Arkanoid II monitor <model> keeps blowing fuse F902

[clhug]

I’ve got an Arkanoid II, Revenge of Doh game.  It worked fine for several years, then one day the monitor was just dead.  The game itself is still fine, I can put coins in and press the player start button and I can hear the game playing.  It’s just the monitor that’s dead.

I can’t find a specific model number on the monitor.  The tube and chassis both have stickers on them that say Sega  Part No 200-0037.  The circuit board says NANAO with the number KB240331B (or maybe that’s the leter “i” instead of the number one”).  Attached are pics.

It didn’t take me too long to find that fuse F902 was blown.  I got replacement fuses, but it blows again instantly when powered up.  I’m using 800 mA fuses there.  That’s what I took out of it.

What can I look at?

I have a basic understanding of electronics and can solder and desolder, but know nothing about monitors specifically.

I am also not opposed to just buying a replacement monitor but not sure where.  I’ve found several old references that lead to web pages that either no longer exist or no longer seem to stock CRT monitors.  Can I trust one if I find one off ebay?  I also found a post that more recent Wells Gardner monitors are not to be trusted.  What other brands are there that I could still buy, new or used?

Thank you!

[grantspain]

my good god that is a very early nanao chassis
f902 will be the b+ voltage,that fuse can blow if the horizontal output transistor is shorted or the regulator circuit has a short

model is a sega/nanao mc-2000-s i believe

[clhug]

I appreciate the reply.  Can you provide any hints on how I track down which specific components on the board to look at?  As I said, I have no knowledge specifically of monitors.  I know what a transistor, resistor, capacitor, etc. are, and how to measure them, but I don't know where to start on the board to find which ones might actually be bad.

I did track down a manual for the monitor based on the model # you gave, and see the circuit schematic, but I'm not sure what part of that diagram I should be looking at.  I do see F902 in the circuit.

[grantspain]

well unless you are quite experienced with electronics and using a meter then you will be just guessing whats wrong

when i repair chassis i isolate the flyback by removing the solder to the b+ pin,i then add a dummy load (mains lightbulb across that trace and ground) and then i go about proving/repairing the power supply circuit,once that is done i move onto the deflection circuit

the two transistors you need to read are both bolted to the heatshield of the flyback,looks like the regulator is clipped and the HOT is bolted,you will need to check each of those using a diode test

you could look putting a replacement wei ya chassis on the tube,you will need to check but i think that is a high impedance yoke,120vac isolated supply,10 pin neck,20" tube

[clhug]

No, I don't have any experience troubleshooting electronic circuits in detail, and don't know anything specifically about monitors.  But I am a computer person and overall techie and I do know how to use a meter and can solder and desolder.  If given direction on what to check I'm sure I can work through it, but I would need detailed direction, like specific components to check, and approx location on the board to look for it.

I found this manual at this web site: http://www.arcade-museum.com/manuals/manuals_monitors.php
Looking at the Nanao Sega 20" Color MC-2000-S manual.  I don't know if this is the exact same monitor, but the board layout on page 21 (but it's labeled in the scan as page 32) looks just like my board.

On the board (the real one, not just the layout in the manual) I see 3 transistors bolted to various shields.  They're listed at Q401, up on the shield of the flyback, Q402 on a small shield just up and to the left of the fuse F902 that keeps blowing, and Q901 on the right side.

I also just noticed in looking at it again, which I had not noticed before, that there's a resistor, R527, in the top right right under the flyback shield, that's charred.

I guess one other question, do I need to be removing components from the board to test them, or can I test them still soldered into the board?