The restoration process continued:

Electronic Repairs Continued:

Monitor High Voltage Power Supply:

Okay, now I've calmed down a bit after another failed attempt to power up and play the game. I had to consider the possibilities. At this point, it could be a failure of the high-voltage power supply. That said, the only other things that could prevent the picture from appearing would be either bad wires going to the CRT neck socket, a bad socket, or finally a bad CRT. I jumped back into the schematics and also read everything I could find pertaining to the high-voltage power supply. Initial power-on testing showed that none of the HV outputs were working. There's supposed to be a +90VDC output, a +400VDC output, and a 16 kV output for the CRT anode. The +90V output was running at +5V, obviously a little low.

Probing components with an ohmmeter (no power applied) revealed a shorted capacitor in the +90V rectifier circuit. See the little yellow cap sitting between the blue disk shaped cap and the large brown electrolytic cap? That's the one. Actually, the original caps in the positions now occupied by the yellow one and the blue one were both yellow colored axial cylindrical parts standing on end. One was rated 200V and the other 400V. My replacements are rated for 400V and 1000V respectively and are made of better materials, are smaller and actually fit into the PCB better.

While considering replacement of the shorted capacitor, I decided once again to go with the shotgun approach and replace as many components in the HVS as I could. I spent another whole day sourcing equivelent components available at Digikey and placed my order. When my box of parts arrived, I went to work. The result, a clean rebuilt HVS assembly. (Go to the replacement parts list for HV supply)

Again, more than 90% of the components seen in the photos below are brand new. I had to keep a couple of the original diodes because I couldn't source new equivelents. Note the large plastic housing behind the heatsink. That is where the magic happens. Inside that shell is a high-voltage multiplier circuit and custom transformer. It is completely potted internally so there is no way to repair it if something goes wrong with it. My biggest fear was that the universe would play another mean joke on me by making sure that this unrepairable section had something wrong with it. My pessimism was unnecessary in this case because later it proved to work after all.

 

Continue to Star Castle page 5 of 8, the new CRT

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