Recent content by Coder

They're all around great units. Very underrated in my opinion. You have built in ISA expansion, a great screen, powerful hardware for the time, and like you said, one of the best feeling keyboards to ever grace a computer, let alone on a portable one. I think the aesthetic is great, too. It...

Hi Dave. I meant to mention that I can set any of the available values and they are properly stored after power cycling, but the message remains. Also of note, on the first boot after replacing the CMOS battery, when I would expect the computer to be using it's default values for everything...

Hello everyone. I have a Sharp PC-7200 that when booting complains of "Invalid configuration information" and says to "Strike F1 to continue". When I got it, the original CMOS battery was dead, as you might expect. I've replaced it with the same voltage Ni-MH battery, and it now stores...

Looks like I may need to learn how to use that fancy oscilloscope I bought months ago. I should probably start by taking it out of the box... Yeah, these Sharps are definitely non-standard. Hopefully it's "standard enough" to glean some useful info from. I haven't been able to locate any of...

I'll have to post some pictures of mine once it's put back together. Mine is the dark gray variant. They're interesting systems. They even support a single full-length 8 or 16 bit ISA option card; a detail I'm surprised isn't discussed more when talking about these. That's a neat site. I...

Hello everyone. I recently acquired a Sharp PC-7200. I knew it wouldn't boot from the hard drive before purchasing. I thought it was going to be a PLUS+ HardCard like the PC-7100 and figured it just needed the rubber bumper replaced. Unfortunately, I found the 7200 is not a hard card, but...

I changed the capacitors out and that hasn't changed the behavior of the computer. The resistor now stays around 35C. I haven't checked the voltages yet, but kinda wonder if the PSU has been a red herring. When the computer is turned on, the keyboard lights flash like you'd expect. The power...

Yeah, that was in circuit. I've ordered the caps from mouser. They should be here tomorrow. I'll take the resistor out of circuit and see what it reads.

I've got another question for you. I recently got a thermal imaging camera attachment that plugs into my phone. When I turn on the supply, I see a SMD resister climbing to over 100°C. Am I correct that under normal operation, a resistor, especially one that small, shouldn't get nearly that...

I'm not sure I understand. When you say "the power rail it is fed from" are you talking about "VDD" (pin 1)? Because that is getting +5v. But the pin 7. labeled "C" on the datasheet diagram, is what's getting ~15v. I thought that pin 6 would be "inverse" of +15v, but I'll be honest, I don't...

I got this the other day and it won't turn on. I think it may be the caps on the DC/DC power board as I've read they are a common problem, as is usually the case in our hobby. I have replacements in my shopping cart on Mouser, but I wanted to verify the problem before ordering. I started poking...

If you can, upload the dump of the rom to archive.org so that others can use it to either repair their boards or maybe someday someone can reverse engineer a board. Thanks for sharing the pictures and information. It's invaluable!

One step forward, two steps back. I decided to look closer at the Dallas CMOS chip. I know that on some versions of the Dallas chips, they have a pin that holds the processor in reset if the battery has died. I'm not sure what the purpose of this was, but it means that if the internal battery...

Yep, the fuses are good. The second board never gets it's 24VDC input power from the first board, so they aren't really doing anything at this point anyway, but I did check them. I also tried applying 24VDC directly to the second board to see if that would get me anywhere, but it didn't help.

I guess I lied. The LED that indicates it's receiving power from the A/C adapter lights, but nothing else. I suspect there's a common flaw with these systems as I haven't seen any for sale that say they power on. Nor have I seen anyone with a photo or video of one booting. The only one of...