Philips Computer Monitor 80

Last week I further fine-tuned my CRT repair skills by getting a Philips Computer Monitor 80 (BM7522) running again after almost a decade of inactivity. Some backstory: I found an old Commodore 128D in my mother-in-law’s basement with this original monitor. The whole setup worked perfectly for about 20 minutes, then the monitor started failing. The C128 computer is still going strong, and I’ve since substituted this monochrome monitor with a 19″ Sony Trinitron TV, a better fit for this machine given that it isn’t monochrome. Now those C64 games can shine in all their colorful glory. Recently I’ve been using the 19″ Trinitron for an interstitial diorama at bava.studio, so my attention turned back to the original monitor.

Philips Computer Monitor 80 sitting atop the Commodore 128D

I have to believe my confidence has been buttressed by all the work I’ve been doing on various G07 monitors as of late.

G07 Monitor Boy and His Trusty Arcade Assistant, Part 1

G07 Monitor Boy and His Trusty Arcade Assistant, Part 2

I seemed to remember that the Philips 80 monitor would not power on. I tested it to confirm, and the screen was black, so I thought this was going to be a quick one-and-done fix: just replace the C104 capacitor (4700 µF / 25V) for the power supply and I’d be back in yellow monochrome heaven. It’s the biggest cap on the board, so you can’t miss it.

Philips Computer Monitor 80 chassis with C104 cap highlighted

I ordered the cap from Twisty Wrist Arcade before I went to America (amongst many other  parts) so I could bring it back to Italy. After a quick swap, I noticed there were signs of life when turning it on and off; nonetheless, the screen remained black. I then had the bright idea of adjusting the brightness and realized it was turned all the way down. It dawned on me that it probably wasn’t the power supply filter cap to begin with, but I take solace in the fact that replacing 40-year-old capacitors is almost always a virtue.

Philips Computer Monitor 80 with vertical compression on the bottom half

Anyway, once the brightness was turned up, it was the same issue I had 10 years ago. At this point I turned to both Gemini and ChatGPT to see what other capacitors might be responsible (I tend to check both to see if they concur, and if not, ask why). The nice thing about ChatGPT is that I can include an image and it will immediately provide a diagnosis:

ChatGPT response to my query about other caps to replace on the Philips Computer Monitor 80 board

It is definitely chatty, but it does provide useful overviews, which I’ve been benefiting from.

ChatGPT recognizing C433 as the issue

The two capacitors in that area—C433 and C434—for which I had replacement parts were the ones I changed based on tips from ChatGPT. Once again, changing old electrolytic capacitors is rarely a bad thing on these chassis, and in this case it worked.

Capacitors C433 and C434 on the Philips Computer Monitor 80

Once I replaced those and re-installed the chassis, everything worked normally again.

Philips Computer Monitor 80 up and running in all its monochrome glory

Damn, that felt good. A piece of hardware sitting around “broken” for 10 years was brought back to life with less than a few dollars’ worth of parts. I have to say, ChatGPT cross-referenced against Gemini can be genuinely useful for these kinds of fixes. They’re by no means entirely reliable, and you have to treat them as starting points, but they’ve helped me on more than a few occasions when it comes to getting old CRTs back up and running.