I put two Sony Trinitrons on the bench, one from 1986 and one from 1976, to see if they worked and whether the older set could be repaired. The 80s set was a hot pink Sony KV-1397R with front controls, a headphone jack, RF and AV inputs on the back, and a manufacture date of November 1986. The 70s set was a heavier analog model from October 1976 with VHF and UHF tuners, dual earphone jacks, and only antenna connections.
The 1986 TV came up right away. I hooked up an NES over RF on channel 3, got a solid picture, and then adjusted the front panel controls because the hue was pushed all the way over, brightness was maxed out, and picture was turned down. Once I centered those controls, Super Mario Bros. looked sharp and the set sounded good. I also checked the erase and add buttons and found that they manually removed or restored channels in memory.
The 1976 set did not go nearly as smoothly. I connected an Atari 2600 through a balun to the antenna terminals and powered it up, but I only got hum with no high voltage and no picture. That meant opening it up and seeing what was going on inside.
With the chassis exposed, I looked over the layout and dropped the serviceable board down for access. The set was full of dust, and I cleaned old flux residue from the power board with IPA so I could inspect the solder side more clearly. I checked the mains fuse first, but it was good, so I started working through components on the power section.
After a lot of testing, I found a bad regulator transistor mounted to the chassis and ordered a replacement. I also compared notes with a long repair from shango066 covering nearly the same Sony set, and that lined up with what I was seeing. Along with the regulator, I found a failed horizontal device, several bad resistors in the same area, and one hot carbon resistor that broke apart when removed, so I replaced those parts as well.
The first power-up after that went badly because I had left a wire against grounded metal and shorted the circuit, which blew the fuse. Once I got past that, I measured 166 volts where I expected 148 volts feeding the regulator, and the output was too high as a result. I brought in my friend Jim, and together we cleaned a potentiometer I hadn’t fully tested and added a light bulb as a load so the supply would regulate properly. With that setup in place, the circuit settled to about 115 volts.
That still wasn’t the end of it. A horizontal centering pot got extremely hot and smoked, so I replaced it with a new high-wattage unit. I also swapped the burned 1 watt replacements for larger resistors, but when I reconnected the flyback and CRT wiring, the resistors near the flyback smoked again almost immediately. I did get a brief bit of audio, but the set never came up.
The 1986 Trinitron worked fine after adjustment and cleanup. The 1976 set never made it back, and I stopped the repair after repeated smoking around the flyback circuit.
— Aaron
Links
Timestamps
00:00 – Intro
00:32 – 80s TV First Look
04:29 – 80s TV Testing
08:59 – 70s TV First Look
13:24 – 70s TV Testing
15:10 – Inside Layout
19:34 – Repair Attempt
32:06 – Smoke
41:14 – Wrap Up