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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 26th Apr 2021, 7:42 pm   #1781
ScottishColin
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Default Re: Non-working Commodore PET 3016

Ah - it's here then?

All I need to do now is work out how to secure the end of the wire...

Colin.
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Old 26th Apr 2021, 7:49 pm   #1782
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Default Re: Non-working Commodore PET 3016

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Originally Posted by PJL View Post
An epic repair with 1770 posts. Having watched this thread from near the start and having been in electronic design and programming using early 8 bit CPU's back in the 80's, you almost had me longing for a pet...but the number of faults has thankfully cured me of that.

I don't think all PET's will have suffered so many different IC failures (I seem to recall it may have got upto 20 on Colin's list!)
- and not quite sure what happened to this one (If all the RAM IC's had failed, some Commodore-specific ROM's then that may have been less surprising, as these don't always have to great a reliability compared to most simple TTL IC's)
However, original PET's are currently rather collectable & fetching rather-high prices, so they are now still well worth repairing .

But you could always build a modern clone (still using the same original main IC's types, but using modern CMOS versions that are still being sold in DIL and a lot simpler RAM without lots of obsolete IC's), for not too much.
And probably managing to eliminate quite a few of the original buffer IC's that had been responsible for many of the problems on this one.
- Like the one I recently saw in this article that featured new clone design, smaller PCB: https://www.eevblog.com/forum/projec...programmer/75/

It's a lot closer hardware-wise to an original, so should allow you to use all the addons, compared to just using an FPGA dev board / RPi or a PC to emulate one at software-level.

Last edited by ortek_service; 26th Apr 2021 at 8:01 pm.
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Old 26th Apr 2021, 7:52 pm   #1783
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Default Re: Non-working Commodore PET 3016

The first 60 seconds of this video does a good job of showing how to do the discharge:-
https://www.youtube.com/watch?v=X0xn...JohnnyBareToes
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Old 26th Apr 2021, 7:53 pm   #1784
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Default Re: Non-working Commodore PET 3016

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Originally Posted by ScottishColin View Post
Ah - it's here then?

All I need to do now is work out how to secure the end of the wire...

Colin.
Yes - can see quite a film of dust / dirt over the top of the EHT-cap (and the monitor's PCB)

A croc-clip is quite useful (will need this for screwdriver end) - or slacken one of the screws and jam bare wire end under the large washer, before tightening.

The PET service manual may also give you instructions over where is the best place to discharge the CRT to.
It may also be a good idea to remove the PET mainboard first, as doen't want any ESD spikes zapping any IC's on that!

BTW There may also be an HT reservoir capacitor on the Monitor's PCB that gets charged to > 100V.
So may need to check that isn't still charged (measuring voltage on it with DMM etc.), before touching around there.
But if monitor runs OK, then that should normally discharge it quickly, after mains switch off.

Last edited by ortek_service; 26th Apr 2021 at 8:15 pm.
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Old 26th Apr 2021, 8:11 pm   #1785
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Default Re: Non-working Commodore PET 3016

See attached.

I can't stress enough, the other end of the wire must be securely connected to the tube frame before you try to discharge the tube. Keep the wire itself well away from everything else in the monitor and don't forget to disconnect the monitor from the PET mainboard.

When you are sure you are properly set up, slip the tip of the screwdriver in underneath the edge of the cap, aiming for the centre of the rubber cap, and keep going until you hear a click / zap, and then keep going a little further until you hit something solid. At no point will you need to apply any force.
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Old 26th Apr 2021, 9:43 pm   #1786
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Default Re: Non-working Commodore PET 3016

OK - all safely out. Before photo and after cleaning with cotton buds/IPA attached. I'll leave it now and give it one more go in the morning.

Thanks all for your help.

Colin.
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Old 27th Apr 2021, 7:02 am   #1787
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Default Re: Non-working Commodore PET 3016

Looks better already. The monitor thankfully does not seem to have suffered from the damp as much as the main board did.

