26th Sep 2022, 9:59 pm | #121 |
Octode
Join Date: May 2012
Location: Perth, Scotland
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Re: 1978 Commodore PET project
Is there any merit in me bending out UE7/3 here to have something to compare to? Mine has been replaced so is socketed so it'll be easy to do.
Colin. |
26th Sep 2022, 10:01 pm | #122 |
Nonode
Join Date: May 2004
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Re: 1978 Commodore PET project
The contact pads of the chiclet keyboard can be cleaned/restored without removing the keys as demonstrated in the video mentioned by Colin in post #66. I'd strongly advise against key removal.
Alan |
26th Sep 2022, 10:17 pm | #123 | |
Dekatron
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Location: Newcastle, Tyne and Wear, UK.
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Re: 1978 Commodore PET project
Quote:
We were just trying to think of how to replace the smallest possible number of devices necessary in BrackenFix's machine, but as he has already ordered replacements for all three I'm not sure if it wouldn't just be simpler to replace all three (one at a time, stopping at the point where the fault goes away) provided BF is completely happy that he can safely snip, remove and replace them. I agree that looking at the keyboard is good use of the intervening time, so maybe we can all stand down until BF lets us know when the replacement chips have arrived. |
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26th Sep 2022, 10:37 pm | #124 |
Tetrode
Join Date: Sep 2022
Location: Newton Abbot, Devon, UK.
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Re: 1978 Commodore PET project
I will keep you all up to date.
Luckily, I'm filming everything so you can see what I have done lol Will start on the keyboard in the next day or so |
27th Sep 2022, 11:05 am | #125 |
Nonode
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Re: 1978 Commodore PET project
The attached image shows my PET’s very grubby chiclet keys after cleaning in situ (ie, without removing the keypads). I used nothing more than a damp (not wet) cloth using warm water with a drop of washing up liquid added. It was a fiddly and time consuming task but there was no risk of breaking the plungers. The yellowing is the result of age and exposure to light. They could be whitened using the retr0bright process but this would again require keypad removal and I also don’t want to run the risk of lifting the print. With regard to de-soldering ICs, am I right in recalling that BrackenFix has bought a de-soldering station and some leaded solder? If so I’d suggest some soldering and de-soldering practice on a scrap PCB would be very worthwhile as mentioned earlier in the thread. Alan
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27th Sep 2022, 11:31 am | #126 |
Tetrode
Join Date: Sep 2022
Location: Newton Abbot, Devon, UK.
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Re: 1978 Commodore PET project
Hello
I am indeed getting a desoldering station and have got leaded solder and a practice board waiting I will definitely be careful with the keyboard and don't want to remove anything that isn't absolutely necessary |
27th Sep 2022, 5:59 pm | #127 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
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Re: 1978 Commodore PET project
Is there any way to verify the operation of the keyboard interface on the main board before starting any disassembly of the physical keyboard?
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27th Sep 2022, 6:06 pm | #128 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
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Re: 1978 Commodore PET project
The keyboard is just a matrix of switches, all the electronics is on the main PCB. Therefore briefly connecting a wire betweem a 'row' pin and a 'column' pin on the keyboard connector will simulate pressing a key. I am sure the electrical layout of the keys is in some available documentation.
However you do of course require a working main PCB for this to be useful. So that video fault needs fixing first. |
27th Sep 2022, 6:42 pm | #129 | |
Nonode
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Re: 1978 Commodore PET project
Quote:
Alan |
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27th Sep 2022, 6:58 pm | #130 |
Tetrode
Join Date: Sep 2022
Location: Newton Abbot, Devon, UK.
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Re: 1978 Commodore PET project
A few keys seem to work, especially if you press a bit harder than normal.
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27th Sep 2022, 7:05 pm | #131 |
Nonode
Join Date: May 2004
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Re: 1978 Commodore PET project
The last few minutes of the video posted by Colin show exactly what you need to do to get all the keys working. Here's the link again for ease of reference:
https://www.youtube.com/watch?v=WMKECAQjCH8 Alan |
27th Sep 2022, 7:11 pm | #132 |
Octode
Join Date: May 2012
Location: Perth, Scotland
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Re: 1978 Commodore PET project
Sandpaper is a bit interesting.
I used a sheet of plain A4 from my printer, folded it a few times and gently ran it over the plungers. It fixed most of the keys. For the few that didn't work, a slightly more vigorous going over with the paper fixed the problems. Colin. EDIT - I also cleaned the PCB with 99% IPA while I was there, but mine was nicely new (apart from a couple of broken traces) having been sealed up for 40+ years anyway. You might not need to do this if the cleaning plungers works. |
27th Sep 2022, 7:29 pm | #133 |
Nonode
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Re: 1978 Commodore PET project
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27th Sep 2022, 7:53 pm | #134 | |
Dekatron
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Re: 1978 Commodore PET project
Quote:
It makes more sense to do this when you can see what you are typing, so I would leave that stage until after the display section is working properly. |
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27th Sep 2022, 7:56 pm | #135 |
Heptode
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 663
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Re: 1978 Commodore PET project
Back in the mid 80's I was a CBM authorized svc tech. for a CBM ASC.
I quickly learned to use only machine pin sockets, as they were mechanically & electrically better than the cheaper ones. (I hated callbacks). If you really need a schematic, Howard W. Sams covered the 2 (USA) models of the CBM computers, and there is a slight possibility I may have OEM svc literature for the U.S. models still...maybe... That was 40+ years back. Mostly they wanted us a board changers. The highest failure item I ran across was the floppy drives failing. |
27th Sep 2022, 8:23 pm | #136 | |
Octode
Join Date: May 2012
Location: Perth, Scotland
Posts: 1,762
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Re: 1978 Commodore PET project
I have a dual disk drive 4040 that worked first time (well, after someone here helped me fix the power supply). I was somewhat surprised.
If you ever find those service manuals/literature, I'd love to see a copy (or even buy them off you if you're wanting to move them on). Colin. Quote:
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27th Sep 2022, 9:24 pm | #137 |
Tetrode
Join Date: Sep 2022
Location: Newton Abbot, Devon, UK.
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Re: 1978 Commodore PET project
Pretty.....
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27th Sep 2022, 9:42 pm | #138 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
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Re: 1978 Commodore PET project
I would have been glad if I'd looked as good as that when I was 40+ years old...
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27th Sep 2022, 10:04 pm | #139 |
Tetrode
Join Date: Sep 2022
Location: Newton Abbot, Devon, UK.
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Re: 1978 Commodore PET project
I actually said the same thing in my video
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27th Sep 2022, 10:16 pm | #140 |
Nonode
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Re: 1978 Commodore PET project
There’s one quick check that could be worth doing before getting to the de-soldering stage. Try running the machine with the socketed PIAs (UC6 and UC7) removed. Faulty PIAs are not uncommon and can cause display corruption. You don’t need to reconnect the keyboard to do this. An otherwise working PET will happily boot to BASIC without the PIAs although there won’t be a cursor and some of the interfaces won’t work. Alan
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