Sanwa PM1723D blowing fuse

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Sanwa PM1723D blowing fuse

Post by spikehead »

After several months I fired up my capcom cute with a Sanwa PM1723D monitor and a Toshiba tube. Two minutes in when I hit the service button the screen faded to black within a few seconds. After switching the cab off and on the monitor was completely dead (no buzzing sound, no glow, nothing on screen).
I unplugged the monitor and hooked up a VGA monitor. Everything worked fine including the service button. I checked the PSU (replaced about a year ago) and it is fine too. Upon closer inspection the fuse right next to the AC connection on the monitor was blown. The second fuse at the back of the monitor has continuity. There is no visible damage on the board.

I put in a new fuse (4A; 125 Volt) which blew immediately after turning the cab on. Again the monitor seemed to be completely dead (no buzz etc.)

I have no clue when it comes to repairing monitors. Are there some obvious pointers to look out for? I checked the repair guide in this forum but didn´t want to disassemble the monitor yet. Finding technicians who still deal with CRTs is rather difficult in my neck of the woods (northern Germany).

I included schematics for a PM1723C and a stock photo of the C variant of the board below. Thanks for your help.
7AEDE079-7F51-4A7E-B903-E96360D457EE (1).jpeg
7AEDE079-7F51-4A7E-B903-E96360D457EE (1).jpeg (171 KiB) Viewed 60 times
mon86.jpg (95.92 KiB) Viewed 60 times
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Re: Sanwa PM1723D blowing fuse

Post by grantspain »

mains fuse blowing would point towards the following
ptc, diode in bridge rectifier circuit, regulation transistor
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