While it's spread out like that take lots of well-lit photos, especially of cables / connections, in case any of the wires fall off while you are handling the various parts.
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Old 27th Apr 2021, 9:01 am   #1788
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Default Re: Non-working Commodore PET 3016

For the record, here's a couple of videos I found useful regarding CRT discharging:

https://www.youtube.com/watch?v=x1DeMOl_nK4

https://www.youtube.com/watch?v=mParOYnZ3Fw

And one regarding a PET chassis clean-up/motherboard replacement.

https://www.youtube.com/watch?v=c3ib_rGNUKA

Colin.
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Old 27th Apr 2021, 2:34 pm   #1789
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Default Re: Non-working Commodore PET 3016

Yes, I recall seeing that PET 'restoration' video before
- Where they ended-up with a bit of a modern Hybrid-PET, having to put a new 'clone' Mini PET motherboard from Tynemouth Software in it as original was missing. So rather less original!
Although it's fortunate that this Mini PET board was designed to have the connectors in the same positions, to match cut-outs in the case.

However, it cost them rather a lot to do this, as the Mini PET is quite expensive (200 as a kit or 300 assembled! although it seems you do also get a Keyboard PCB with it) for what's on it, from looking at this Youtube video on assembling one: https://www.youtube.com/watch?v=zHAIuE5BQWk

But it could be you're paying a bit for their work in redesigning the video circuitry, to have firmware in an Atmel ATMEGA164P20 uC implementing a CRTC IC etc. (I presume they've used the Kernal from the later 8032 etc PET's that had a CRTC IC and allowed 80 column etc.)

I'll have to see how much the IC's they've used on the Mini PET - particularly the large DIL package IDT 1K Dual-port video RAM, compare in price to the ones they used here: https://www.eevblog.com/forum/projec...programmer/75/
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Old 27th Apr 2021, 4:31 pm   #1790
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Default Re: Non-working Commodore PET 3016

It's a shame Colin didn't keep a 'video diary' of his exploits here from the beginning but the end result would probably have been too long to fit on Youtube.

I haven't (yet) watched the third item in Colin's post #1788 but the original mainboard would have to have been sawn in half before I would give up on it - and maybe not even then - so it's hard for me to imagine a scenario where someone would actually remove the original main board and replace it with a functional modern replica.
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Old 27th Apr 2021, 5:36 pm   #1791
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Default Re: Non-working Commodore PET 3016

I did think of it but too late....there's plenty of photos along the way though. And I think this whole thread tells a story too.

I did think about a Mini PET motherboard before all I typed in my first post, but I wanted to try with this one - I'm glad we all stuck with it.

I've been taking all the electronics out of the case (incl. the CRT) today and have started rubbing things down with wire wool and a dremel. I've done the monitor case and the inside of the black base. I'll do some more tomorrow then choose a colour I like to start the respray.

I think I'll mask the labels as they look really difficult to get off in one piece.

Colin.



Quote:
Originally Posted by SiriusHardware View Post
It's a shame Colin didn't keep a 'video diary' of his exploits here from the beginning but the end result would probably have been too long to fit on Youtube.

I haven't (yet) watched the third item in Colin's post #1788 but the original mainboard would have to have been sawn in half before I would give up on it - and maybe not even then - so it's hard for me to imagine a scenario where someone would actually remove the original main board and replace it with a functional modern replica.
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Old 27th Apr 2021, 5:42 pm   #1792
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Default Re: Non-working Commodore PET 3016

Quote:
Originally Posted by SiriusHardware View Post
It's a shame Colin didn't keep a 'video diary' of his exploits here from the beginning but the end result would probably have been too long to fit on Youtube.

I haven't (yet) watched the third item in Colin's post #1788 but the original mainboard would have to have been sawn in half before I would give up on it - and maybe not even then - so it's hard for me to imagine a scenario where someone would actually remove the original main board and replace it with a functional modern replica.

