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Thanks Dave, This issue is getting me increasingly confused. I tried to go back to basics and follow the logic by probing the inputs and outputs...

The LOCI-2A has a failure when powered on and the NIXI tubes don't light up. We put the original 1401A NIXI board back in the machine, and all of the...

This is not how you check capacitors. Checking what voltage is across the capacitor does not verify if it's good or not, you need an LCR and/or ESR...

I think that the interrupt issue was on the PDP-12, so that behavior should be common to many of the PDP-8s.

Thanks for the comments on our blogs. We will continue to make the blogs even if we add some videos. From watching a lot of technical videos it...

Booting my TRS-80 into the CP/M disk gives me this message: "TRS-80 Model 4 64k CP/m vers 2.2 (c) (p) 1982 Digital Research Inc. Bios vers 2.22...

IMG 287 is a copy of the Atari Pong video game board IMG 294 is an epson printer board IMG 299 is an early Central Point option board Telemeter...

if you have a logic analyzer i'd take a look at what read commands it is sending. they may interleave the volumes on the physical media it's...

Interesting: mine is marked as DSM 2421 C on the outside and XC-1200U inside, but bought boards, the CRT etc. have Mitsubishi markings.

I used a 4164-15 which works fine. Interestingly it was the first chip in bank 0 that was dead and that killed the whole board. Also not having a RAM...

There are several ways you can do this much easier, than with RS-232C Transfers. I've included my TRS-80 Definitions that are for 22DISK,...

I just build the AT2XT convertor on a perfboard, and here is the circuit diagram. I am using v0.94 of the firmware. However, during post, the AT...

>>> I subsequently reprogrammed the Lattice GAL22V10B successfully to match Bob's original IOT2.jed. The trouble is that you may now have...

That's not the case, at least with 5162/70s and their faithful clones. Because IBM decided to latch the MEMCS16# signal on AEN, the ONLY way to...

I certainly hope not. The raster never really collapses like it would with a FBT failure. Just shakes a tiny bit at the edges

The thing to watch out for with 4164 DRAM is whether they are 128 or 256 cycle refresh devices. 128 cycle DRAM will work in place of 256 cycle...

Thanks Kevin, I used my TL866CS EPROM programmer to compare Jim's IOT1B.jed with the IOT1 contents and it verified good. Strangely IOT2 did not...

Buzzing out with a meter my video circuit matches the Rev 1 board, video schematic is on page 219, Fig C-18. As luck would have it, while I was...

Probably need to decode to binary....

The board labelled "Telemter Magnetics" will be some sort of core memory driver board... https://www.computer.org/profiles/erwin-tomash The...

It is unlikely the pots problem. It is more likely that the sync signal is no getting to the multivibrator. The fact that you are able to get the...

I checked the online schematics and the ICs referenced (B14 and C11) are the types as specified. There must be at least two (2) revisions of the...

Yes, if its is rolling vertically on both monitors, and won't come into vertical lock, it suggests something has happened to the vertical sync pulse...

It might or it might not stay on. With the current drain from the dummy load, this tends to store some energy in the the filter inductors and...

Hi Hugo, Thanks for the reply but you didn't read the whole message. In the first paragraph I said I'd also tried an LCD TV and my trusty Sony PVM...

Hi ... the board is a D808 and you will get documents from https://support.ts.fujitsu.com/ there you have to go to "Produkt Support" -> ...