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The Resurrection of a Broken 5175


Experienced Member
Jan 26, 2019
Texas, USA
I recently picked up this IBM 5175 monitor from Computer Reset for a mere $10. I couldn't believe my luck, but unfourtunately when I got home and plugged it in, I was greeted with the telltale sound of vented CRT arcing.



After some research and some careful consideration, I noticed that the tube in one of my 5154s looked pretty much identical, with a very similar part number. So, another trip to Computer Reset brought back a 5154 that had a smashed outer case, but a good tube.

After removing both tubes, I compared the differences. The tube out of the 5175 was a glossy tube, and was pretty similar in appearance to the tube from a 5153. It was also heavier, as it had a much thicker safety glass on the face of the tube than the tube from the 5154.
Here's a picture of what a normal 5175 looks like:

The 5154 tube is matte, and is quite a bit lighter. However, the shadowmasks appear identical, and so do the neck connectors and the electron guns.
After reassembling the 5175 with the 5154 tube, I noticed something: due to the face of the 5175 tube being a thicker glass than the 5154 tube, it left a large gap between the tube and the screen bezel. After further examination of my other 5154, I noticed that the 5175 has two sets of rubber isolators: one on each side of the mounting ears on the CRT. However, due to the thinner front, the 5154 tube removes the front set of rubber isolators to move the face of the CRT closer to the bezel. I then removed the front set of rubber washers, and the tube now sits flat in the bezel!

When I powered the monitor up to test the new tube, I was granted with an image! The color balance was quite off towards the red side, but I was mainly excited to see it display an image at all!

I then tried it in graphics mode with the windows logo:

Unfortunately, shortly after plugging the thing in, the line filter caps smoked, as all of them always do.

Being the idiot that I am, though, I thought it would be fine to plug in the PSU from one of my 5154s to test it some more. The PSUs look identical from the outside, and even have all the plugs in the same places! Unfortunately, the pinout is completely different, so it ended up smoking a trace on the board. :oops:

However, a little time at the rework station yielded what I would like to think of as a passable repair:

The special thing about the 5175 is that it is an analog monitor. It is identical in almost every way phisically to a 5154, but it is completely electrically different. The original interface used seperate analog RGB channels, and combined the H and V sync on one composite sync pin. This is normally a bummer, because it means you can't just feed VGA into it. However, in the late 80's, when the PGC was long obsolete, computer retailers started slightly modifying the video circuitry to accept seperate H and V sync, and installed a VGA cable on them. My 5175 just happens to be one of those modified versions, so it runs great in 640x480 VGA!

By some miracle, this did not damage anything other than the trace, and the monitor was not permanently harmed.
I took this opportunity to replace every single cap in the monitor, and now it functions wonderfully! After some slight adjustments to the HV, sync, and color balance sections, it displays good as new!

And that pretty much sums up my 5175 adventure! I thought I'd share it with you guys since it's a very dramatic tale of failures and success... no, I really just wanted to show off my 5175 monitor. :D

Key points to take in from this story:
1. 5175 and 5154 tubes are functionally interchangeable
2. 5175 and 5154 PSUs are NOT interchangeable
3. Don't plug in your 5175 or 5154 without changing the power line filter caps first, unless you fancy your monitor doing its best impression of a jumbo smoke bomb.

Thanks for reading, and I hope this post comes in handy to someone else with a 5175!
Thinking about it, I wonder why IBM even bothered with the EGA in the first place when the EGA and PGC used the same tubes. I believe even VGA is compatible with the PGC too.