Picked up a free Sega Turbo upright cabinet in pretty rough shape. Worked my way through the power supply boards and then moved the CRT. On initial power up, had no neck glow, so I removed the tube/chassis from the cabinet and over to the work bench. To start, I re-capped it with a cap kit from Arcaderapiarparts dot com. Then crawled through the board testing each transistor, out of board by hand, only finding a failure at Q902 (A1091). Reflowed all the connectors, flyback, and tube socket. After a final inspection for cold solder joints, broken traces, etc, I felt good enough to power it up for another test. Set the variac/isolation transformer to 100AC and powered it up.
The tube turned on nice and after adjusting the contrast there were bright retrace lines. Connected a BK 1249 NTSC (Tested working on alt screen) generator to the R,G,B,GND,SYNC inputs and was able to lock the scrolling lines but cant seem to get any image. (See image below). Adjusting the V/H positioning/Hold knobs effect the image but its always gray lines.

Focusing in on the video amplification section of the board, Q107 controls the base leads on the video amp transistors, and seemed like a good place to start. The Transistor looked good but the wiper arms on the video bias pot (RV104) were missing and reading open.
Went back to test all the trip pots, and any of the "V8K4-1" style were bad. Ended up replacing 4x 5K trim pots used for Color gain adjust in the video amp section and 1x 3K trim pot for Power Drive in the High Voltage section. I set them to middle position and figured I could adjust from there.
On initial power up, the set was emitting a high pitch whine and had bright white bars flashing across the screen. You could almost hear an audible click each time the screen flashed. Adjusting the "Screen" knob on the flyback helped a little. Looking around online, a few folks said the B+ voltage for this monitor should be around 105v. Using the test point near fuse F902, I adjusted the (new)R910 trim pot up till the meter read 107 volts. The whine subsided and the screen settled. If I tune it any lower and the screen goes crazy again and the high pitch whine comes back. If I adjust the Video Bias to high the screen goes crazy. Adjusting the Vertical/ Horizontal knob let me fill the screen, making me think IC401 (Video Sync IC) is fine.

I'm a novice at best when it comes to CRT repair and enjoying learning as I go, as such, I'm not sure if the problem I'm having is still the video input/output section or is it something in the Horizontal/Vertical section of the PCB. If anyone has any ideas or suggestion please pass them my way.
The tube turned on nice and after adjusting the contrast there were bright retrace lines. Connected a BK 1249 NTSC (Tested working on alt screen) generator to the R,G,B,GND,SYNC inputs and was able to lock the scrolling lines but cant seem to get any image. (See image below). Adjusting the V/H positioning/Hold knobs effect the image but its always gray lines.

Focusing in on the video amplification section of the board, Q107 controls the base leads on the video amp transistors, and seemed like a good place to start. The Transistor looked good but the wiper arms on the video bias pot (RV104) were missing and reading open.
Went back to test all the trip pots, and any of the "V8K4-1" style were bad. Ended up replacing 4x 5K trim pots used for Color gain adjust in the video amp section and 1x 3K trim pot for Power Drive in the High Voltage section. I set them to middle position and figured I could adjust from there.
On initial power up, the set was emitting a high pitch whine and had bright white bars flashing across the screen. You could almost hear an audible click each time the screen flashed. Adjusting the "Screen" knob on the flyback helped a little. Looking around online, a few folks said the B+ voltage for this monitor should be around 105v. Using the test point near fuse F902, I adjusted the (new)R910 trim pot up till the meter read 107 volts. The whine subsided and the screen settled. If I tune it any lower and the screen goes crazy again and the high pitch whine comes back. If I adjust the Video Bias to high the screen goes crazy. Adjusting the Vertical/ Horizontal knob let me fill the screen, making me think IC401 (Video Sync IC) is fine.

I'm a novice at best when it comes to CRT repair and enjoying learning as I go, as such, I'm not sure if the problem I'm having is still the video input/output section or is it something in the Horizontal/Vertical section of the PCB. If anyone has any ideas or suggestion please pass them my way.


