Repairing a Marconi Instruments 2955A Radio Communications Test Set, part 1


Mikko has written an article about Marconi 2955A repair:

First off, I decided to see what was the deal with the CRT. I have never worked on CRTs before, I have understanding of how the picture is formed by steering the electron beam using the deflection coils but that’s about it. I know a charged CRT can be deadly so I took my own safety very seriously. After carefully removing and inspecting the CRT drive board AC1, I noticed that someone had been there before. There were telltale signs everywhere. Screws missing, protective plastics missing, horrible soldering jobs… The CRT-to-chassis grounding strap appeared to be on but when I touched it ever so slightly, it just came off. I also noticed a TO-220 transistor (vertical deflection control) had apparently been changed by cutting off the leads from the old one and badly soldering a replacement on.

More details at Mikko’s blog.

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  1. I’m quite interested in Mikko’s progress. There are a lot of 2955’s out there (including mine) that could stand to have their CRTs retired and new LCDs installed.

  2. Hi, I have read your artical on converting the Marconi 2955A crt to other video format, perhaps LCD. Having read the parts 1 and 2 I am somewhat troubled that the artical has gone no further. I have the same problem with my 2955 which I have proved to be the flyback transformer. I to was concidering the conversion from crt to lcd or such….. However I do not have the knowledge to design a method to do this, which I was so interested in your report. I have to wonder whay you did not finish the design. There must be a few people like me who would really love to know the end result.

    Kind regards.


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