PET-style keyboard reassembly

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FriedOrange79
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PET-style keyboard reassembly

Post by FriedOrange79 »

Hi all,

Some time ago I bought an early VIC with the PET-style keyboard, but when it arrived the keyboard's PCB had suffered a rather catastrophic fracture:

Image

When I finally got around to fixing it recently, I glued the board together with epoxy resin and scraped off the green solder mask in a few spots so I could bridge across the breakage with solder where possible (at the far left and right edges, where there were no multi-layer sections). Mostly, however, I had to attach wires between the random small holes all over the board and the bit that broke off.

That worked well and I was able to mostly reassemble the repaired keyboard, apart from the F7/F8 key. It is different from all the others and seems to fit onto the black stems backwards compared to them. Does anyone know the details of this key? Is it supposed to match up with a unique part (like one of the white plungers, which only seem to fit in one way) that I inadvertently used elsewhere? This reassembly has come over a year since I dismantled it so I've long forgotten how it came apart!

Unrelated anecdote: another one of my VICs has that dreadful mushy keyboard which uses little silicone domes instead of coil springs; one of the black conductive spots was ruined from a previous owner's botched repair (which I can't fix since half of the broken stem is still superglued into the key...). Anyway, while I've read about repairing these contacts at great expense with some kind of conductive paint, I just stuck on a small scrap of aluminium foil with a glue stick and it's worked fine for over three years now.
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MCes
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Re: PET-style keyboard reassembly

Post by MCes »

For your PET-style keyboard consider the possibility of replacing the entire PCB.
You can get a PCB from an old (yellowed) standard keyboard.....
I think that it can work!
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." (Albert Einstein)
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FriedOrange79
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Re: PET-style keyboard reassembly

Post by FriedOrange79 »

MCes wrote:For your PET-style keyboard consider the possibility of replacing the entire PCB.
That's not the issue - I successfully got the PCB working again.
tl;dr: the problem is that I can't reattach the F7/F8 key because it doesn't fit on properly. I probably used the matching parts elsewhere by mistake but I wanted to ask in case someone actually knows how this keyboard fits together.
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eslapion
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Re: PET-style keyboard reassembly

Post by eslapion »

MCes wrote:For your PET-style keyboard consider the possibility of replacing the entire PCB.
You can get a PCB from an old (yellowed) standard keyboard.....
I think that it can work!
You think it can work because you didn't notice every single keypad contact is hard gold plated. Don't even think of using HASL or tin in there; carbon buildup will render the keyboard unusable in the blink of an eye.

ENIG will do you no good either - it's too thin. Making a PCB replacement with the correct hard gold plating for a single PCB would cost a fortune.
FriedOrange79 wrote:That's not the issue - I successfully got the PCB working again.
tl;dr: the problem is that I can't reattach the F7/F8 key because it doesn't fit on properly. I probably used the matching parts elsewhere by mistake but I wanted to ask in case someone actually knows how this keyboard fits together.
I suppose I have to take photos of my VIC-20 with PET style keyboard's underside for another thread. Might as well take more photos of the function keys at the same time.

I should be able to do it today or during the week-end.
Be normal.
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FriedOrange79
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Re: PET-style keyboard reassembly

Post by FriedOrange79 »

Thanks, eslapion. That should be a great help!
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MCes
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Re: PET-style keyboard reassembly

Post by MCes »

FriedOrange79, Pics can help in understanding your problem and the relative solution....

I'm not proposing to re-make a new PCB for the keyboard,
but if it's necessary I was suggesting to get a working PCB froa another unused (or sacrificable) keyboard.
It can't be from a "normal" keyboard, but may be that the PCB of keyboard with "dome" pressing contacts could have the right contact points.
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." (Albert Einstein)
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eslapion
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Re: PET-style keyboard reassembly

Post by eslapion »

FriedOrange79 wrote:Thanks, eslapion. That should be a great help!
I can take the keyboard off the case for the photos but do you also need me to open up the keyboard itself?
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FriedOrange79
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Re: PET-style keyboard reassembly

Post by FriedOrange79 »

eslapion wrote:I can take the keyboard off the case for the photos but do you also need me to open up the keyboard itself?
If you could lift off the F7 key and the black stalk underneath and photograph that, so I can see how the white plunger is supposed to fit, that should help I think.

MCes, I'll post a couple of photos showing what I've done in a short while.
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FriedOrange79
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Re: PET-style keyboard reassembly

Post by FriedOrange79 »

The underside of the repaired PCB:
Image

The problem with the F7/F8 key:
Image

Note the bump on the left side of each white plunger and the corresponding slot in the black stalks. The stalk of the F7/F8 key fits on backwards compared to the other keys (which also messes up the angle of the key), and the white plungers only fit in one way around. I did notice that the plunger for the spacebar fits in either way round - I'm not sure if that's relevant to my problem or not (I simply fitted it facing the same way as all the others).

I didn't have any black electrical tape, as you can see. Once it's all put together you can't see the blue tape anyway so it doesn't matter, as long as it keeps dust from entering.
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MCes
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Re: PET-style keyboard reassembly

Post by MCes »

Analyzing the last pic too I can see an insert-key on black piston and in the gray socket, but for F7 the insert-key is reversed, so it will be necessary rotate of 180° the gray socket or to extract the black piston from the cap-key, rotate it of 180° and refit it inside the cap
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FriedOrange79
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Re: PET-style keyboard reassembly

Post by FriedOrange79 »

Thanks for your patient suggestions MCes, but unfortunately I can't do either of those things. I can't rotate those parts by 180 degrees because they only fit one way round.
I'm going to partially dismantle the keyboard again today, to see if there was anything I missed.
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Re: PET-style keyboard reassembly

Post by eslapion »

As promised...
102_0798.JPG
102_0799.JPG
102_0800.JPG
102_0802.JPG
FriedOrange79 wrote:Note the bump on the left side of each white plunger and the corresponding slot in the black stalks. The stalk of the F7/F8 key fits on backwards compared to the other keys (which also messes up the angle of the key), and the white plungers only fit in one way around. I did notice that the plunger for the spacebar fits in either way round - I'm not sure if that's relevant to my problem or not (I simply fitted it facing the same way as all the others).

I didn't have any black electrical tape, as you can see. Once it's all put together you can't see the blue tape anyway so it doesn't matter, as long as it keeps dust from entering.
The slot in the black stalk is on the opposite side in my keyboard.

I'd say one of your plungers is misplaced.

Sidenote: The original black electrical tape has shrunk over the years leaving a trail of adhesive! :shock:
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FriedOrange79
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Re: PET-style keyboard reassembly

Post by FriedOrange79 »

Thanks again for that, now I know what to look for!
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Re: PET-style keyboard reassembly

Post by TheAnachronaut »

This late response might be of use to others. I encountered the same problem in a pet-style VIC keyboard. The answer is that Commodore simply used the same key stem for the F7 key, but they shaved off the little protrusion that makes it fit the correct way. One of the keyboard's key stems has been shaved, it's just been lost since it can fit on any other key, normally. If you install the F7 key first, you can simply go through the whole set to find the shaved key, or you can install it last and shave another stem to suit the F7 key (what I did).
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