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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 16th May 2012, 9:31 pm   #1
ScottishColin
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Default Dead Commodore Pet

A bit of background; I first got a Commodore Pet when I was 15 in 1979 and it started me off on what I laughingly call my career. I spent many a long night typing in programs from magazines in the UK and working out what was wrong with them and learnt a great deal and learnt to be inquisitive too.

Therefore, I couldn't resist buying a non-working Pet locally (well, two and a half hours away) in Scotland for twenty five pounds. It has power - I can hear it. The monitor is getting power, I can see it glow orange at the back. All I need to do is get it booting.

So far nothing on the screen at all.

I'm starting from scratch. My electronics limits stretch to taking out chips and reseating them. I can solder. I have a multi-meter.

Can someone point me off in the right direction to start please? I know I'm being vague about symptoms, but that's because I don't really have any.

Thanks for any advice.

Colin.
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Old 17th May 2012, 1:14 pm   #2
mike_newcomb
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Default Re: Dead Commodore Pet

Hi Colin,

are you aware of:-

http://www.commodorepet.org/

Many experts there.

Regards - Mike
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Old 17th May 2012, 1:18 pm   #3
Freya
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Default Re: Dead Commodore Pet

If it was my BBC I would start check capacitors, it had several that needed changing to allow to boot.
The power rails should let you know what's missing, assuming it's not more in depth.
I too fiddled extensively with the BBC, never too much could be bolted onto it. Even now they seem to produce some clever drive or adaptor for them.


Good luck,

Steve
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Old 17th May 2012, 2:43 pm   #4
3nf
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Default Re: Dead Commodore Pet

Hi Colin
It's not easy if you don't have a 'scope.
If you let it warm up, and then switch the power off and on again quickly, do you get any random characters displayed on the screen? This will show if the processor is clearing the screen, or if the screen is not displaying anything.

Good luck,
Chris
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Old 17th May 2012, 7:13 pm   #5
ScottishColin
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Default Re: Dead Commodore Pet

Mike - thanks. Not found that one. Looks potentially useful.

Chris - nope. Nada. Nothing.

Steve - do you mean I should be able to see with the naked eye and capacitors that have gone?

Am I going to have to buy a scope and learn how to use one then? Happy to do so. Something new every day and all that.

But I'll be starting from scratch. I don't suppose there's is anyone from Scotland out there who I could appropriately reward for some help to fix this is there?

Thanks.

Colin.
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Old 19th May 2012, 9:00 am   #6
3nf
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Default Re: Dead Commodore Pet

Hi Colin,

So the screen is not displaying any characters. Next step, have you tried turning up the brightness control at the back of the monitor to see if there is a raster of some sort? If not, then it could be just a power supply problem. You say the CRT heater is glowing, that's a good clue. Next step is to identify the type of PET. In early ones, the monitors were powered from the main circuit board, but the 8032-SK model I have here is powered straight from the transformer as it has its own recifier and regulator. One common problem was burnt contacts on the connector between the transformer and the main circuit board.

I hope this helps.
Chris.
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Old 24th May 2012, 11:17 am   #7
Andy - G8MNM
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Default Re: Dead Commodore Pet

Colin,

I am 123 miles from you further north near Huntly, Aberdeenshire.
I am a computer tech and qualified electronics technician.
I have a workshop and scope and other test equipment etc.
If you wanted a scenic drive north you could bring it up to me sometime.
Let me know?
I recently passed on a couple of PETS for someone up this way.

Regards

Andy
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Old 24th May 2012, 8:25 pm   #8
ScottishColin
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Default Re: Dead Commodore Pet

Andy - thank you very much. I will let you know soonest. We are moving house so the pet has a slightly lower priority right now.

Appreciate the offer.

Colin.
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