EV-9031 Monitor Repair Part 1


My first computer was an Apple II that I bought with money I earned from working at Baskin Robbins back in 1980. It was my first experience with computers and was very early on in life of personal computers, exciting times. I didn't get a degree in Computer Science, mine was in Physics but I ended up spending my career in software development and devops. Even 40 years later it is an amazing computer, it allows you to understand computer architecture at a base level. It is also a very sentimental for me since it launched a lifetime of learning on software and hardware.

Unfortunately, I ended up selling the Apple II I had back in 2006 but I've reacquired an Apple II+ off ebay along with a 9 inch monitor like I had back in the 80s. The Apple II+ worked well right off the bat except the safety capacitor burned up, I got a recap kit for the power supply from Apple II power supply capacitor kit. It was still having issues so I went ahead and got a complete modern replacement Apple II replacement power supply, now everything works well on the Apple II.

The Monitor is from Taiwan and is period accurate for the Apple II, in fact it is very close if not the exact monitor I had back then. These green screen monochrome monitors were fairly cheap and worked well. The model number is EV-9031 but I've had no luck in finding a service manual for this model.

The initial issue I had was that I could not sync to the video at all. I thought this might be because the monitor could be a PAL version and not NTSC, this was because it had a euro style plug. I didn't have anything else to test the composite output of the Apple II at the time, so I went on the assumption that the electrolytic capacitors had gone bad. I did not see swelling, but there was some residue on the PCB and using an ESR (equivalent series resistance) meter some were showing out of spec.

So I went about replacing the electrolytics, I started with the larger ones on the power supply but ended up replacing them all. Here is the full list in case someone has the same monitor:

  1. C605 100uf 35v
  2. C310 2200uf 16v
  3. C604 3300uf 25v
  4. C417 1000uf 16v
  5. C314 1000uf 16v
  6. C102 10uf 16v
  7. C104 10uf 16v
  8. C105 10uf 16v
  9. C107 10uf 16v
  10. C503 1uf 160v
  11. C409 2.2uf 50v
  12. C411 220uf 16v
  13. C401 2.2uf 50v
  14. C406 4.7uf 16v
  15. C305 4.7uf 16v
  16. C254 10uf 16v
  17. C607 220uf 16v
  18. C202 470uf 10v
  19. C418 220uf 16v
  20. C313 100uf 16v
  21. C307 10uf 16v
  22. C311 47uf 16v
  23. C501 10uf 16v
  24. C502 10uf 100v
  25. C204 22uf 10v (near J203)
  26. C210 22uf 100v (on pcb connected to CRT)

I also replace the vertical deflection IC at the same time. The result was better but not perfect as seen below.