I got this chassis for a cabinet that I’m JAMMAfying. It’s the 25-29″ version of the chassis. The chassis arrived in a generic box that almost didn’t belong, and no manual or documentation of any sort.
The quality of the pcb looked ok at first glance, but then I discovered a number of issues. One high voltage capacitor was a pull complete with an old QC sticker from what appears to be the previous decade. Wires to the yoke were too thin, power plug wires were barely soldered in and seemed like no thicker than 22 gauge.
Then I couldn’t figure out whether the tube I had was correct since I had no info. Found some posts online about yoke acceptable yoke resistance:
- Horizontal – 1.3Ω to 2.5Ω
- Vertical – 6.0Ω to 12.0Ω
My tube had 1.4Ω horizontal and 4.1Ω vertical. I was worried about the vertical being way too low and blowing it. Turns out I was over reacting. Later on, I accidentally connected the horizontal yoke coil to the vertical connector and didn’t notice for a good minute. Chassis ended up surviving that.
These have a number of issues including issues with geometry, no degaussing coil, bloom artifact. They are also difficult to adjust with many knobs. Made a video about this one as well which may be useful to some.
I will list the things I did to correct the problem for each issue that I encountered. I will continue to update this page with more info as I deal with the issues one by one:
- Vertical can’t stretch all the way with max setting – replace LA7840 with LA7841 vertical driver IC
- Vertical too big at min setting – add a 1,2 or 3 ohm 5 watt resistor in series with the vertical yoke. Also downgrade to LA7840 if vertical IC is LA7841 or above
- Color smearing – turn down high voltage on the flyback but color gain up.
- Bloom during brightness change – this chassis has a huge problem with this as reported by nearly everyone. I’m currently investigating.
Will update this page with more info as I learn more.