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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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Thread Tools |
15th Apr 2021, 9:56 am | #41 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: Commodore PET working intermittently
John, a favour to ask - as you've probably seen there is another epic PET repair thread on the go - we are up to the point where you were a long time ago, needing to replace at least two of the IEEE 488 buffers.
I remember that the ones you bought were sold as MC3446 substitutes, but I can't remember what the devices were that you actually received and fitted. When you get a moment would you mind reading the part numbers off those? |
15th Apr 2021, 8:10 pm | #42 | |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
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15th Apr 2021, 8:36 pm | #43 |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
The actual numbers were 1820-1689 K8139
Hope that helps, J |
15th Apr 2021, 8:57 pm | #44 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: Commodore PET working intermittently
Do they look like this?
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16th Apr 2021, 3:42 am | #45 |
Octode
Join Date: May 2018
Location: Northampton, Northamptonshire, UK.
Posts: 1,440
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Re: Commodore PET working intermittently
I had tried looking again on https://dsmcz.com/prestashop/
that had been mentioned on the previous thread, I discovered via Googling MC3446 equivalent: https://www.vintage-radio.net/forum/...163589&page=13 However, it seems they no longer have any MC3446's (or the HP in-house part numbered 1820-1689 I've now tried). So the MC3446AP - £4+VAT at Cricklewood Electronics - now seem the cheapest / easiest for these (Unless there are now others with stocks of the 1820-1689 numbered one) |
16th Apr 2021, 8:55 am | #46 |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
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16th Apr 2021, 9:02 am | #47 | |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
Quote:
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16th Apr 2021, 9:02 am | #48 |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
My intermittent issue seems to be a problem with the reset line!
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16th Apr 2021, 9:04 am | #49 |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
There's this one for £14.39 https://www.littlediode.com/components/MC3446.html
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16th Apr 2021, 10:54 am | #50 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: Commodore PET working intermittently
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16th Apr 2021, 4:26 pm | #51 |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
It's the voltage levels I've been told. Someone is kindly looking at it for me - not sure it's coming out of full reset. The reset to the CPU is going low but not fully high. I think that could also be a bad connector issue too.
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16th Apr 2021, 4:39 pm | #52 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: Commodore PET working intermittently
As it's already in hand and you don't have it at the moment anyway, we won't interfere with the process but we are always interested to know about causes and effects, so it would be interesting to know what your looker finds.
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16th Apr 2021, 6:57 pm | #53 |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
I will certainly update the thread when I know more. I also think one of the 3446s has gone bad. Luckily I had bought three way back when, only used 2 so had a spare!
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16th Apr 2021, 7:05 pm | #54 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: Commodore PET working intermittently
It it one of the recent replacements which you think has failed or is it the remaining, as yet unreplaced one? Interfaces like that are particularly prone to damage by connection / disconnection of an attached device while the power is on, so definitely don't get into the habit of doing that.
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16th Apr 2021, 8:05 pm | #55 | |
Hexode
Join Date: May 2013
Location: Middlesbrough, North Yorkshire, UK.
Posts: 442
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Re: Commodore PET working intermittently
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I will definately not do the connection/disconnection whilst power is on again! |
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