Markeno
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Posts posted by Markeno
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If it is 5 pin video, then it is the early model such as a 326298 board like my one C64. I expect the internal 5Volt 7805 regulator is overheating. They have a horribly inadequate heatsink. It will be made even worse if the 9V AC input is higher because that is what it works with. It is even possible the heatskink came off or came loose making poor contact with the 7805.
My 326298 had a very small heatskink riveted to the 7805, it was loose and not making good contact. It was also not enough of a heatsink for the task. I think some of those may even have been shown to have no heatsink. A modern replacement supply may very well have a higher 9V AC input to handle more current such as the 128, this is not a big deal on the later boards that have a much larger heatsink on the internal 7805. I have 2 new supplies, one with a bit higher AC so I keep that with my later board and the lower one with my 326298. I also put a larger heatsink on the 7805 in it.
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The 99/4a I got recently has a Mitsumi membrane type keyboard. The membranes fail, which mine is almost functional but not usable. So I got another 99/4a with the Hi-tek Stackpole keyboard. Like Ed said, today the primary source of a working keyboard is to find another 99 to get a working keyboard... I don't know what kind of keyboard the beige 99/4a I had decades ago was as it is long gone now.
I was looking at trying to repair or rebuild the Mitsumi. I was looking at the possibility to use microswitches like smd Alps ones above. I think that keyboard is a better option for such a conversion with the microswitches like that. It is built a fair bit like Commodore 64 Mitsumi keyboards with the plunger design. The keycaps are different, having a Plus shape to the contact, similar to Commodore 64 keycaps, but a different size. As long as the Hi-tek is working well I don't have to rebuild it though.
If you would be up to sending me the file, I could try printing the part on my printer. I doubt it is higher resolution. I had seen reference that people have done it, and that it does take a good bit of sanding etc to make them work.
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I will mention I found a post that the membrane picture was from. It indicated a possible fix that I don't believe was on the other referenced thread.
Still the 99 with the Stackpole keyboard came and the keyboard is in mostly good condition. All keys are working, although it is dirtier than I would like down inside, and difficult to clean properly. The contacts are all good, the key tops are all there and in good shape. Some of the stems are cracked of course, but at this point it is working well. Some corrosion though on the jumper leads, as well as a little on the pcb side. It wasn't kept in the best environment, attic or shed apparently uncovered/open box. It must have been quite dirty before the seller washed the keys, and most of the outer case.
Anyways, I will be looking into some way to revive the keyboard at some points. The other 99 although a bit rough looking internally due to the humidity and dirt it appeared to be working fine, so it will get a cleanup and I will look into if I can get that keyboard in a usable condition for it.
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Sorry to hear about the contact getting damaged. I hope you can sort it out somehow.
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I'd like to see how the 3d printing works out for you. I have the same keyboard, while it is all working, several of the stems there are cracked. It is apparently a common thing on them being thin like that.
They can be pulled out from the top with some pliers that have a bit of a grip on them. Anything smooth metal only will slip, but ones with the little ridges can be used to pull them. Still they are quite secure or at least the ones I tried. I don't know that I would try pulling them with the pcb removed. I figure they give that instruction, because it is expected to be a common failure, and not generally worthwhile to desolder the whole keyboard for one or two cracked stems. I debated that just to clean up mine due to some issues with it, but I don't have a desoldering gun type iron. The manual one I have works well for smaller tasks, I just wasn't up to using it for that many solder points. I had looked into them and seen a video that went over repairing Stackpole keyboards, which these are. There are two variations at least with the stems the one you have is the same as mine. I did pull one of the cracked ones out to inspect it, and see if it really did pull out and find what variation I had.
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There are options for the 80 column RGBI output, which is essentially CGA. I built one, but saw one that someone has been making recently. There were already some that were available. With options to go to RGB 15khz, then you can take that to VGA or HDMI. I don't know what 80 column software is out there to make it worthwhile though. Monochrome Composite is easy for 80 column though.
It is a better power supply. It sounds like bluejay's likely has a separation in the transformer. It is not a simple linear one like the C64 that cooks itself then the computer. Not that a linear supply is all bad, they are just old and not properly cooled.
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For more recent mostly original old gear that is mostly the Commodore stuff.
I have my two Commodore 64s. The first being a 250407 board, I then found a bargain on a 326298 that was in rough shape. A Commodore 128, I built a 80 Column adapter for use with it. Some 1541 drives, I built some Pi1541s for them, one with a Tapuino as well. For me much of what I like is fixing them up and getting them in good working condition again, or building things to go with them. Then getting some time to use them. There is also the TI99/4a that I got more recently, hoping to get back to having some fun with it.
