Hello all,
I have a Poly 800Mk1 with a display that is blank.
I have tested the 7 segment LEDs and they are working.
Tested all the power rails and they appear to be correct.
I am reading around 3000hz on the RES 7.5 pin. Getting 3MHz on the clock out of the CPU.
I am using a DVM's frequency counter to read the measurements, i do not have a scope at the moment.
I am only seeing 0.7MHz on the ALE pin of the CPU when it looks like it should be 5.5MHz.
Also I am getting no reading on the Timer out pin of the 81C55.
So that is as far as my troubleshooting has got me. There is sound coming from the Poly, but the keyboard appears to do nothing. Sounds like the plane taking off effect that precious posts have described.
Any ideas as where I should look/measure etc, as I'm stumped at the moment!
Thanks in advance for any ideas
Al