Atari Paperboy: replacing a Disco monitor with an Hitachi

baritonomarc

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Atari Paperboy: replacing a Disco monitor with an Hitachi

Hi all,

I am trying to figure out how to replace my "beyond any doubt" dead med res AGM20M Disco with a "no manual nor info available anywhere" Hitachi GMK-20P monitor.

Having not the manual for the Hitachi, just to avoid to readily burn it, I am assuming that being Japanese it works with 100 V and not 120V like the Disco. The second precautionary assumption is that it probably needs an iso transformer.

Now, the idea is to reduce the 130 V going to the disco monitor (coming from the original Paperboy power supply) to 100 V with a step down transformer I have by hand, so no probs for this.

(image of the 130-100V transformer)
sam1029slim.jpg


For what concerns the isolation: is the Paperboy transformer an iso or do I
need to place a, third, "big and heavy metal block" iso transformer?

Another point is the possibility to take the 100 V directly from the Paperboy power-block. Reading at the schematics package supplement, page 4 at J3 connector I can see "violet wires 100V" are declared … what it refers to?

Thanks!
 
Last edited:
Ok, i think that i have some info i can share :)

the pinout of the video connector for the Hitachi is:

1 2 3 4 5 6
V H GND B G R

About the sync, the H is composite so it was not necessary to connect the V signal (Paperboy handles the negative composite signal, brown cable from the video PCB).

I used the 130V coming from the Paperboy PSU block (once juicing the original disco monitor) just connecting it to the 0V-120V input of the transformer obtaining 110 V (not 100, but i suppose i am in the tollerance range) on the secondary winding side (yellow wires). Having the primary winding isolated from the secondary, it is a iso transformer.

Now the monitor is working and I can concentrate my efforts on the faulty PCB ;)
 
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