deramp5113's latest activity

You need to look at following signals during the 1st four cycles after RESET is released: 1) U24p1, U24p2 2) U22p3, U22p11 This will...

You‘ll also need to check U24 and U22 before passing off on item 4 Mike

The 909090 pattern means the CPU is running properly and has fetched a RST 7 instruction (0xFF) at some point. Upon fetching RST 7, the...

Great!

Remove the PCB from the key board frame and you can the “type” directly on the PCB pads wih your fingers and that typically works. Mike

Since it‘s the original CUTER ROM, then the mods to the PIO board must be to make it looks the same to the CPU as the keyboard port on...

To support the IMSAI PIO instead of the 3P+S board that CUTER expects for the keyboard, you may have a modified version of CUTER. If...

Ask over in the Heath SEBHC group, someone there can help. https://groups.google.com/g/sebhc

I have successfully created a Sol-20 Reproduction using Dave's great Sol-20 keyboard replacement. Might not have tackled this project if...

LOL, as usual, hindsight is 20/20 - so frustrating. We kept testing resistance +/-16v to ground and there was no short. We forgot to...

With the 1K resistor in-line to the motherboard, what is the voltage drop across the 1K resistor? I.e., is there +16v on the power...

So it does not sound like a diode short on the power rails then. Forgive me if I'm duplicating suggestions already tried in this thread...

Thank you both for your efforts. I've uploaded the complete version of the manual to the SWTPC section on the deramp website. Mike

Sounds like the power supplies are cycling into self protect mode over and over. A 165 ohm load at 16v is less than 1.6 watts, so a...

A while back I came by a couple original cassette tapes from SWTPC including the Co-Resident Editor/Assembler and the 2.3 version of 8K...