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Heathkit H-89 no H Prompt

M

mudmin

Experienced Member
Joined
Jan 5, 2022
Messages
99
To be honest, I never thought I'd get to the point where I ever saw anything on the screen on this machine, but here we are. I have an H89 with a serial, floppy, and 16k memory expansion all hooked up. When I boot, I get the blinking cursor and the keyboard works. The screen looks good. However, I never get an H prompt. The floppy doesn't spin or try to do anything.


I'm looking for some advice about where to go next.
 
When you say "keyboard works", do you mean if your type characters they appear on the screen? In that case, you may have the "off line" button down - try pressing again to release it. This is a very common issue with H89s that have been moved around, as that key can get depressed and not noticed.
 
I've tried both. I'll start by saying that I have no clue what I'm doing on this machine. With the Off line button down, the text echoes back to the screen (as I think it should). I need to double check what it does when the key is up, but if I'm understanding correctly, I should see some sort of H or H_ prompt and I don't, which I think means the cpu board may not be working properly.
 
Yeah, sounds like something on the CPU board. There is a serial connection between the terminal and CPU boards, so maybe check that that is still connected. Then probably start the usual trouble shooting. There is an active group of Heathkit enthusiasts, so if no additional help shows up here there are other places to ask. One resource is here: https://sebhc.github.io/sebhc/documentation.html, and you should be able to get manuals and schematics there.
 
Not sure if you've dealt with this issue yet, but do you hear two beeps when you turn on the H89, or just one? I recently acquired a (mostly) working H89A, and when it's working properly, you hear two quick beeps (one from the terminal hardware, one from the Z80 board) after flipping the power switch on, and the 'H:' prompt (eventially) appears afterwards. Just figured I'd point that out.
-Adam
 
I just hear the one beep. The z80 board isn't doing anything.
 
mudmin said:
I just hear the one beep. The z80 board isn't doing anything.
Click to expand...
Have you checked to see if the voltages going to the Z80 board match those listed in the assembly manual? I believe there are some tantalum caps along the top of that board, so it'd be a good idea to check those. A webpage chronicling H89 repairs, including at least a couple of instances of tantalum cap failure, can be found here. Good luck!
-Adam
 
Sweet. Thank you. I will look that up. I wasn't getting anywhere, so I set this one to the side to let it think about its behavior. I'll see what that group has to say.
 
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