NANAO MS8 Fault

[vandale]

Hi all, I have a MS8 NANAO from an astro city cab, was working fine but over a short period of the time picture started to fade and now there is no pic at all. I was using it as a backup monitor when I was working on other screens.

I have looked over the board and there are no dry joints or swollen/leaky caps.

When powered on you can hear the high pitched frequency squeal that these monitors give out, sorry not sure what that is called. The neck does not glow though. I have tried adjusting the brightness, contrast and LOPT gain, still nothing.

I am thinking its the LOPT which I think you all call the flyback? What can I do to test this?

Any help is appreciated.
Thanks

[vandale]

Well I made some progress.
I have 2 identical boards, 1 as mentioned above, the other blows fuses when powered on.

I decided to tackle the fuse issue first. I found the HOT was shorted when removed from the board and tested with a multi meter. I used the HOT off the other board that tested fine on the bench. Replaced the fuses also. Reinstalled in chassis and tested. This time it powered up but the 2 smaller transistors that sit on a small heatsink went up in smoke, I am thinking this was the cause of the shorted HOT originally.

Any ideas?

Was thinking next step would be to put the HOT back on the board that has power and no smoke and take the LOPT off the smoking board.

I read online that you can simply test the LOPT by measuring the high voltage side tot he chassis and if it isn't shorted then its fine, is this correct?

Thanks
Gene

Thanks

[grantspain]

what are the transistor numbers you refer to,component position number I mean

never seen a flyback faulty on ms8 or ms9

you can isolate the flyback from the circuit to check the power supply voltages,simply desolder the b+ pin of the flyback and add a dummy load(30 watt light bulb) across the circuit board pad of that pin and chassis earth

[tolias3]

Can you post some images??