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Being a kid in the 80s, I like the older stuff out there. We never had an Atari 2600 in the house, not until my Dad a light 6er at a yard sale in the late 90s. So I played on several of my cousin's a bit back in the day. I mostly remember playing at my on Aunt and Uncles when I went over there, I would get it out of the Attic and hook it up. Their boys didn't play with it anymore. We had a NES in the 80s at some point. I had and still have my original Gameboy, although the screen had been failing for years, that is sorted though now. I had saved up and got a Super Nintendo, and later a Sega Genesis Model 2 both left the house about 10 years ago and I wish they hadn't now. I had a Ti994/a beige model in the 90s before my parents purchased a 486DX2 66mhz in 94 I believe. Before that I had various of the Vtech simple basic computers which I loved playing with back in the day. I should still have two of the Vtechs, and need to find out where they are and what condition they are in. I guess I should findout and make sure they are ok and put them in a better place.
So I will post some of my more recent things I have been collecting. I had the Atari 2600 still with me, but I wasn't using it, and I figured my Dad might. I serviced it, the controllers and cartridge and switched it from RF to Composite Video and gave it back to him the other year.
So the only original system I have is my Gameboy DMG1. The screen was going, but I attempted a back light with the inverter. It looked so much better, but still was missing all the lines, even more actually. I replaced the LCD with one of the new ones. I am quite happy with it, although had my screen been repairable I would have been very happy with the backlight mod with the original screen. For me that was a very difficult mod, getting the backing off of the factory LCD was horrible with trying to not break the glass or cause damage to loose lines. In the end I lost more lines and it made it worse. The screen cover area was replaced with a Glass replacement that you can see broke, it was slightly to large and tight to fit properly. I have recently replaced the glass with a new one that I got fitted properly.
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I would think the easiest solution would be if someone were to make a new membrane. There are obviously people there that know how to reproduce good replacements for those kinds of keyboards. The process I believe ends up getting the mylar correct then they silk screen the traces on right? No modification, and in theory a reasonable cost. I did buy one of the new ones for a Z81 for my Timex Sinclair 1000. Although I haven't yet had to swap it out, the original is still working so far, although I haven't used it much.
It would be quite an involved process to get a full new keyboard designed and manufactured. I expect it would be out of the casual enthusiast interest due to cost though. Still for some who really are into them, I could see a wider interest due to their Alps or Stackpole etc keyboards being worn, or missing components etc.
Either of those options are well out of my area of expertise. I will probably try something with the Mitsumi one I have to get it into a usable condition, but I don't know what that may look like in the end.
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Well the market isn't big enough to get a commercial keyboard producer interested. I am just thinking it may be possible to retrofit the Mitsumi style keyboard with a board with tactile switches. The matrix as mentioned is nothing complex, it is about getting the switches in there, and the key stems being able to reliably press them. I don't know if those issues could be solved reasonably if at all.
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That adapter is a cool project. It is something to think about.
I just ordered a 99/4a for what I figured was near reasonable. It doesn't have a Mitsumi keyboard, and looks to be complete. I am still tempted to see if I can actually make a replacement board for the Mitsumi. I have enough other projects that I know are within my abilities though to keep me busy though.
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I am the most tempted by coming up with a replacement board, switching it over to some microswitches. It has been a month or more since I pulled the keyboard apart, I am not sure if it would be practical to attempt that.
The USB adapter there is to setup input to the TI from a modern usb keyboard then? Indicating even a wireless one. I would rather have a working keyboard on the computer if I can. I will keep an eye out for an Alps keyboard. It seems though they have what is called a "Stackpole" keyboard, I am seeing a number of 99/4as for sale with a missing key or so which are of that type. It doesn't sound like they are a great design either. I am not sure how I would reliablly be able to tell between it and the Alps model on an ebay listing. That is short of finding an Alps that is obviously broken, then I would need another for some switches for parts.. Seems like a bit of a mess.
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I should have noted that I have seen the Mylar fix post. I was not impressed with the likelihood of a fix, or at least a long term one. I haven't heard of any of the old vintage Mylar keyboards being properly repairable. I wanted to see if there was some reliable method found here. I'll likely attempt it at some point, but I am not expecting amazing long term results.
I am not yet happy enough with the 99/4a to invest another likely $75.00 to hope to get a good Alps keyboard, or least one that is repairable. I was very disappointed to find this unit had the Mitsumi. It is sad that it is so similar to the Commodore 64, except spring placement and being membrane. I would almost design a pcb replacement, except the stems don't have the conductive pads on the bottom, and the springs are setup differently and wouldn't work.
From what I read, I take it the multi keystrokes are likely "poor" condition contacts barely making contact, and sort of making it like it is bouncing? Being wired directly to the cpu inputs, it shouldn't be a circuity issue then?
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I was wondering if anyone knows of a way to repair the mylar type keyboards. The keys work, but many don't work well. Many take alot of pressure. But also many type multipule keys even with a very quick press. Is that that also the keyboard itself?
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Commodore 64 RF Video Issue Help
in Commodore 8-bit Computers
Posted
Standard 1.6Amp 250Volt Fuse. I think probably Fast Acting, not slow blow. I wasn't sure either what the 1 6/10 exactly was, I pulled up the power supply schematic and it lists a 1.6Amp Fuse.