IBM 3151 - Loud Squeal and No Picture

[Trinitron]

Hello all. I have a 1988 IBM 3151 terminal that I have acquired. It has been sitting for at least a decade without being turned on. When plugged in, 9 out of 10 times, there will be a loud, high-pitched squeal when I turn on the device. That squeal will persist until the device is turned off. There is no picture, no glow, nothing to see on the front of the tube.

1 in 10 times, the squeal will occur for a second or two and then stop. A second or two after that, I get a single beep (Post?), but still no picture/glow... Nothing else happens after that.

The board looks okay as far as I can tell, nothing visibly wrong that I could see.

I would appreciate any help and/or anecdotes you may have. Thanks in advance.

 

[Hugo Holden]

Sounds like a VDU fault. You could post the VDU schematic would help and prepare to make some tests on it. For most simple VDU's the CRT's heater runs directly from the 12V supply, other times they can run from the FBT, in any case the schematic will help decide where to initially look.

 

[daver2]

Yep, locate a schematic or (better still) the technical manual.

It will be either the power supply or the high voltage generator part of the terminal.

As this is your first post, welcome to VCFED.

Don't forget you will be under moderation hir your first 10 posts.

Dave

 

[Trinitron]

I have looked and this model of terminal doesn't seem to have a schematic on the internet. I did find a reference manual for an end user but that was it. I also looked for a good picture of a motherboard and was unable to find one. Some other IBM terminal models did have schematics. Inside the 3151 is a single board with all components on it. Attached is a (poor photo) of the unit in reference. If I could find a ground point on the board, I could discharge the CRT and disconnect the board to get a better image and better look at the board. Are you able to see a ground point that I am overlooking? I wasn't sure if the screws holding the CRT to the screen housing were grounded.