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ClockworkCoder

Keys c,v,n & m don't work when first pressed

by ClockworkCoder Sat Sep 15, 2018 11:13 pm

I currently have a strange issue with my keyboard. I'm not sure it's a recent issue - I've been starting to mod my A1200 (and just finished replacing the capacitors, which appears to have been successful), but hadn't previously thoroughly tested it - although 20 or so years ago, when I l had previously used it, it was working fine.

The symptoms are slightly odd, as the keys mentioned in the subject do work consistently, they just don't work when you first press them

* They work when you hold them down, and the auto-repeat for the key starts
* They work if you press one of them, then any other key (for example briefly holding "c" while pressing "n" (or any other key) prints "c" to the screen

This implies to me that it isn't a broken connection, but perhaps some interference(?) somewhere...

I've checked & cleaned the connector and ribbon cable, and they both look fine. I've also checked and cleaned again the entire board, and can't see anything obvious.

Does anyone here know what may be the cause? Is it likely to be the keyboard membrane? If so, is it fairly easy to do so to check / clean?

Many thanks, I really hope this is a (relatively) easy fix - especially as hopefully soon I'll be getting some replacement keycaps (black and white ones from a Kickstarter campaign)
User avatar
Dynamic_Computing

Re: Keys c,v,n & m don't work when first pressed

by Dynamic_Computing Sun Sep 16, 2018 8:03 am

A curious issue for sure! Does it happen before Workbench starts up? Do the two mouse button boot, and boot with no Startup-sequence, and see if the issue persists in the CLI. At least that way we can be 100% sure it is a hardware issue and not an odd software issue.
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ClockworkCoder

Re: Keys c,v,n & m don't work when first pressed

by ClockworkCoder Sun Sep 16, 2018 9:18 am

Hmm... thanks for the reply! I hadn't even considered that the problem could have been software, and it sounds worth a try.

Unfortunately in my impatience I opened the keyboard and checked the membrane, and there was a black mark on one of the traces which I've wiped off (I think it was just on the plastic surface), but everything else looked absolutely fine. So far so good, except that now I've tried it again, the characters "1", "Q", "A" and "Z" are now not working, which is almost certainly a problem with the membrane, as they all follow the same trace. I still can't see any visible issue in the traces though.

Also, to update, I found that someone was selling new keyboard membranes, which seem to have had good reviews, so I've ordered one of those - at least I'll have something else to compare against.

In the meantime, I'll try your advice and see if I can test the keyboard outside of Workbench.
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ClockworkCoder

Re: Keys c,v,n & m don't work when first pressed

by ClockworkCoder Sun Sep 16, 2018 9:42 am

Looking more closely at the end of the ribbon cable, there are tiny parts where it is transparent, so I suspect that it's been worn away. I may also try some conductive paint... although I don't think that's related to the original problem... which could be software.

This is a stupid question, but what's the easiest way to test if it's not Workbench? I'm only using a compact flash card with workbench, and a Gotek (now flashed with FlashFloppy's latest firmware)... is there a disk I could use to run some diagnostics / testing?

Thanks again
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Dynamic_Computing

Re: Keys c,v,n & m don't work when first pressed

by Dynamic_Computing Sun Sep 16, 2018 6:45 pm

Just hold down the two mouse buttons on bootup and you will go into the boot menu. There is an option to boot with no startup sequence and it will send you to a CLI (Command Prompt) - You can use most CLI commands from here. If by chance your keys work here (I don't think they will), you can type "run ed s:startup-sequence" and hit enter to open up the "ED" text editor. You can comment out lines that may be causing an issue by typing a ";" in front of them. Save the file by hitting "ESC" and typing "sa" and then hitting enter. Quit the Editor using "ESC" "q" and hitting enter.
The other thing to look at is user-startup in the same folder.
I am sure there is a diagnostic program on Aminet to test some hardware. You can create a bootable floppy and run that, too.
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ClockworkCoder

Re: Keys c,v,n & m don't work when first pressed

by ClockworkCoder Mon Sep 17, 2018 4:51 am

Thanks for that. I got to the boot menu, and needless to say, the keys didn't work from there.

