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I tried it, but it didn't charge it right - need to change out the resistor for charging -- the big 2w green one, and then you also have the timing wrong, but it's said that you can leave the battery connected for at least two months to the charger without any battery degradation (check the...

A lot of the higher priced listings nobody ever buys, they just keep listing them. I think they do that to set a price reference so when you see that one for $100 less you're like 'wow thats a great deal!', but you can check the completed sold ones to get an idea what the going rate is, and look...

I did get one, but it looks like it takes a mini din not a din, so back to square one. I might be able to wire one up with those breadboard jumper cables, at least temporarily.

Where did you test that? VRF is voltage reference for the 7508 cpu and it's just a sampling, if it's below 1.8 then it's "critical low voltage" and you get a warning. Otherwise, it should be between 1.8 and 2.x on that VRF test point. That's the input for the ADC and you can adjust that with the...

The screen should get about 20v with +15 and -5, making the 20v difference. The overvoltage protection kicks in around 7.5v so I'm sure that the power supply voltage wouldn't be causing an issue. I was seeing 6.75v from my power supply when it's connected under load and same as you about 9v...

Could you share what "doesnt look right" looks like to you? What voltages are you seeing?

I got one of these, replaced the onboard battery, hooked up into the main battery plug with my bench power supply, and I am not able to get it to show anything on the screen, other than a long horizontal line that can move down the whole screen. I went through the technical manual and so far...

Very interesting. I'm thinking this might be used to calibrate the suppository testers, not testing suppositories. That would make sense, as the person would most likely have to visit the site, so they need something portable, and test the tester to ensure it is working properly. It probably has...

The roms are connected to the address space, and normally are not relocatable due to using absolute addressing in the machine code.

I thought it was 3khz for the test tape. There's websites that sell them. Around $50 or more.

Yes, the serial port can go at 38400, but I'm interested in using the RS232C port because I have some older devices that I'd like to try connecting it to (like a Tandy Model 100).

Generally, when troubleshooting a boot issue, you want to look at three things, to start: Power, Clock, Reset. Check that the voltages are correct, check the clock is generating a valid clock, and that the reset is acting properly. Is it coming out of reset, is it activating reset? Based on what...

If it was available, I'd order one, thanks for the link.

If the batteries are good, but the ram disk isn't working, you might have some bad components in the ram disk. It's 40 years old, so well past the capacitor lifetime. Check caps, resistors, etc - verify the test points get the proper voltages.

Just an update, I can set the 'transmit character delay' to 1ms, and enable DTR, and on the HX-20 use LOAD "COM0:68N1F" and that will transfer a bit faster, though it seems slower than 4800 imho, it works.

So, I made a serial null modem cable for my HX-20, as I wanted to test if the serial port was working. It seems like it is. Here's how I did that... I basically got a DIN-8 (full size) cable (I think they sell these for midi) and cut it in the middle, then stripped the wires back and used one...

Technically, you could use one 16k rom in the expansion unit, but not three.

No, the guy who wrote it said it was assembly, and he also wrote a telecomm part to it, though I haven't found it yet. I'm not trying to do that, sorry for any confusion. https://www.vintagecomputer.net/fjkraan/comp/hx20/memoryMap.html According to this, if I set it to 24kb ram (total)...

Just tested, if I set the jumpers on the expansion unit to A,A and dip switches OFF,ON,OFF,ON then it does indeed load to the same mapping as the builtin option rom slot. That makes swapping out the software a little easier, though I cringe every time I swap a rom out when I hear the crunch. It...

You can configure the expansion unit 1 on 2 off 3 off 4 on, to get 16k additional (+ the 16k builtin gets you 32k). That disables the internal option rom port, but... you do get the 13B (at least it reads the FORTH rom and shows it as available) and maybe 14B, but otherwise, you can flip the dip...