20EZ -- sound, but no picture

Shoegaze

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I'm attempting to replace the problem-ridden Sanyo 20EZ in my Donkey Kong with a (supposedly "100% working") 20EZ purchased from an eBay seller. I've run into trouble, though, and I want to make sure I've ruled out any issues on my end before assuming I was sold a bum monitor.

The specific problem I'm having is that the monitor doesn't appear to be displaying any picture at all -- the monitor doesn't light up, there's no "buzz" coming from it, it's basically behaving as if unplugged. That said, the speaker IS getting power, and I can clearly hear gameplay sounds when I drop in a quarter and press start.

Checked so far:
+ Fuses are good
+ Turning up the brightness on the flyback did nothing
+ Adjustment knobs on the chassis do nothing
+ Tried different video cable, though I guess that shouldn't make a difference

Is there anything I might have fouled up when hooking up the new monitor? What should I check before assuming the worst?
 
weird, I just posted about an EZ the other day, mine had no power, but no sound either. I'm not entirely sure how that all piggybacks to the amp board, but what's the likelihood that your flyback is dead? or cold solder elsewhere?
 
A few more details after futzing with it for another hour or so:

First, the B+ is at 130v, which I understand to be "off the charts" for these monitors -- I believe 105v to 108v is what you shoot for with these, correct? B+ adjustments didn't seem to make any difference at all, it's reading 130v at both ends of the potentiometer sweep.

Second, after about 90 seconds of letting the monitor warm up to get a B+ reading, the speakers started making a noise not unlike my old RX7's rotary engine. This now persists after restarting the machine, and happens regardless of whether the sound cable is connected to the game board. Adjusting the volume pot doesn't affect the volume of the noise, but it does affect the frequency(!) of the noise.

Third, I tried hooking up the old monitor just to confirm that I hadn't somehow blown the 100v step-down transformer or something, and it works fine. Well, it works like crap, which is why I'm trying to replace it, but at least it lights up. ;)

Is this still sounding like a solder joint/flyback issue? The high B+ measurement means that I'm officially in over my head as far as diagnosing this damn thing. Any advice is pretty deeply appreciated at this point.
 
You are in HV shutdown, which is why you don't see the tube light up at all.

Measure the B+ pot through it's range. Then test D601 - D604. If all is good, replace IC901.
 
Dumb question, but where can I find IC901? I'm only seeing 201, 401, and 601.

Sorry to bump this after three months... my workshop was unusable all summer, and I'm just now getting back to work on this stuff.
 
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