Skip94
Member
Hi all, Hope this is ok here.
I've got an IBM 5151 monitor that is exhibiting some strange behaviour.
It partially works and shows what it should for 1/2-1 second at a time, then the picture goes crazy, before settling down again. I'm genuinely unable to describe it properly, so have taken a video and will link it below.
I'm a relative beginner with electronics, but am comfortable safely discharging the CRT and with working around the mains voltage parts of the board.
So far I have visually inspect all the capacitors, had an initial look for bad solder joints and reflowed a few that I wasn't happy with. I have also tested the diodes in circuit. Just to check they have a voltage drop one way and nothing the other, I haven't actually check the specs. One seemed to test bad in circuit, so I desoldered it, but it then tested fine off the board, so I refitted it. This has made exactly zero improvement.
I have tested this on at least two different 5150's with different MDA/MGA cards. All of the PCs and cards work perfectly with my other 5151.
Has anyone come across a similar problem? I could just crack on and start randomly swapping components out, but I'm hoping someone may be able to point me to a specific area to start looking.
Cheers
Andrew
I've got an IBM 5151 monitor that is exhibiting some strange behaviour.
It partially works and shows what it should for 1/2-1 second at a time, then the picture goes crazy, before settling down again. I'm genuinely unable to describe it properly, so have taken a video and will link it below.
I'm a relative beginner with electronics, but am comfortable safely discharging the CRT and with working around the mains voltage parts of the board.
So far I have visually inspect all the capacitors, had an initial look for bad solder joints and reflowed a few that I wasn't happy with. I have also tested the diodes in circuit. Just to check they have a voltage drop one way and nothing the other, I haven't actually check the specs. One seemed to test bad in circuit, so I desoldered it, but it then tested fine off the board, so I refitted it. This has made exactly zero improvement.
I have tested this on at least two different 5150's with different MDA/MGA cards. All of the PCs and cards work perfectly with my other 5151.
Has anyone come across a similar problem? I could just crack on and start randomly swapping components out, but I'm hoping someone may be able to point me to a specific area to start looking.
Cheers
Andrew