What would cause both Horizontal and Vertical Deflection to Stop Working?

[Witchboard]

Still working on that G07 CAO board.

[Ken Layton]

I believe the CAO accepts positive sync signals only.

As to no hor/vert deflection, you may have lost power to the integrated circuit or a coupling or filter cap was in backwards. Always remember that sometimes a brand new capacitor could be bad right out of the package.

[Witchboard]

Positive sync only eh?  I didn't know there was a difference.  So, I'll need to find a game that outputs positive sync to get the monitor working.

[dabone]

7404 Ic Sync inverter.




pin 1 on the 7404 - sync FROM game
pin 2 on the 7404 - sync TO the monitor
pin 7 on the 7404 - Ground
pin 14 on the 7404 - +5


Boom, negative sync input.

Later,
dabone

[Witchboard]

Boom, negative sync input.

Do you mean, "BOOM, positive sync input?"  I'll google the 7404 IC.  Thanks for the heads up.

[Ken Layton]

That 7404 sync inverter trick is an old Star Tech Journal article and it's often reprinted in the Romstar conversion kit manuals like Black Tiger and Sky Shark.

[dabone]

It inverts the sync you give it, so negative sync from the game/jpac/avga/whatever becomes positive sync for your monitor.




Later,
dabone

[Witchboard]

Thanks guys.

[Ken Layton]

Yup, a 7404 or 74LS04 is a hex inverter chip. Very common part.

[Witchboard]

Yeah, cheap too. ^_^  Thanks again guys.

[Witchboard]

Hmmm.. that's not good.  I setup the chip on the monitor the way I read the description and flipped on the game.  Looked the same to me, so I turned the horizontal hold one way, then back thinking maybe I just needed to tweak something.  Then, the screen went dark... and didn't come back on.  I could hear the high pitch of the monitor, but it looked like the heaters went out.  This chassis is a nightmare.    Next time I see a CAO chassis, I'm leaving it where it lay.

[Ken Layton]

Hmmm....maybe at this point you should just order that Wei-ya replacement chassis for Electrohomes from Alva Amusements.

[Witchboard]

I'm not one to give up.  I just need a break from that particular chassis.  I did check out Alva, but couldn't figure out which chassis I would need for replacement.  I'm presuming the 820H or 814S.  I'll keep them in mind, but it just kills me for this thing to get the best of me. 

[Ken Layton]

The 820H is the one to order for your monitor.

[Witchboard]

Thanks Ken.  I'll look at that as a last resort.  I feel the more I work at this the more I learn.  First thing I'll do is maybe take the chip back out and see if the picture comes back.  Maybe I burnt up the chip?  Who knows.  Maybe the thing just finally died.  The tube isn't the best and I'm not sure if I want to drop $$ on a new replacement chassis for it.  I have more time than money at the moment.    Thanks again for all the help.  If I get the thing figured out I'll post up the results.