Sanyo 20EZ Technical question

travguy72

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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!
 
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you're the TV repair guy but I've heard bad things about not using a 100v iso xfmr... didn't blow any caps? you say the B+ pot regulates a bulb? I've had to replace a few of those pots. If you can't get it down I think you'll be in HV shutdown or something similar, I've been there. but as you mentioned i do believe you should get glow and gray screen without a signal
 
Not only do you need 100V but it also needs to be an ISOLATED circuit - even if you had a 100v wall outlet and you plugged it in there you still would have blown it up.

Unless your variac has isolating qualities (which I could it assume it may or may not), you'll need an 100v isolation transformer, which also conveniently would eliminate the variac if you buy one that takes 120V as the input.
 
a couple things you need to check and some you need to replace.

check Q901 to see if it is still good.
check ALL the resisters in the VR circuit by Q901.

replace the B+ pot if it is still that S^%$Y metal one.
replace IC601, if it is bad you will never be able to adjust your B+.
it will normally pop when plugging the monitor straight into a wall like you did.

there are many counterfeit IC601's out there.
i have some NOS 100% tested in stock.

if you need parts i have them.

shoot ma a PM or an email.

if you are local to me in VA you are welcome to bring it by the shop.

Peace
Buffett
 
I don't know if this matters, but Honestly when I do monitor repair. I 100% of the time use a Isolation Transformer if it needs it or not. I feel it is better to error on the side of caution then anything.
Also if your going to be doing several monitor repairs, I would consider building a "dual voltage" ISO.

I made one and it works great, top outlet is 100VAC and the bottom is 120VAC.
 
This monitor REQUIRES the use of an isolation transformer and operation at 100 VAC.

If the monitor has not been recapped (replacing all the electrolytic capacitors) then do so please before doing anything else or you're just chasing your tail.

Yes, this monitor should "free run" when power is applied. It also uses inverted video signal (different than all other arcade games). Nintendo had to be different.
 
Thanks for the messages guys! Yeah I knew people were gonna tell me that I had to use an isolation transformer. I am using one now a Variac set at 100v. All caps are ok, and I don't have a problem with B+ regulation. It will read higher if there is no load. (No horizontal deflection). I have used a 75w light bulb on the B+ side of the power resistor for troubleshooting many of old CRT type sets. It mimics the load of a HOT and you can make sure your B+ isn't high by using this method before you blow HOTs. My B+ is fine with a load. I can put the pot exactly at 108.

My problem is there is no drive out of IC401 but I have Vcc on pin 12. Anybody know about the vert side of IC401 and does secondary scan derived Vcc power pin 24? What need to be staisfied on IC401 to generate horiz drive? I have no hold down activated on pin 9. Help! lol
 
if you cannot adjust your B+ then chasing the problem with IC401 is a moot point.

if you must, use a bulb for a load and get your B+ stable first, then see what else is wrong.

the Sanyo is a funny chassis, if the B+ is not correct and working properly, nothing else will function properly or at all.

that is just how they are designed.

i have fixed dozens and dozens of them and the first step is the B+ always always always.

Peace
Buffett
 
I can adjust my B+. It is 108v exactly with load. It is high without load of horiz out running. If you remove the HOT of a working 20ez wouldn't B+ go high? I don't have a problem with B+ under load. It does regulate quite well with light bulb. I'm thinking I have a crack somewhere. Or I blew an obscure part that I haven't found when hooking it to 110.
 
Sorry I haven't replied but I got it working! Horiz hold pot was bad. Had a crack on pad on top of it. It would read good sometimes and then would read open. Thanks to Buffet who pointed me in right direction! I will post pictures of pot. I used a 2k pot off another monitor until I can get correct pot installed. Machine works great and was able to adjust colors and no burn in either! Looks great, and after repair of joystick plays perfect! Thanks to all who posted. Oh by the way I did run the AC up to 117 on variac just to see if it would work and regulate at line voltage and it does just FYI! The B+ is now at 108 rock solid. Will post pictures soon.
 
Thanks for the update.

glad it is fixed and looking great.

glad i could help point you in the right direction.

Peace
Buffett
 
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