Amiga 1080 Monitor

[mrtropicguy]

I was replacing some capacitors on my Amiga 1080 monitor and when I finished I noticed that picture color was all off.  I tried adjusting the colors based on information from the service manual, but can't see to get it to produce a white image.  I've attached my test image and the image that gets produced on the monitor when using the composite input.  Anyone have any suggestions?  Is is just a matter if getting the colors tuned correctly or could there be something else wrong?

[spaceman88]

I was replacing some capacitors on my Amiga 1080 monitor and when I finished I noticed that picture color was all off.  I tried adjusting the colors based on information from the service manual, but can't see to get it to produce a white image.  I've attached my test image and the image that gets produced on the monitor when using the composite input.  Anyone have any suggestions?  Is is just a matter if getting the colors tuned correctly or could there be something else wrong?

Did you adjust the grey scale? Turn the colour control all the way down (B/W), turn the brightness down to a modest level and adjust the red, green and blue controls (on the CRT board or on the back of the main board) until you have a screen with no colour tint, true B/W image. Then try turning the colour back on.

[JimS]

Did you check the capacitors you changed? (Assuming they're not simply in the power supply.) Bad solder joints.. bridges... electrolytics in backwards? What does the RGB look like?

[mrtropicguy]

Did you adjust the grey scale? Turn the colour control all the way down (B/W), turn the brightness down to a modest level and adjust the red, green and blue controls (on the CRT board or on the back of the main board) until you have a screen with no colour tint, true B/W image. Then try turning the colour back on.

Can I just use the RGB color bar image I have been using for this adjustment?  Like the one I attached to the post?

[mrtropicguy]

Did you check the capacitors you changed? (Assuming they're not simply in the power supply.) Bad solder joints.. bridges... electrolytics in backwards? What does the RGB look like?

Yes.  I double check the capacitor values, checked the polarity, and I've looked at the soldiering under magnification.  It all seems okay.  I've even gone so far as to change out the video processor chip on main board.  But I always get the same results -- a screen with no white.

[spaceman88]

Can I just use the RGB color bar image I have been using for this adjustment?  Like the one I attached to the post?

Yes you can, but looking at your picture again, your white bar is completely black. That's not a grey scale adjustment. Not sure I've seen this before.

[mrtropicguy]

Yes you can, but looking at your picture again, your white bar is completely black. That's not a grey scale adjustment. Not sure I've seen this before.

It's strange.  You think if you can see each individual color then showing white would be easy since it's just the sum of the parts.  I'll double check all my work again.  Maybe I missed something.  The  monitor was fine until I changed the capacitors.  I still have the old ones.  Maybe I'll switch them back.

[spaceman88]

It's strange.  You think if you can see each individual color then showing white would be easy since it's just the sum of the parts.  I'll double check all my work again.  Maybe I missed something.  The  monitor was fine until I changed the capacitors.  I still have the old ones.  Maybe I'll switch them back.

If you replaced with the proper ones you shouldn't have to change back. Check to make sure you didn't hit a service switch somewhere, I'm not sure what this monitor has, but some have switches to kill vertical sweep, kill colour (for the grey scale I mentioned) etc., seems a long shot but...... Also as someone mentioned, poor solder joints around the CRT board and on the wires that run from the main board up to the CRT board.

[mrtropicguy]

If you replaced with the proper ones you shouldn't have to change back. Check to make sure you didn't hit a service switch somewhere, I'm not sure what this monitor has, but some have switches to kill vertical sweep, kill colour (for the grey scale I mentioned) etc., seems a long shot but...... Also as someone mentioned, poor solder joints around the CRT board and on the wires that run from the main board up to the CRT board.

There is a service switch that will kill the vertical sweep.  I used that when I attempted to perform the white balance calibration in the service manual, but I got stuck on step 10 when I couldn't make adjustments for white.

1. Set the switch (S201) to COMP.
2. Connect the monitor to a white pattern signal of composite.
3. Set the COLOR control to minimum.
4. Turn the SCREEN control (on T461) fully counter clockwise.
5. Set the service switch at SERVICE.
6. Turn the RGB CUTOFF controls (R556, R558, R559) to obtain each CRT cathode voltage (KR, KG, KB) will be 100V DC using a high impedance voltmeter.
7. Slowly turn the SCREEN control clockwise until any two horizontal color bars appear.
8. Turn the CUTOFF controls counterclockwise so that two horizontal color bars of RGB (in the statement 7) disappear.
9.  Turn the SCREEN control clockwise again until the third horizontal color bar appears.
10. Adjust the first and second color CUTOFF controls so that the horizontal color bar will be white.
11. If the white horizontal bar is glittering, turn the SCREEN control counterclockwise until the bar glitters slightly.

I'll double check the neck board connections and solider joints.  Thanks for the help.

[mrtropicguy]

I'll leave this here in case anyone has a similar problem....

My problem was a caused by three broken/intermittent solider joints on the P115 connector that connects the video board to the drive board.  To find the issue I sent a white image on the composite input.  Then I started pushing on the connectors with and insulated probe.  I noticed a flash of white on screen so I probed further until I found the intermittent connection.  I attached a photo of the bad joint.  I removed and replaced the soldier on every pin for this connector and the monitor has been rock solid since.

[mindprober]

Excellent work! I would not dare go near the inside of a CRT.

[spaceman88]

Excellent work! I would not dare go near the inside of a CRT.

The dangers of CRT's have been greatly exaggerated over the years. A microwave oven is far more dangerous, I met a guy who lost 2 or 3 fingers because he did the test for high voltage incorrectly (to say the least).

[mindprober]

I wouldn't go inside a microwave over either! :roflmao:

The dangers of CRT's have been greatly exaggerated over the years. A microwave oven is far more dangerous, I met a guy who lost 2 or 3 fingers because he did the test for high voltage incorrectly (to say the least).

[spaceman88]

I wouldn't go inside a microwave over either! :roflmao:

Well, better safe than sorry :-).

[JimS]

I'll leave this here in case anyone has a similar problem....

I've seen a number of 1084s develop bad solder joints on the flyback transformer. I think it's a combination of heat and the 15kHz vibrations from the transformer. Not so much on the 1080s. I don't know if they are more reliable, or if there are just fewer of them. :-)