Hi, it's nice to find this forum .. it's very hard to find information about CRT repair these days.
I am learning to repair CRT's and a Commodore 1902A / 1080 / Magnavox CM8505 is my first patient.
I obtained both schematics and service manual, and I have several CRT / TV repair books, but none specifically mention the issue I am seeing.
https://gona.mactar.hu/Commodore/monitor/schematics/Commodore_1084S-P_Monitor.pdfThere is no display, just a black screen.
Brightness all the way up, still black. No lines, no dots.
I can feel static electricity on the screen when I rub my hand across it.
When it turn the monitor off, there is a click and a short white flash on the screen as it goes off.
Audio works fine.
I see three orange glows (gun heaters?) in the neck.
I checked the voltage at the output transistors and I see around 100V on the collector, and 11V on the base. Emitter to Collector is not shorted.
While checking these transistors my probe bumped the emitter one time, and I saw some red activity on the screen... which made me feel like the CRT is good.
I examined the circuit board and replaced some capacitors. I see no damage or bulging capacitors. I do see some work has been done to the flyback traces.
At this point I have some guesses:
1) Voltage from Flyback is too high or too low.
2) B+ from power supply is dead.. but if this were true there would be no static electricity feeling on the screen correct?
Based on your experience where should I check first?
I'm not going any further until my isolation transformer arrives.
Should I purchase a high voltage probe? I don't think the tube voltage is adjustable.. I dont see a sub brightness or anything in this monitor.
Thanks!!