It would have to be a time-lapse building-work style one.

In that Trash to Treasure. PET 2001-32N restoration video, he did actually fix the board that was in it when he first got it.
But he said it was actually an incorrect one - from an 8032 model. And he said he sold that board (presumably for someone to fix an 8032 etc), as he wanted something closer to the original 2001 spec.

So I guess you can configure the Mini PET to what model PET it appears to be.
- But could probably do something similar with the 8032 board, possibly using the older Kernal ROM (if they did support the CRTC).

And I had read that Commodore had originally used upto 4 different boards in some of the PET's/ CBM's. So the model number on the front wasn't a great guide to the board, and needed to lift the lid / 'bonnet' to take a look.
Although the PET 2001 was the original model, and later replaced by the 3000 etc. series, but the 2001-32N was probably a later 'N' version of the 2001 so that may have been made concurrently with some other models.
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Old 27th Apr 2021, 7:52 pm   #1793
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Have you looked around to see if anyone is selling reproduction / replacement labels? (I haven't but I have ordered replacement badges for my Atari STe in the past so I just wonder if someone has the PET covered as well).

I'm only thinking worst-case scenario - if you can preserve the original labels intact then obviously you should, but it would be useful to know whether you have a failsafe to rely on.

It might be an idea to scan or photograph the original label square-on so that if the worst happens you have a good record of what the original looks like, you might then be able to print a realistic looking replica yourself. Same goes for any other original labels and markings, if you have good hi-res photos you have a reasonable chance of producing a close replica should anything untoward happen to the originals. I know your CAD skills must be well above average given the quality and variety of the items you produce with your 3D printer.
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Old 27th Apr 2021, 8:21 pm   #1794
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Default Re: Non-working Commodore PET 3016

There is a guy on eBay selling 2001 style PET labels so possibly someone is making them for the 3000 series. He might be able to get one for you?
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Old 27th Apr 2021, 9:08 pm   #1795
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Default Re: Non-working Commodore PET 3016

Yes - I've seen them. I guess I'm still trying to keep as much as I can of the old if possible, even to the extent that the vinyl large label has some rust marks down it, but I think I'm not going to to be too worried if that doesnt clean that off. - I'd rather keep the original label on the case.

There's also a silver label on the monitor at the back as well as three on the back of the black base. Also there's some QC stamps on the inside that I'd like to retain if possible.

It's interesting to see the painting on the inside - you can see where they left the prop when they sprayed as there's no paint on the chassis behind it. It clearly didn't get many coats on the inside.

Colin.


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There is a guy on eBay selling 2001 style PET labels so possibly someone is making them for the 3000 series. He might be able to get one for you?
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Old 27th Apr 2021, 9:12 pm   #1796
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Default Re: Non-working Commodore PET 3016

I was wrong - there's only two labels on the back. Photos attached.

Colin.
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Old 28th Apr 2021, 9:03 pm   #1797
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Default Re: Non-working Commodore PET 3016

Difficult labels off with the careful use of a laminated pouch and a hairdryer.

Colin.
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Old 28th Apr 2021, 10:44 pm   #1798
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Default Re: Non-working Commodore PET 3016

An idea - while they are off, make high quality scans of them.
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Old 28th Apr 2021, 10:46 pm   #1799
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That's a really good idea. Ta.

Colin.

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An idea - while they are off, make high quality scans of them.
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Old 29th Apr 2021, 9:18 am   #1800
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Default Re: Non-working Commodore PET 3016

I appreciate the care you are taking to preserve the history of this machine by retaining as many of its original features. Too many retro restorations I have seen erase the marks of use over the years and return something that looks brand new but is not quite "right". It's a difficult balance, how much do you repair and how much do you leave? But I think that repainting the case in this machine is a good move given that the rust is so severe. If the existing front label can be preserved then that will be good too, as I imagine getting an authentic replacement that doesn't look odd will be hard, and presuming it is still OK then any minor scuffs are just "patina"
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