Hi folks,
anybody here have experience repairing the Tektronix 4500 series of desktop graphics computers? I've got a 4502 here that seemingly resets in 1sec intervals, with repeated clicking from the speaker and flickerin BUSY light. The screen glows uniformly green, but nothing else. Totally unresponsive. Nada.
A scope showed bus activity, but also in a repeating pattern, with the signal briefly collapsing in time to the speaker click. The supply lines check out ok, as far as I can tell without a service manual. Anybody got one?
Thanks for any hints,
--Roland