Hi Everyone,
I've been working on repairing this beautiful CRT monitor off and on for the past several months and I'm really at a loss for what might be causing the problem.
Unlike other common Horizontal Deflection issues which result in a steady vertical line, when I turn the monitor on, there is a pulsing (somewhat segmented) vertical line. I've attached a photo that shows the issue (difficult to capture without video). The monitor itself is branded as a P225f, but it turns out that it's actually a Pf815 that has an Add-On smallish PCB that expands it to support 22 inches (the original Pf815 was only 20 inches). I confirmed this by doing some digging and found some old polish CRT forums where techs talked about this. I've also attached the service manual to this post (albeit it doesn't cover the Add-On PCB), but it's 98% accurate.
Since then I've completely disassembled the monitor, and re-flowed a large number of potentially degraded solder joins (everything around the Flyback Transformer, Horizontal Deflection Circuits, Horizontal Driver Circuits, etc.). I've also recapped 35 higher capacitance / higher voltage caps across the main PCB, and a few on the input PCB, and the Add-On PCB as well.
I also replaced the HOT (Horizontal Output Transistor), the Damper Diode, and the Chopper MOSFET (all three were *dead*). All the main IC's were also re-pasted to their respective heat-sinks (the paste was 20+ years old).
Unfortunately despite all my efforts, I still have the same symptoms. I'm hoping someone could give me a clue as to what's going on.
I've included some photos from directly after disassembly, to more recent photos that show all the caps that have been replaced (each one that was replaced has a black dot).
The service manual has very detailed schematics, here are some relevant components:
Q555: Horizontal Output Transistor (mislabeled on one schematic as Q550) *REPLACED*
D555: Damper Diode *REPLACED*
C554: S-Correction Capacitor (film cap) *NOT REPLACED*
Q881: Chopper MOSTFET *REPLACED*
T541: Horizontal Driver Transformer
T542: Horizontal Output Transformer
T601: Flyback Transformer
At this point any advice / suggestions would be very welcome. I'm at the point where I'm not sure what else I can do.
Thanks!
I've been working on repairing this beautiful CRT monitor off and on for the past several months and I'm really at a loss for what might be causing the problem.
Unlike other common Horizontal Deflection issues which result in a steady vertical line, when I turn the monitor on, there is a pulsing (somewhat segmented) vertical line. I've attached a photo that shows the issue (difficult to capture without video). The monitor itself is branded as a P225f, but it turns out that it's actually a Pf815 that has an Add-On smallish PCB that expands it to support 22 inches (the original Pf815 was only 20 inches). I confirmed this by doing some digging and found some old polish CRT forums where techs talked about this. I've also attached the service manual to this post (albeit it doesn't cover the Add-On PCB), but it's 98% accurate.
Since then I've completely disassembled the monitor, and re-flowed a large number of potentially degraded solder joins (everything around the Flyback Transformer, Horizontal Deflection Circuits, Horizontal Driver Circuits, etc.). I've also recapped 35 higher capacitance / higher voltage caps across the main PCB, and a few on the input PCB, and the Add-On PCB as well.
I also replaced the HOT (Horizontal Output Transistor), the Damper Diode, and the Chopper MOSFET (all three were *dead*). All the main IC's were also re-pasted to their respective heat-sinks (the paste was 20+ years old).
Unfortunately despite all my efforts, I still have the same symptoms. I'm hoping someone could give me a clue as to what's going on.
I've included some photos from directly after disassembly, to more recent photos that show all the caps that have been replaced (each one that was replaced has a black dot).
The service manual has very detailed schematics, here are some relevant components:
Q555: Horizontal Output Transistor (mislabeled on one schematic as Q550) *REPLACED*
D555: Damper Diode *REPLACED*
C554: S-Correction Capacitor (film cap) *NOT REPLACED*
Q881: Chopper MOSTFET *REPLACED*
T541: Horizontal Driver Transformer
T542: Horizontal Output Transformer
T601: Flyback Transformer
At this point any advice / suggestions would be very welcome. I'm at the point where I'm not sure what else I can do.
Thanks!
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