Sanyo EZ20 Brightness

bigjohn

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I've searched, but cannot find a similar problem here.

I just recapped the Sanyo EZ20 in my Punchout machine, and when I re-installed the chassis and fired it up all the colors are washed out. It appears to be too bright, so I turned down the Brightness on the control board all the way counterclockwise. This made a very slight improvement, but the screen was still way too white. I went to the flyback and adjusted the Screen control. I could make the problem worse by turning it clockwise, but it did not seem to get better even with this control turned completely counterclockwise.

Any ideas where I should start looking? Also, is there a procedure, or proper order, for adjusting the color controls?
 
The sub brightness pot is on the chassis, adjust that as well. Reflow all your transistors on the chassis and neck board, and the pots as well.
 
try this.

center you brightness and sub contrast pots.

adjust your screen nob on the fly back till the raster lines go away. and you have a good black background.

then adjust your sub brightness pot. till you have a good black background.

then adjust your brightness pot to the desired level.

Peace
Buffett
 
If you still have probs check with member "peerless". He was able to bring my EZ20 back to life!
 
If it's not an adjustment issue.....check diodes D201, D302, D303......and transistors TR301, TR302.

Edward
 
try this.

center you brightness and sub contrast pots.

adjust your screen nob on the fly back till the raster lines go away. and you have a good black background.

then adjust your sub brightness pot. till you have a good black background.

then adjust your brightness pot to the desired level.

Peace
Buffett

What do you mean by "sub contrast pot"?

I followed your other instructions and made significant improvements, but the background has a definitely blue tint, and I am getting a slight green bloom in the center of the screen.
 
in the center of the chassis there is a pot.

sometimes it sticks straight up and some times it points toward the rite side of the board.

that is your sub brightness pot adjust it second after the fly then the normal brightness pot on the remote board.

you may need to get the tube checked with a rejuvinator.

Peace
Buffett
 
in the center of the chassis there is a pot.

sometimes it sticks straight up and some times it points toward the rite side of the board.

that is your sub brightness pot adjust it second after the fly then the normal brightness pot on the remote board.

you may need to get the tube checked with a rejuvinator.

Peace
Buffett

That is the same as the sub brightness pot? Isn't it? Sorry for all the questions, but I want to make sure that I'm not missing something.
 
the sanyo has 3 brightness adjustments.

1. the screen knob on the fly.

2. the sub brightness pot in the center of the chassis.

3. the normal brightness pot on the remote board.


to balance the sanyo correctly you must:

1. center pots #2 and #3 first.

2. adjust your screen knob on the fly.

3. adjust the the sub brightness pot in the center of the chassis.

4. fine tune to your liking with the normal brightness pot on the remote board.

hope this helps you get it looking good.

Peace
Buffett
 
I'm still struggling with this monitor.

I tried the method described by Buffett, but with the SUB-BRIGHTNESS pot set at mid-range, I get an out-of-focus image with wide, black, horizontal bars. If I turn down the SUB-BRIGHTNESS then the picture will come into focus, but the screen still appears very bright.

The only settings I found that would render an identifiable picture was with the SUB-BRIGHTNESS pot all the way down (fully counterclockwise), the SCREEN adjustment very low (counterclockwise), and the BRIGHTNESS control low to mid-range. Even with these settings the screen appears very bright.

I could not find a setting that would give me a true black background.

I've got 2 other problems that I need to address also, there is foldover on the top inch of the dispay and the picture does not fill the screen horizontally.

I have removed the chassis again to verify C407 along with the other cap. connections. What else should I cover? Re-flow all pots?

Can the horizontal size be adjusted?
 
Check and make sure you "service" switch on the chassis in in the normal setting. It's on the chassis near the sub brightness pot.
 
Followup/Resolution.

I played with, researched, and thought about this project off and on for a few weeks.

I tried doing some more adjustment and finally got to a point where the game was tolerable, but I could never get rid of the blue background.

I did some experimenting (switched video inputs to eliminate problem with video proms, adjusted blue drive on "bad" monitor) and could not eliminate or even change the blue.

Finally decided to focus on the neckboard. Reflowed the transistors and adjustment pots. On closer inspection, noticed that R257 was loose. Re-soldered the resistor. Fired it up and bingo.

Everything looks perfect now.
 
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