Toshiba Rear Projection Convergence board problem

Don't adjust the convergence until you repair the convergence circuitry. It will be way out of wack, when you later realize it was bad in the first place. Replace the STK...-...convergence IC's. The resistor is propably blown again. Also check all the low ohmage resistors. After repairing the convergence, you can "tweak" it if need be. Sky.

Thanks, I'll replace those STK ICs... I wasn't sure if it was actually not adjusting, or if it was trying to adjust and there was just a problem with the board. I did test all of the low ohm resistors, and the one I replaced is the only one that was bad... and it hasn't blown again yet, but it's also higher wattage than the other was.

Pat

Hi Pat,

This is a special 15-24Khz (CGA-EGA) Toshiba Monitor built for Video Arcade Games I looked long and hard in our company archives and files for the schematics but it looks like Toshiba never gave out copies when we purchased these.

Toshiba 50" Rear Projector Engine Model No:P-R502L

PCBs VIDEO/CONV PB6101 HOZ/FLY PB6105 CONV-OUT PB6112-1 POWER PB6106

IC Information Sanyo STK392-020 3-channel convergence correction amplifier (2pcs per monitor) HOD Tr 1MB12-140 INSULATED GATE BIPOLAR TRANSISTOR Fuji Electric

To enter convergence mode.

Note: You need to have a working Game Raster input first

1/- Switch front panel convergence switch to on

2/- Press and hold TEST button for 5 seconds until convergence screen is up

3/- MODE switches between - Center Convergence - Line Convergence - Point Convergence

4/- the four POSITION keys select what to adjust in Line & Point Convergence Modes

5/- the four ADJUST keys will move the current selected Convergence Mode

6/- the three keys R, G & B select and toggle on/off each color

7/- SELECT will switch between Game Raster input and Convergence Test

8/- NEVER-EVER press the RESET key.. all stored convergence data will be deleted from memory and you will have a horrible time just to get the screen all squared up again.

9/- The WRITING key writes the current convergence data to memory. Do this often as any power glitch can exit you from convergence mode and you will loose all current settings you have made.

Convergence Tips

1/- Use Green as your base color.

2/- Square up the green grid

3/- use the point convergence to make all the vertical and horizontal lines straight as possible.

4/- For Red & Blue, first use Center convergence to converge the center

of the screen, Red-to-Green & Blue-to-Green.

5/- Then Square up each color to match the green, Red-to-Green & Blue-o- Green.

6/- Finally use Point Convergence to get best overall convergence, Red- to-Green & Blue-to-Green.

Your photos look like all the convergence data has be reset or lost so you have a long job in front of you. I don't think that the convergence amps are bad as all three guns are giving similar shaped pictures. Bad Convergence amps usually show up as one or two colors badly or unevenly distorted.

I start with Green only and use black electrical tape across the monitor front evenly spaced to the number of vertical and horizontal grid lines. Start with the horizontal first then the vertical. Once you have a good green square grid, then adjust the other colors to match.

Wes.

Wes,

Thanks a lot, that helps a TON! I pulled the board out to check for the STK ICs, and I noticed that there aren't any on this board (it's all discrete transistors). So just for fun, I started testing the resistors again, and I noticed that the resistor I pulled was supposed to be a 0.2 ohm, and I replaced it with a 2 ohm >_