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Power Macintosh 5400/120 - Yellow tint on CRT?
Posted by: acfrazier on 2020-08-04 08:10:19
So I acquired this machine today from Freecycle, and the only issue I can find is it has the typical dead 4.5V clock battery which is easy enough to replace, but there's a yellow tint on the CRT that I can't seem to resolve in software. Pulling the back panel off the machine yields only one disconnected cable (shown) that I don't know what it is for. Is the tube dying, or is there some other cable/connection I can check?

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Posted by: jessenator on 2020-08-04 08:24:56
Not sure what that 10-pin ribbon is to... interesting. All the connections to video should be on the edge connector, except for the GIMO port for PC Compatibility cards and the Video In for ext AV I/O : https://wiki.preterhuman.net/Power_Macintosh_5400#/media/File😛M5400_Mere_1600.jpg

If you're feeling adventurous, there is a "Video" section in this PDF that goes over adjustments to the CRT and how deep you need to dig into the machine. http://tim.id.au/laptops/apple/legacy/powermac.perf_5400.5500.pdf

There are some small trimpots that will let you adjust certain things that you can't in software with these models.

To my eyes it seems that the "drive" per channel (RGB) are a little out of sync. But it may just be the white balance has been set funky, so go through the whole section to make sure you're not treading on your own feet, so to speak. Usually, you'd hook up a voltmeter and adjust it that way, but a visual adjustment is a decent stop-gap. As with all high voltage things, especially CRTs, perform the adjustments at your own risk.
Posted by: acfrazier on 2020-08-12 08:17:57
So, I tried making the adjustments and there was no meaningful change. I suspect there's either an internal issue somewhere or the blue gun on the CRT has died. My question is, how can I troubleshoot this further?
Posted by: techknight on 2020-08-13 03:15:43
Yea your missing the blue gun. You could try adjusting the drive control, or tapping on the CRT neck PCB to see if it comes and goes, to rule out bad solder joints. 

Could be anything. 
Posted by: Franklinstein on 2020-08-30 20:14:45
That 10-pin ribbon connector is for the TV tuner card. Don't worry about it.

The 5xxx series had a series of recalls for video problems. Unfortunately I haven't found any TIL articles regarding exactly what each fix was for, let alone the procedures involved, so I can't help much (and I have several of these things that could probably use the repairs). The repaired machines have stickers on the back case depending on which repair was performed.
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