Nanao KZ-20EN-D monitor problem

[Kevin Mullins]

After scouring the net for any information, I'm hoping to find some help here. . . .

I aquired an older Data East cabinet that uses the Nanao KZ-20EN-D monitor, with a chassis board number KB240331B. This cab was in the process of being converted to a standard jamma cab due to the Data East stuff was a wreck. During this process the monitor was powered up using a 120v outlet after the game pcb and harness were mocked up..... obviously a bad idea, considering these are 100v monitor chassis. When I started on attempting to repair this chassis I assumed it would be in the power supply/ voltage regulator or something. Now I'm just confused, and have found very little on this one.

Symptom: If the chassis hasn't been turned on for a while it will turn on then after a couple seconds turn right back off. The more times you try, the quicker it will turn off. Eventually just not doing anything at all unless you let it sit awhile. There is high voltage noise from the initial turn on though. None after, and no picture.

After testing all transistors and finding none to read bad, I had read about the voltage regulator not always showing to be bad, but is. So I replaced it, along with EVERY transistor on the chassis and even tried IC401 (x-ray protect, etc).  To no avail.

Also noting the time and heat related factors from when it would attept to turn on, I cooled the board and it would remain on a little longer but with only a non-adjustable bright white screen and then turn off once again.

When it turns off you can hear a faint "tick" or "click" sound. I narrowed this sound down to the area of the flyback. Pulled the flyback and inspected for cracks, but do not see any.

I have also read about a cap on the neck board that may cause the bright white screen. But not sure if this is related to my problem.

Keeping in mind that this monitor worked beatifully before being plugged into the 120v outlet. (duh) And now has left me baffled thinking this should be an obvious fix.

Any help or insite would greatly be appreciated.

[Ken Layton]

The Nanao expert is here at:
www.jomac.net.au/mon.htm

[Kevin Mullins]

Thanks Ken . . . .

I had found Jomac's web site, defineately the man to talk to about the Nanao monitors, but wasn't sure if he'd appreciate a direct technical question at his business e-mail.  And I don't have an account with Startech Journal, so I figured I'd give a try here. I had noticed that he posted here from time to time.

Thanks again for the info . . . .

[Ken Layton]

Jomac is a member here on this forum, but he doesn't check in much. He welcomes questions at his business email. Remember that Star Tech Journal is a private business located on the east coast of the USA and is in no way affiliated with or connected to Jomac's company in Australia. That link on his site to StarTech Journal is merely so if a person wanted to join Star Tech they could if they wanted to pony up the money.

[Kevin Mullins]

Problem FIXED !!! 

More to come on the details when I get a chance to write it up.

Many thanks go out to Joey from JOMAC for sticking it out with me to the end.

[xefned]

Do you remember how you fixed this? I'm have the same issues.

[Kevin Mullins]

Wow, I hadn't been on here in a while and just happened to see this...didn't realize I never updated it.
I'll did around for my emails and notes and get back to ya.

[Kevin Mullins]

Was your monitor damaged the same way mine was? (120v power versus the 100v it's supposed to get.)

I'll start off with some general notes and then go into what eventually fixed it.

Monitor appears to be going into x-ray or over voltage shutdown.

Check C527 , C526 , C523 , C906 
Also check R525 , it's a fusible 4.7 ohm resistor could be open.

Check transistors for shorts -
Q901 (2SC2555)
Q902 (2SA1091) is a typical failure
Not as common is Q903 or Q904 (2SC2482)

Measure voltage at the 1amp fuse , it should be below 110vdc , if higher there is a problem in the power supply circuit.

After going through all of that (testing and replacing) and really finding nothing wrong with any of it....here is what FIXED mine.

R526 (100K Ohm) found open (it is next to FR525) - It was out of spec, but isn't really even a necessary part, monitor will run without it, but I replaced it anyways.

THIS IS WHAT WAS CAUSING MY HIGH VOLTAGE ISSUES -

VR910 – B+ Potentiometer (BAD)

I had a perfect 3k Ohm between A and B.   Nothing between A and C or B and C. (C leads to Q904)

    A ------
               >
               < ----- C
               >
    B ------
 
Replaced that potentiometer and the monitor fired right up beautifully.