691
CB Radio Repair Forum / Re: R27 receiver
« on: March 14, 2014, 09:06:39 AM »
After replacing R11 a 47K I now see 31 MHz
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692
CB Radio Repair Forum / Re: R27 receiver
« on: March 14, 2014, 09:05:34 AM »
Cleaned the sockets and no change. So decided to drag out the Sencore CS61 scope and take a few measurments. Seems that the Tek scope loaded the signal paths down. But the Sencore did the job. What I did was probe the output of bother oscilators, the 5 MHz and the 31 MHz where they combined. All I could see was the 5 MHz side as noted in below screen shots.
693
Home Brew And Tech Forum / Re: Icon718 SWR meter
« on: March 02, 2014, 08:01:35 AM »
Have you tried a full reset on this radio?
Reason I ask is that there is really not a lot of seperate stuff between the swr and rest of the metering circuit
Reason I ask is that there is really not a lot of seperate stuff between the swr and rest of the metering circuit
694
Test Equipment / Re: Com Ser Laboratories tear down possible repair
« on: February 24, 2014, 05:04:12 PM »
Here is the scope CRT. was hoping to find some match on the internet but google returns only a few.
695
Test Equipment / Com Ser Laboratories tear down possible repair
« on: February 23, 2014, 09:16:34 AM »
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#new
The 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.
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#new
The 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.
696
Manuals / Re: Com Ser Lab BR1000a Service monitor schematics
« on: February 22, 2014, 03:48:26 PM »
scope board
697
Manuals / Re: Com Ser Lab BR1000a Service monitor schematics
« on: February 22, 2014, 09:00:39 AM »
Even more
698
Manuals / Re: Com Ser Lab BR1000a Service monitor schematics
« on: February 22, 2014, 08:58:27 AM »
and more
699
Manuals / Re: Com Ser Lab BR1000a Service monitor schematics
« on: February 22, 2014, 08:56:47 AM »
more
700
Manuals / Re: Com Ser Lab BR1000a Service monitor schematics
« on: February 22, 2014, 08:53:24 AM »
Here are some tear down pics
701
Home Brew And Tech Forum / Re: Icon718 SWR meter
« on: February 17, 2014, 04:37:16 PM »
Hey Jerry,
I will pull the schematic one night this week and look over that SWR circuit.
Two things. It is missing the signal or the adjustment pot could be bad that calibrates the circuit.
I know you have a scope so this may be a good test to learn what is going on by using that scope.
I will have to reseach that mic issue.
I will pull the schematic one night this week and look over that SWR circuit.
Two things. It is missing the signal or the adjustment pot could be bad that calibrates the circuit.
I know you have a scope so this may be a good test to learn what is going on by using that scope.
I will have to reseach that mic issue.
702
CB Radio Repair Forum / Re: Cobra 2000 restore
« on: February 17, 2014, 04:33:42 PM »
I had gotten ahold of some like that also. Pulled my hair out trying to figure what was wrong with the thing
703
New member welcome / Re: New Guy Here
« on: February 16, 2014, 10:07:00 AM »
Welcome to my little piece of the web Jerry. It is great having you here.
Sounds like you have a lot of fun on radio. I only work on them and very seldom get the time to chat anymore. But hey, working on them is fun.
Sounds like you have a lot of fun on radio. I only work on them and very seldom get the time to chat anymore. But hey, working on them is fun.
704
CB Radio Repair Forum / Cobra 2000 restore
« on: November 29, 2013, 03:17:48 PM »
Time to bring new life in an old radio
705
Signal Generators / Sencore CB42 manuals
« on: November 24, 2013, 06:45:01 PM »
In this thread I will start a repair series for the Cb42
The bottom manual has the color schematics.
The bottom manual has the color schematics.