When I quit the commercial 2 way radio business (EF Johnson) I started doing more radio repair at home in the early 90’s. I was in need of a service monitor to generate and receive signals from and to the radio under test. I found this service monitor local and purchased it. The range is 0 to 999 MHz. Just what I needed. And with the scope and trouble tracer add on I was able to check CTCSS by watching the Lissajous patterns on the scope.
After a couple of years the magic smoke rolled out of the scope unit. A quick tear down revealed one of the PIO caps had exploded. 0.1uf @ 2kv. Being so busy at the time I simply unplugged the unit and continued to work. I think it was 7 years later the unit started showing its age. The signal out became distorted and had low output. This was time to start trying to obtain info on this unit. So off on the internet I went only to find nothing. Google search would not return anything on this unit. The only name branded part in the machine was the RF attenuator made by WaveTek. So I looked them up and ordered the precision resistors that were in the unit. The guy I talked to said that Com Ser Laboratories was sort of a fly by Night Company and was bought out by another company. Never did find out who that was.
Later in December of 2007 a friend of mine that travels found a guy out west that had the same unit less the scope attachment. He was able to scan the schematics to Adobe and emailed them to me. These looked like they had already been scanned many times and really did not have much info on them. No part numbers or part locations. So if anyone has any other info on this please let me know.
I have placed the files on my website back then for download:
http://gokarters.com/smf/index.php?topic=1736.new#newThe monitor as it looks:
Cover removed showing the rear of the unit. Here we can see the card tray that holds the boards. These use old style card edge connectors
This is a view from the top showing card tray and between the tray and front panel is the mother board.
The first card is the 10 MHz crystal oscillator board.
Here we have the card tray lifted up. It is hinged along with the mother board also.
On the bottom of the chassis you can see the power supply. This supplies:
5VDC
-5VDC
10 VDC
15VDC
-28VDC
Here is a closer look at the power supply board
This image shows how the card tray pivots to allow service to the bottom of the chassis.
Also in the bottom lef you can see the bras cylinder. this is the WaveTek RF attenuator.
I am afraid this may be a problem. The display shows the digits, although it has no power applied. If I can fix the unit I will have to come up with a new display.
This is the scope unit. It mounts on top of the generator. I am guessing the engineering department knew nothing of heat transfer back then. The main scope board mounts component side down. So a lot of heat has been transferred to the circuit board and has chard the board.
Just a closer image of the scope board.
This will most likely be a tough repair, so will be working on it in spare time. First thing I want to do is check out the power supply and make sure everything there is up to spec.
Thought I share a bit here.
