• Please review our updated Terms and Rules here

Hello from a Reluctant PET Owner

ajgriff

Experienced Member
Joined
Nov 11, 2021
Messages
110
Location
Halifax, UK
Hello and thank you for having me. About thirty years ago I used to buy the occasional VIC 20, C64 or Spectrum from car boot sales when such things were unpopular and cheap. They were largely for the amusement of my children and although I'm a lifelong electronics hobbyist I never had to do much with the computers in terms of repairs. At the time I also acquired a non-working PET 2001-8 with calculator style keyboard which typically just displayed the frozen random character (garbage) screen at switch-on. Life was hectic back then so I'm afraid the PET lay untouched until earlier this year when I decided to see if it could be revived. The original intention was simply to get it working and then pass it on to someone with a greater interest in vintage computing. However during the restoration process I got hooked! So I'm here to learn more and hopefully pass on a few tips to anyone else faced with a non-working early PET. I should say that my knowledge of logic circuits and low level programming is still basic to say the least.

Alan
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,044
Location
UK - Worcester
Hello Alan and welcome to the forum - you have come to the right place for repairing a PET!

Yes, you can get hooked easily :)!

So, first things first, have you found the documentation treasure-trove over at http://www.zimmers.net/anonftp/pub/cbm/schematics/computers/pet/2001/index.html?

Second, what test equipment do you have? For example: a basic multimeter, a logic probe, and oscilloscope?

Do you have an EPROM programmer?

I wrote some test firmware for the PET a few years ago that you can program into an EPROM and pop in place of the EDIT ROM.

What devices on the main board are socketed?

You didn't actually say whether you got your PET working or not (now I re-read your post).

By the way, you will be moderated for the first 10 posts or so - so we will have to wait for the moderators to have a sensible conversation about repairs. Just post now and then and the overworked (and underpaid) moderators will eventually let you fly on your own.

You also ought to be aware that the private messaging system on the forum got 'screwed up' when we up (down) graded the board - so I would advise caution in using it. You generally get blank messages! As much use as a chocolate teapot in fact!

Dave
 

ajgriff

Experienced Member
Joined
Nov 11, 2021
Messages
110
Location
Halifax, UK
Thank you for the warm welcome Dave and for the advice about the forum.

I'm sorry I didn't make it clear that the PET is now fully functional. Luckily I didn't need much more than a DMM and an oscilloscope to track down a number faults. Fortunately the 6540 ROM chips weren't the cause of the problems so an EPROM programmer wasn't required.

I've been a member of the UKVRR&R forum for many years and, as you may know, there are a small group of contributors there who are interested in vintage computing. Their guidance and encouragement was invaluabe. However now I've become more interested in the PET and how it works I thought it would be logical to join this forum as well.

Primarily for my own amusement, I've written up my experiences with the PET into the form of a booklet with photographs. It's all quite basic but I could post a Dropbox link to the file (it's quite large) if people think it would be of any interest to members here?

Alan
 

daver2

Veteran Member
Joined
Jun 19, 2012
Messages
8,044
Location
UK - Worcester
Congratulations on fixing your PET then! Another one saved from oblivion...

A DMM and an oscilloscope is pretty much the requisite test equipment. For the really stubborn PETs, a simple logic analyser makes things much easier - but those faults come along vary rarely.

The EPROM programmer would have been of use to burn my test firmware into an EPROM. My test firmware doesn't require working RAM to run the initial tests - and then starts to run an exhaustive test on the RAM itself. However, a couple of members have developed a 6502 adapter card and loaded my test firmware onto that (along with a load of other nice goodies)...

Yes, a few of the UKVRR&R members are on here as well...

Yes, always interested to read of other's stories and experiences.

If there are any specific questions you have about the PET and how it works, ask away :)!

Dave
 

ajgriff

Experienced Member
Joined
Nov 11, 2021
Messages
110
Location
Halifax, UK
Probably best if I create a new topic in the forum's Commodore section with a link to the restoration story PDF.

Alan
 

robert_sissco

Experienced Member
Joined
Oct 12, 2021
Messages
108
Location
Midwest U.S.A.
"PET owner" and "programming is still basic", I see what you did there.

Also hello and welcome to the club
 
Last edited:
Top