hi Colin,

Thanks for the recommendation - I'll certainly look into that.

Cheers,
Tim.