Help resurrect my Xerox Alto

Exceellent. And you realise that the most important piece of equipment for repairing something is not electronic, it's a brain :-). No problem/. That, surely, is one thing the classiccmp list is for. Exchanging repair/diagnostic tips, etc. While not its only use (and nor should it be), it's certain;y a very important use for the lsit. Anyway, I've had another look at the monitor info on bitsavers. It appears it's a Ball Brothers monitor, and the information is a reprint of the original service manual for the monitor (makes sense). There's a fairly good secion in that manual on diagnosing faults. If you have that monitor (and it's not certain, Xerox may well have used other manufacturer's monitors -- the PERQ, for example, may have had a VMI, KME, Moniterm or 3 rivers monitor depending on the model!), yuo want to look at the that manual carefully. Firstly, the horizontal fdeflection system, which as usual, produces the high voltages for the CRt, wil lrun without sync pulses. So you should get HV without the Alto doing anything. Secondly, the mains PSU prodcues 2 votlages. One is the 6.3V AC supplky to the CRT heater (which implies the heater will be alight even if just about anything else has failed). The other is regulated down to 55V and suppleis the monitor electronics. The manual suggests you measure this first since if there is a short or overload, the regulator circuit will shut down. IIt then suggests isolating the verticla and horizontal defleciton circuits by removing connetors (details are in the manual) to see what is fialing. If you have that model of monitor, I can see no reason not to follow that procedure... -tony