Hoping someone can help me with the CRT

[kclements]

Hello everyone!

I am trying to get a IFR 1600 Communications Service Monitor up and running.

I have ran into a strange problem with the CRT that I have never seen before.

The CRT only appears to have a 2" picture in the center of the screen. Everything on the outside edges is missing.

When I first powered it on this is how the picture was. The next time I powered it up to my surprise the picture looked near perfect. As I was getting familiar with the unit going through the menus , the red all of the sudden disappeared but it still had a full picture. I turned it off for the day. The next day I came back and powered it up and the picture looked great again. As I was using it, it decides to drop the green this time but still had full picture.

After that every time I power it on it has looked the same. Just a partial logo from the main screen in white.

I have another monitor that is a different tube/chassis that is pretty warn out but displays a full picture. I used it to check the video card output to make sure it wasn't a problem with the video card.

The first picture is what the monitor is doing right now.
The second picture is reference of what the screen should look like (using the warn out monitor)


Any help would be appreciated.

Regards,

Kevin

[ARC Tech-109]

First congrats on finding a *working* IFR monitor, this coming from a retired Motorola 2-way tech. All of the FMAM series of IFR monitors are known for weak and often temperamental display sections thus the reason for the plasma used in the COM120.
The monitor section is similar to what was used in the 90's vintage ATM's and POS equipment, the problem is without a service manual or direct knowledge this is going to be one of those seat-of-the-pants repair projects that requires a lot of general electronics experience. That being said I would compare the various voltages between the monitors and use this to narrow down the problem, my money is on a bad pass regulator transistor and some leaky capacitors that are loading things down.

Does yours have the CGA/VGA port on the back for an external monitor? This was an option for them and it might be a better way in the long run

[kclements]

Hello ARC TECH-109,

Thanks for the reply.

I have 2 IFR-1600's . Both of them have issues. One of them has a bad Processor board. That is the one I "barrowed" the CRT from to test the other IFR-1600 I have. The CRT's in them are from 2 completely different manufactures. So the board layout is not the same between them. I think the CRT tubes are even different .

Unfortunately neither of mine have the "monitor" out option on the back.

I have attached the schematic and board layout information for the monitor that has the issues.

If you get a chance can you look them over and give me a an idea of where to start looking?

Regards,

Kevin

[ARC Tech-109]

First look at the +12v coming in the monitor section at the end of C46 with a scope looking for ripple, from there check the output of the DC-DC converter as everything else rides on this, being a switching supply the filter caps are suspectable to ESR losses.

JQO? SQO

[ARC Tech-109]

https://www.repeater-builder.com/tes...lex-index.html

There's a big section on the IFR 1600 service monitor