Had an issue this weekend working on a monitor with moomootown and Flinnster that I thought was worth recording here in case it helps anyone else out trying the same thing. The original monitor was from a Blast City and had died a few months back, the issue was traced by Grant to one of the customs that is impossible to replace without a donor chassis. Luckily yanton6262 on eBay listed some Blast chassis just after the New Year and moomootown managed to grab a replacement 2933 chassis in good condition to replace the original 2931.
It seemed to work OK, the image was quite dull and slow to warm up so I did a cap kit replacement to try to improve things. It seemed to help a bit but after many hours of adjusting the settings we just couldn't get a good result. Geometry wise the image was pretty good, we had to adjust the convergence but it looked good on a test pattern, the focus was behaving oddly too, sharp in the centre and fuzzy in the corners or the other way around but tricky to find a sweet spot. In the end we reinstalled the monitor and left it for the night but I managed to find a thread over on Arcade Otaku about a guy with a similar issue although he was installing an MS2933 onto a 2930 tube. The thread mentioned a resistor in the heater circuit that needed to be changed and while there were photos, none of them showed the exact resistor position on the chassis
Not one to give up without a fight, after a bit of detective work moomootown found the offending resistor, a 3 Ohm in position R732. I had a dig in my spares box but had nothing that low but then looking at the two chassis side by side saw a resistor in the exact same position on the busted 2931 chassis, read the value and it was a 2 Ohm, just what we needed
Swapped it out and by jingo, it worked
For reference you need a 2.2 Ohm 1w fusible/flameproof fuse for this fix
2931 Chassis:
2933 Chassis:
2391 Resistor:
2933 Resistor:
The all important result:
Chunksin2019-01-28 14:22:29
It seemed to work OK, the image was quite dull and slow to warm up so I did a cap kit replacement to try to improve things. It seemed to help a bit but after many hours of adjusting the settings we just couldn't get a good result. Geometry wise the image was pretty good, we had to adjust the convergence but it looked good on a test pattern, the focus was behaving oddly too, sharp in the centre and fuzzy in the corners or the other way around but tricky to find a sweet spot. In the end we reinstalled the monitor and left it for the night but I managed to find a thread over on Arcade Otaku about a guy with a similar issue although he was installing an MS2933 onto a 2930 tube. The thread mentioned a resistor in the heater circuit that needed to be changed and while there were photos, none of them showed the exact resistor position on the chassis
For reference you need a 2.2 Ohm 1w fusible/flameproof fuse for this fix
2931 Chassis:
2933 Chassis:
2391 Resistor:
2933 Resistor:
The all important result:
Chunksin2019-01-28 14:22:29