I'll need to wait until either I can patch up the ribbon cable, or until the replacement membrane arrives before testing again. I'll also triple-check the connector... only other thing I can think of is if there's something else that might be shorting a connection there. I guess that could explain how those buttons could work at all... perhaps.
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Zippy Zapp
CA, USA

Re: Keys c,v,n & m don't work when first pressed

by Zippy Zapp Tue Sep 18, 2018 6:28 am

Do you have a multi-meter that you can check all the traces on the membrane for continuity? They are easy to follow from point to point and I would start at the traces that don't work and see if you can narrow down the break. Then you can use a circuit pen to fix the trace, possibly.

Sometimes the breaks are very hard to see.
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ClockworkCoder

Re: Keys c,v,n & m don't work when first pressed

by ClockworkCoder Thu Sep 20, 2018 8:37 am

Thanks @Zippy Zapp

Well, I started attempting to check the traces, but a combination of lack of time and concern that I might end up scraping too much off the contacts off led me to leave it for the time being.

However, yesterday I received the new keyboard membrane which works a treat... apart from...

It has the same issues with the c, v, n & m keys. Only this time, there was a slightly different issue. The left mouse was occasionally not working. More precisely, it wasn't working for selecting icons, although pressing on the left alt (to select the icon) a few times, it also worked.

Because both of these issues are sort of consistent, and at this point I don't really feel that it's software (otherwise it would be more consistent), I'm beginning to suspect that it's linked to the power supply.

So, I've now checked the pins with a multimeter, and they don't appear to be correct:

The top left pin (+12v) was fluctuating close to +1v
The middle pin (-12v) was fluctuating around -2.2v
The bottom-right pin (+5v) was pretty steady at 3.3v

I believe (please correct me if I'm wrong) that the 12v rails are for CD / floppy / HDD, and something related to audio, so I feel I'm lucky that the compact flash card requires very little draw from that.

I'm also thinking that because the 5v rail is lacking power, then that could explain the strange behaviour of the keyboard and mouse (mouse issue seems more inconsistent - it's a USB mouse plugged via an adapter).

Does this sound plausible?

Can anyone recommend a good power supply? Either something that's relatively simple to fit in to the original power supply case (not the wedge-shaped one), or a recommended pre-built alternative?
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intric8
Seattle, WA, USA

Re: Keys c,v,n & m don't work when first pressed

by intric8 Thu Sep 20, 2018 8:59 am

I can't help but wonder if your one or both of your CIA chips have gone bad. I'm no expert, but I believe they control inputs like mouse, keyboard, etc.

'Even' CIA functions: floppy control, serial control, some parallel port status
'Odd' CIA functions: parallel port, keyboard, some floppy support, joystick/mouse button number one.


As for power supplies for the A1200, I got one from Ray Carlsen and it is fantastic. He can literally build anything from scratch, 120/240 and even combo PSUs for multiple devices.
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ClockworkCoder

Re: Keys c,v,n & m don't work when first pressed

by ClockworkCoder Thu Sep 20, 2018 10:04 am

intric8 wrote:I can't help but wonder if your one or both of your CIA chips have gone bad. I'm no expert, but I believe they control inputs like mouse, keyboard, etc.

'Even' CIA functions: floppy control, serial control, some parallel port status
'Odd' CIA functions: parallel port, keyboard, some floppy support, joystick/mouse button number one.


As for power supplies for the A1200, I got one from Ray Carlsen and it is fantastic. He can literally build anything from scratch, 120/240 and even combo PSUs for multiple devices.


Wow, I hope it's not the chips - that sounds like it would be a real pain to fix :-/ Although I can't imagine what could have happened to make it go wrong, if they're the cause..?

Thanks for the recommendation. I may try to find something a little near to home first (UK), if I can, but I'll bear this guy in mind :)

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