travguy72
New member
Hello all, new here but been a tv repairman (they still have those lol) for 28 years but just recently got into fixing some arcades for myself from my misspent youth. I am stumped right now on this monitor. This is from a non working Donkey Kong that I recently purchased. Here is what I have done:
I noticed 300ma fuse was blowing and flyback was bad (oozing) HOT became shorted. I replaced with flyback (I bought two and have swapped both), HOT, fuse, and a good cap kit from Victor @ Arcade Parts and Repair which included the audio board as well. I didn't know it at first it required 100vAC ONLY but I didn't have it plugged to anything, plugged directly in outlet and monitor came on. I had good regulation of B+ (108v), and turning up G2 revealed nice full raster. I let it play for a few minutes and then it went out, no fuses bad. Fired it up again after unplugging it and this time tapped on PCB and it went out. I then resoldered entire board but it never came back on. I then researched and put a 100v Variac on it and here is what I have now:
I have replaced IC401 la1464 even though I have read it rarely fails. So must not be bad as same issue. B+ will regulate with an external load (light bulb) but is running at 129 without. Vcc is going to pin 12 of IC401 but no horiz out waveform on pin 10. Pin 9 hold down is at 0, and I have tried lifting pin 9 as well no change. No cracks on board that I can find (I have spent days looking).
My questions are: This monitor should free run without any signal applied as soon as 100vAC applied correct? Doesn't the vertical side of IC401 pin24 come from secondary via Flyback? What starts the horiz out on pin 10 and what has to be present for it to happen?
Thank you and I've always wanted a Donkey Kong as it used to kick my ass every time I played it! HAHA! I've successfully rebuilt a Ms Pacman and I was always pretty good at it and it is my favorite video game. Glad to be a member I can tell I've got the bug and will be restoring others as soon as I can!
I noticed 300ma fuse was blowing and flyback was bad (oozing) HOT became shorted. I replaced with flyback (I bought two and have swapped both), HOT, fuse, and a good cap kit from Victor @ Arcade Parts and Repair which included the audio board as well. I didn't know it at first it required 100vAC ONLY but I didn't have it plugged to anything, plugged directly in outlet and monitor came on. I had good regulation of B+ (108v), and turning up G2 revealed nice full raster. I let it play for a few minutes and then it went out, no fuses bad. Fired it up again after unplugging it and this time tapped on PCB and it went out. I then resoldered entire board but it never came back on. I then researched and put a 100v Variac on it and here is what I have now:
I have replaced IC401 la1464 even though I have read it rarely fails. So must not be bad as same issue. B+ will regulate with an external load (light bulb) but is running at 129 without. Vcc is going to pin 12 of IC401 but no horiz out waveform on pin 10. Pin 9 hold down is at 0, and I have tried lifting pin 9 as well no change. No cracks on board that I can find (I have spent days looking).
My questions are: This monitor should free run without any signal applied as soon as 100vAC applied correct? Doesn't the vertical side of IC401 pin24 come from secondary via Flyback? What starts the horiz out on pin 10 and what has to be present for it to happen?
Thank you and I've always wanted a Donkey Kong as it used to kick my ass every time I played it! HAHA! I've successfully rebuilt a Ms Pacman and I was always pretty good at it and it is my favorite video game. Glad to be a member I can tell I've got the bug and will be restoring others as soon as I can!
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