Newbie help

[timlad75]

Hi, and thanks for taking the time to read this. I've just bought a Sega Naomi arcade machine. It's a Virtua Tennis machine but I itend to strip it out and install a Mame system. I bought it knowing it wasn't in full working order. I have narrowed it down to an electrical problem as there is no power going to the monitor. I've changed the fuse and put a new one in but it keeps blowing the new fuses. But I don't know where to look next to fix this problem, does anybody have any experience with this or know what the problem could be? Many thanks

[jennifer]

      Most likely its a bad chassis or the tube is shot, (shorting).... Jennifer would take a really close look @ the flyback looking for signs of arcing (be careful though, random and unprredicable voltages may be present even after unplugging the power)

[mgb]

yep, very likely a blown flyback and a shorted Horizontal Output Transistor.

[grantspain]

what model is it,it should be either a nanao ms2932 or a sanwa es31s

is it the fuse on the monitor chassis itself blowing?

[timlad75]

the monitor is a hantarex Polostar, ive tried uploading a couple of pictures but cant figure out how to upload them yet

[grantspain]

polostar are free ac range chassis that can sync from 15khz to 38khz,they are a  robust bit of kit
for the chassis fuse to blow then you would be looking at a fault in the degauss circuit or primary ac circuit,the chassis is switch mode therefore any fault on the deflection circuit or the flyback would result in over current protection kicking in rather than a blown fuse
this is not a standard monitor for naomi cabs,they were all sanwa 29es31s or nanao 2932

I have worked on many of these chassis

btw you can run these chassis directly from any AC source from 95 to 265v

where are you based btw?

[timlad75]

Thanks for all the info it is very much appreciated. I'm from Doncaster in the UK

[grantspain]

yep that's a polostar alright

so which fuse is blowing?

I run a arcade repair company in kent btw

[timlad75]

yep that's a polostar alright

so which fuse is blowing?

I run a arcade repair company in kent btw

It's the fuse just on the left of the blue and pink wires

[grantspain]

for that fuse to blow then either you have a fault on the degauss circuit or the ntc component has shorted
you can try disconnecting the degauss coil from the chassis (its the two pin connector to the left of the power in)

[timlad75]

for that fuse to blow then either you have a fault on the degauss circuit or the ntc component has shorted
you can try disconnecting the degauss coil from the chassis (its the two pin connector to the left of the power in)

that's brilliant thank you very much for the help. im at work at the moment but will have a look as soon as I get home.