protek
"Takai desu ne." -"Jinsei da."
I've had this Vic-20 for some time now. It's otherwise working okayish but last time I used it I noticed that some of the keys require pretty determined key presses. I've been planning to do something about it a long time but until now I had not got around it.
I dug the Vic up and connected it to my TV. I went through all the keys that actually print something on the screen one by one, trying to apply the same kind of force on each press. To my surprise there where only couple of characters that didn't show: 'E' and 'M'. Both would show if I did a determined key press but "normal" typing didn't always show them.
So, off with the lid and disconnecting the wires from the motherboard. I then took the whole top section downstairs, where I have my soldering station. To get the membrane off the keyboard, you need to first unsolder two wires that are connected to the 'Shift lock' key. After that it's just unscrewing a gazillion tiny screws. You don't even need to separate the keyboard from the top section of the case.
I was surprised how good both the membrane contacts and the contact pads looked. This Vic hadn't seen much use in its heyday. The keyboard was also otherwise very neat and clean. There was no crud or dust, just an odd hair here and there.
Nevertheless, I dipped a swab into IPA and went through all the contacts on the membrane and all contact pads on the keys. The swab was only slightly yellow after going through the contact pads.
I then put everything back together, re-soldered the 'Shift lock' leads and went back upstairs to reassemble the Vic. I then connected the leads and turned power on and again typed in all the keys. This time everything showed on the first time. Funny how everything looked OK to the plain eye but the swabbing still made a difference.
I also noticed a bit of a glitch on the Vic when powering it up from cold. The display was kind of a negative, when first powered up and only after a few minutes of use the correct colors came up, first flashing and then permanently. Same repeated, when I tested it after the cleanup. I wonder whether it is caps or a bad solder joint in the video port?
I dug the Vic up and connected it to my TV. I went through all the keys that actually print something on the screen one by one, trying to apply the same kind of force on each press. To my surprise there where only couple of characters that didn't show: 'E' and 'M'. Both would show if I did a determined key press but "normal" typing didn't always show them.
So, off with the lid and disconnecting the wires from the motherboard. I then took the whole top section downstairs, where I have my soldering station. To get the membrane off the keyboard, you need to first unsolder two wires that are connected to the 'Shift lock' key. After that it's just unscrewing a gazillion tiny screws. You don't even need to separate the keyboard from the top section of the case.
I was surprised how good both the membrane contacts and the contact pads looked. This Vic hadn't seen much use in its heyday. The keyboard was also otherwise very neat and clean. There was no crud or dust, just an odd hair here and there.
Nevertheless, I dipped a swab into IPA and went through all the contacts on the membrane and all contact pads on the keys. The swab was only slightly yellow after going through the contact pads.
I then put everything back together, re-soldered the 'Shift lock' leads and went back upstairs to reassemble the Vic. I then connected the leads and turned power on and again typed in all the keys. This time everything showed on the first time. Funny how everything looked OK to the plain eye but the swabbing still made a difference.
I also noticed a bit of a glitch on the Vic when powering it up from cold. The display was kind of a negative, when first powered up and only after a few minutes of use the correct colors came up, first flashing and then permanently. Same repeated, when I tested it after the cleanup. I wonder whether it is caps or a bad solder joint in the video port?
