454A Repair


Oscar Anderson
 

Greetings,

I recently acquired a "parts or not working" 454A from eBay for cheap. Turns out it's a bit of a basketcase, but I'd like to get it up and running if I can. Someone else replaced the fan (by hacking a generic 120 V fan onto the back) and tried to replace some filter capacitors. I don't know if they ever got it working after that.

When I got it, the +75 V rail was reading +108 V, and I traced this back to a short in the power supply created by the previous cap replacement. Now all of the power supply voltages measure within spec (or at least close).

I still have no trace. When I push the beam finder, even with the intensity set to maximum I get just a severely defocused line down the middle of the CRT, which cannot be focused using the focus control. It is also extremely dim, only visible with the lights off, even with the intensity pot maxed out. I did open up the HV compartment and I seem to be getting the +12 kV and ~ -2 kV that I should.

Any suggestions?


Oscar Anderson
 

I should note that the "line" (it's pretty fuzzy for a line) is vertical.


 

Verify that the horizontal sweep is working.

— Jeff Dutky