[sebhc] H90

Carroll Waddell carrollwaddell at sc.rr.com
Thu May 10 19:30:24 CDT 2007

Does anyone have any troubleshooting experience on Heathkit H89? I 
bought 2 (neither will work) hoping to be able to repair and keep at 
least one.
I've swapped the terminal logic board with the one in my H19 terminal, 
so I know the TLB is ok. The CPU board had several blown tantalum caps, 
and I've replaced those. All the voltages check out ok with little to no 
ac ripple. With a scope, I can see activity on the address and data 
lines but I still get no display on the CRT (except the blinking 
cursor). The TLB does give 1 beep when the power is turned on. (The same 
thing my H19 does)
It's difficult to troubleshoot when the only thing visible is suppossed 
to be on the CRT screen.

I suppose it could be in the serial port interface.

Anyone else have any ideas?

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