Trying to figure out 2 problems with IBM G74 Black Monitor and G40 Monitor

[TheGeneralLee86]

I am in need of some help of what is going on with these 2 rare Monitors a IBM G40 CRT and Black IBM G74 Monitor.

The IBM G40 CRT Monitor symptoms is won't power on at all when I push button nothing happens

The Black IBM G74 turns on normally but there is no Video or OSD but I do hear the degaussing when it turns on and who I bought it from said it was working completely, but it was shipped to me and it was an open box brand new old stock one. I do hear it click once kind of louder then my other G74 that is beige colored. I also do not hear or feel static on the front when I turn it on. It does not click till a few seconds or so after it degausses on startup. I also have pictures of it which i will post.

[TheGeneralLee86]

Re: Trying to figure out 2 problems with IBM G74 Black Monitor and G40 Monitor

Here is a couple and the rest are in the zip file because it would a pain to upload them individually.

[RJARRRPCGP]

Re: Trying to figure out 2 problems with IBM G74 Black Monitor and G40 Monitor

Welcome! Cool to see that it's a CRT!

Unfortunately, I left all my CRTs behind in 2016, despite I had one that was like brand spankin' new!

[TheGeneralLee86]

Re: Trying to figure out 2 problems with IBM G74 Black Monitor and G40 Monitor

Mine are all for my Vintage Computers to play retro Games on original Hardware. I really want to fix them both because I believe they are both rare and Hard to find ones.

[sndestroy]

Re: Trying to figure out 2 problems with IBM G74 Black Monitor and G40 Monitor

If you have HV and degauss on the G74 but no image, check for CRT heater voltage (and associated circuitry). Should be close to 6.3 VAC.

edit. hhmm, if there's no static when turning on, then HV is not present. You need to check that 1st.

[momaka]

Re: Trying to figure out 2 problems with IBM G74 Black Monitor and G40 Monitor

I can't quite tell from the posted/attached pictures which monitor we are looking at: the G40 or the G74?

If I had to guess, looks like it's the G74?? Either way, the "CM2300" chassis lead to this service manual:

...
which is basically a Philips 107s.

Not sure if that appears to be the correct service manual for your monitor. So you will unfortunately have to download it and verify if your boards match the ones in the SM. I suggest starting with the power supply. See if the fuse, bridge rectifier/diodes, and other input components' designators and values match the ones in the SM. If not, this might not be the right monitor.

That aside, even without the SM, my suggestion would be to start by looking for bad solder joints on the board, as that is the most common issue when a monitor is shipped and doesn't work afterwards. Especially check the larger components or anything that is mounted to a heatsink, as those are most prone to cracking their joints. Probably also a good idea to provide pictures of the underside of the board too so that we can double-check.

Do the same for the G40 too. In fact, since the G40 doesn't seem to power ON... after checking for bad solder joints (and if it all looks OK), check mains fuse. If fuse is OK, plug monitor in and check that you get about 160V DC (or 320V DC in countries with 220-240V AC mains) on the big input cap. If that's there, look for any 78xx regulators on the board (usually 3-terminal devices in TO-220 package), and see if they are getting a voltage on their input and output pins, and measure what that voltage is. One of these should be for a 5V standby rail, which should always be present as long as the monitor is turned ON.

And that's about all the advice I can think of right now, given the info above.