Please ask questions by replying to the thread not with PMs. That way everyone gets questions answered and every one else gets to learn more.
Scope
Years ago I started off in electronics with nothing more that a volt meter. Analog at that. I now have a well stock repair shop going with some decent equipment. But took years to accumulate. Back then there was no internet to look stuff up on. No great forums like this one to go on and ask how something works, or where to find a part. Well, at least there were local places to find parts! Everything was trial and error. At least for me.
What I am hoping to do in this thread is share with you some of the tricks of radio repair. And maybe some of the other techs will jump in and add a few things. Reason I am doing this is that I get pm's and emails from cb'rs and new hams everyday asking different things about their radios. Just today I received one from the Netherlands asking about an article I wrote a few years ago on another forum.
Also by reading the forums there are many folks that are trying to repair their own radios. These are the different folks than just the ones that want plug and play. So don't worry shop owners. You loose no business with this. The plug and play operators will continue to support you
The art of radio repair is dying. Around my area there is only one other person that works on older tube stuff. And he is semi retired. There are three other shops that only repair solid state units. If you want to start off repairing your own rigs there is nothing better to start with than a CB Radio. Why?? Well it does not matter if you are a cb or ham radio operator. You have to start somewhere. CB's are cheap. You can pick them up at yard sales for a couple of bucks. So if you destroy it you are not out much and maybe a lesson learned.
Standard Shop Equipment
Here is some of the tools you will need to start repairing radios.
A good set of hand tools.
Regulated power supply.
Dummy load. (A home-brew 100 watt is fine)
Analog and digital volt meter.
25 to 45 watt soldering irons.
Solder wick
Solder sucker (Radio shack has a nice solder sucker iron. Get them while they last)
Assortment of test clips
Magnifying lamp (Well I need one)
Frequency counter
I want but can not afford shop equipment
Service Monitor
Dual trace oscilloscope
Transistor tester
Capacitor tester
Variable bench power supply
Signal tracer
The bottom list gets very expensive but are a must for professional repairs. But if you are affected by today's economy, you probably will struggle to get the stuff. And no need to take food out of the families mouth just for you to learn. So lets see if we can compromise a bit.
Service Monitor.
This is the next best thing since sliced bread. If you look around the net you can pick one up for a few hundred dollars. But the good ones are more like a few thousand bucks. I use the IRF 1200. And see them all the time for 3 to 4 grand. Take a look. You will see. But since we are starting off with cb, I will show you away you can test a radio.
The Poor Mans Service Monitor / Generator (P.M.M for short)
The poor mans monitor is nothing more than a converted cb radio. The first service monitor I ever owned was a modified cobra 23 channel radio. The radio was removed from its shell and mounted in a larger metal case. This way I could add the needed components to complete the unit.
I added a internal power supply. This does not have to be a large amp supply but needs to be stable. The driver and final of the radio will be removed. The pre-driver will deliver all the power you need to test receivers with. You will need to build an attenuator so you can vary the output in generate mode. In the one I had I used a 12 position switch with resistors added of various resistance to achieve less db output.
With today's export rigs, you can build one that will cover more frequencies and AM, CW, SSB, FM.
List of things to add to monitor
Some radio's of choice are the Cobra 25 GTL or Cobra 29 GTL (Classic). The older model. These were built tough and hold up good. So if you have an old beat up one lying around use it. One important thing to consider is you need to add some shielding to certain area’s. If you can find some very thin sheet metal you can solder it together. Double sided pc board works great also. Most of the shielded compartments will be small so it will not take much. There are several sources for this including RF Parts and Tesco.
We will start looking at the radio antenna lead. We will need to isolate the area were the TX and RX comes together at. You will need locate D8 and R39, L10, C44, and C142.
More to come
Scope
- General
- Shop equipment
- homebrew test equipment
- Basic trouble shooting
- Receiver
- Transmiter
- Phase lock loop
Years ago I started off in electronics with nothing more that a volt meter. Analog at that. I now have a well stock repair shop going with some decent equipment. But took years to accumulate. Back then there was no internet to look stuff up on. No great forums like this one to go on and ask how something works, or where to find a part. Well, at least there were local places to find parts! Everything was trial and error. At least for me.
What I am hoping to do in this thread is share with you some of the tricks of radio repair. And maybe some of the other techs will jump in and add a few things. Reason I am doing this is that I get pm's and emails from cb'rs and new hams everyday asking different things about their radios. Just today I received one from the Netherlands asking about an article I wrote a few years ago on another forum.
Also by reading the forums there are many folks that are trying to repair their own radios. These are the different folks than just the ones that want plug and play. So don't worry shop owners. You loose no business with this. The plug and play operators will continue to support you
The art of radio repair is dying. Around my area there is only one other person that works on older tube stuff. And he is semi retired. There are three other shops that only repair solid state units. If you want to start off repairing your own rigs there is nothing better to start with than a CB Radio. Why?? Well it does not matter if you are a cb or ham radio operator. You have to start somewhere. CB's are cheap. You can pick them up at yard sales for a couple of bucks. So if you destroy it you are not out much and maybe a lesson learned.
Standard Shop Equipment
Here is some of the tools you will need to start repairing radios.
A good set of hand tools.
Regulated power supply.
Dummy load. (A home-brew 100 watt is fine)
Analog and digital volt meter.
25 to 45 watt soldering irons.
Solder wick
Solder sucker (Radio shack has a nice solder sucker iron. Get them while they last)
Assortment of test clips
Magnifying lamp (Well I need one)
Frequency counter
I want but can not afford shop equipment
Service Monitor
Dual trace oscilloscope
Transistor tester
Capacitor tester
Variable bench power supply
Signal tracer
The bottom list gets very expensive but are a must for professional repairs. But if you are affected by today's economy, you probably will struggle to get the stuff. And no need to take food out of the families mouth just for you to learn. So lets see if we can compromise a bit.
Service Monitor.
This is the next best thing since sliced bread. If you look around the net you can pick one up for a few hundred dollars. But the good ones are more like a few thousand bucks. I use the IRF 1200. And see them all the time for 3 to 4 grand. Take a look. You will see. But since we are starting off with cb, I will show you away you can test a radio.
The Poor Mans Service Monitor / Generator (P.M.M for short)
The poor mans monitor is nothing more than a converted cb radio. The first service monitor I ever owned was a modified cobra 23 channel radio. The radio was removed from its shell and mounted in a larger metal case. This way I could add the needed components to complete the unit.
I added a internal power supply. This does not have to be a large amp supply but needs to be stable. The driver and final of the radio will be removed. The pre-driver will deliver all the power you need to test receivers with. You will need to build an attenuator so you can vary the output in generate mode. In the one I had I used a 12 position switch with resistors added of various resistance to achieve less db output.
With today's export rigs, you can build one that will cover more frequencies and AM, CW, SSB, FM.
List of things to add to monitor
- Internal power supply
- Dummy Load
- RF attenuator
- Tone generator
- Frequency off % meter
- Frequency counter
- On Air pick up loop
Some radio's of choice are the Cobra 25 GTL or Cobra 29 GTL (Classic). The older model. These were built tough and hold up good. So if you have an old beat up one lying around use it. One important thing to consider is you need to add some shielding to certain area’s. If you can find some very thin sheet metal you can solder it together. Double sided pc board works great also. Most of the shielded compartments will be small so it will not take much. There are several sources for this including RF Parts and Tesco.
We will start looking at the radio antenna lead. We will need to isolate the area were the TX and RX comes together at. You will need locate D8 and R39, L10, C44, and C142.
More to come
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