Robotron monitor wake-up issue

char1ie

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When I turn on my Robotron cocktail the monitor is heavily blue and all the colours are wrong - game is fine and playable. Within a minute or two it flickers and fixes itself. Where should I start looking? Monitor cap replacement?

Thanks,


Charlie
 
I'd start with the monitor. Normally the chips in the video circuit either work or they don't. The only other (remote) possibility is that the +12V power supply may be flaking out. A bad +12V can make the video do strange things.

ken
 
Sounds like a cold solder joint. Inspect neck board and reflow solder where necessary. If the problem still persists then you need to pull the monitor chassis and reflow the header pins.
 
I took some video last night. Excuse the music in the background. You can see the video issue - screen is blue/grey where it should be black. Later it fixes itself - it takes a few minutes.

At first:


A few miutes later:



Is this a monitor issue, board issue or power issue? And the machine also reset itself last night a couple of times.

Thanks all,


Charlie
 
Last edited:
has to be a cold solder joint somewhere since it fixes itself after warming up, I'd take the board out and resolder the pins where the video hooks up and resolder the red,green,blue pots on the neckboard

Might as well cap it while its out :)
 
Check the voltages at the corners of the RAM chips. If it is resetting as well as having video issues, that usually means the power supply needs to be rebuilt.

You need to test the voltages at the RAM chips to be sure about CPU board voltages. It is not uncommon for cracks at the headers or bad filter caps to drop the voltages dramatically in the RAM chips.

Measure the voltage at the 4 corners of one of the RAM chips.
The voltages should be
Pin 1 = -5V,
Pin 8 = +12V
Pin 9 = +5V
Pin 16 = Ground
The pins are numbered starting in the upper left corner (the side with the notch), going counter clockwise. If any of them are low or are fluctuating more than 0.1 V you need to check your power supply.


ken
 
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