BK 2040 technical help?

[Radio Tech]

Nice set-up.......does it make a difference vtvm vs a dmm?

I prefere a VTVM over a DMM any day. That is when it comes to radio work. the vtvm does not load down the circuit like most meters would. Now for logic and microcontrollers you cant beat a DMM for that. Each tool has it;s place and certain needs. Why I have probably 70k tied up in test equipment.

 

[Eastside]

Would not run a cb shop without my trusty ole 1801. That is the best counter for cb repair. Somewhere in my arsenal of data I have a preamp for that counter. You build the pre-amp in a small metal box and use a BNC connector with a 3 inch coax added to it. Couiple the 5 volts to the counter jack and pick it off at the pre-amp. Get the end 1/2 inch from an oscilator and it picks it up. makes for a quick test to see what is running.

I have several counters but use the 1801 more then any.

Kenny sounds like you got a decent deal. the counter will bring 50 bucks no problem Seem the 1040 go for 100 to 150,. so you can say you have 100 bucks for the 2040. The price I pay for non working units.




I have 2 of those scopes. Plus 4 others including a Digital storage scope. I love 2235. Good scope.

That would be great to have......I have tried to stick my probe from the 1801 next to the oscilator and nothing....does the cb-42 have a 455k setting?

 

[Eastside]

I prefere a VTVM over a DMM any day. That is when it comes to radio work. the vtvm does not load down the circuit like most meters would. Now for logic and microcontrollers you cant beat a DMM for that. Each tool has it;s place and certain needs. Why I have probably 70k tied up in test equipment.

Thanks again......I have mostly old tube radios....so a vtvm is on my list.

 

[Radio Tech]

Ok Kenny,
I gave you the wrong cap identifier. It is C371 not C317. My mind plays those tricks at time. Part of getting old.
You should see 14.33 volts on the pos side of C317.
That is a 10uf 16 volt tantalam capacitor.

Now the above should really jump out at you.
The supply voltage to that circuit is 15 volts. I have seen anywhere from 14.5 to 16 volt on that line. This is a tantalum cap rated at 16 volts. It is most likely very stressed and these type caps fail quite often.

 

[Radio Tech]

That would be great to have......I have tried to stick my probe from the 1801 next to the oscilator and nothing....does the cb-42 have a 455k setting?

That is one of the nice features of the CB-42. not only does it have 455 Kh but it has 3.75 Kh to 12 MHz continuous tuning at 0-30-100%mod.

Looks like this forum is due for a shop talk / test equipment thread for you average every day radio tinker

By the way,
have a peek here at the shop
http://www.worldwidedx.com/station-mobile-pics/33726-my-setup-my-repair-bench-3.html

 

[KennyD]

I think I need to build myself one of those freq counter pre-amps if you have the schematic to share. I am not an electronics tech. I am an electrician by trade, I am just wanting to learn and work on my own equipment.

Ok thanks, I will check out c371 as soon as I get a chance. It looks like getting that board out of the box will be a lot of work if I need to change out caps and transistors, looks like all those filter coils need to be disconnected to get it out. Some of them ceramic insulated thru-pins look cracked too.

 

[Radio Tech]

I think I need to build myself one of those freq counter pre-amps if you have the schematic to share. I am not an electronics tech. I am an electrician by trade, I am just wanting to learn and work on my own equipment.

Same thing bro, just the electrons flow a bit differently

I will hunt the circuit down and post it. Works nice!
I am no master guru. Just an old country boy that learned the hard way. Started this when I was around 12. 53 now. Doing it all my life.

 

[Eastside]

That is one of the nice features of the CB-42. not only does it have 455 Kh but it 3.75 Kh to 12 MHz continuous tuning at 0-30-10%mod.

Looks like this forum is due for a shop talk / test equipment thread for you average every day radio tinker

By the way,
have a peek here at the shop
http://www.worldwidedx.com/station-mobile-pics/33726-my-setup-my-repair-bench-3.html

Again thanks....the CB-42 starting to sound better n better.

 

[Radio Tech]

Yeah I agree it sounds better, But, when it fails it dies a hard life. The main thing with the CB-42 is keeping the power rails in line. Speacially the 5 volt rail. It has to be spot on. Those TTL circuits do not like anything other than that. Most I have seen start off with the display going crazy and no longer reads. Followed by tuner failure. Had them on the bench and spent 40 plus hours scratching my head on them. I still have the first one I ever bought when a partner and I opened a CB shop many years ago. The only thing that works on it is the tone generator. One day I will restore it....

 

[Eastside]

Yeah I agree it sounds better, But, when it fails it dies a hard life. The main thing with the CB-42 is keeping the power rails in line. Speacially the 5 volt rail. It has to be spot on. Those TTL circuits do not like anything other than that. Most I have seen start off with the display going crazy and no longer reads. Followed by tuner failure. Had them on the bench and spent 40 plus hours scratching my head on them. I still have the first one I ever bought when a partner and I opened a CB shop many years ago. The only thing that works on it is the tone generator. One day I will restore it....

Thanks.....what kind of rf generator do you use on your bench?

 

[Radio Tech]

My main RF generator is the IFR 1200S with spectrum. This piece cost close to 10 grand new. Since I work on a lot of Ham radio I find this to be the best monitor I could get. Back when I worked for GE mobile radio service I used Wavetek and Cushman. When I left there and went to EF Johnson I had a IFR 500 and 2 IFR 1200S. That is when I fell in love with IFR.

But for basic CB work I use the 2040. Have one on all 3 benches.

 

[Eastside]

My main RF generator is the IFR 1200S with spectrum. This piece cost close to 10 grand new. Since I work on a lot of Ham radio I find this to be the best monitor I could get. Back when I worked for GE mobile radio service I used Wavetek and Cushman. When I left there and went to EF Johnson I had a IFR 500 and 2 IFR 1200S. That is when I fell in love with IFR.

But for basic CB work I use the 2040. Have one on all 3 benches.

Do you have any economic suggestions for a hobby old tube radio guy that just wants to do alignments?

I guess that answers my question.

 

[Radio Tech]

You talking for Cb or ham radio also?
For just Cb then a test radio is your number one piece of test equipment you can have. You can monitor a radio you are working on. Verify that the radio will produce a 27 meg signal although it may have no output. You can even use the transmitter in the test radio to tune a radio's receiver you are working on.

A good volt meter is a must. Not just one but several.

A scope is a nice thing to have. Minimum of 60 MHz. If a scope is not in your budget then a good VTVM with a homemade RF probe will get you there.

You also need a frequency counter. Not one of those RF through counters.

Dummy load. Home made is fine and cheap.

Power supply. Need several of them. A standard fixed 20 amp to run radios off of and a variable dual output low current supply. This is used for supplying missing voltage to a stage to see if will bring it back to life and for your projects.

Plus there are many thing you can build to help.
I am going to start a new thread tomorrow on this so we do not tie Kenny's thread up

 

[KennyD]

Is an RF probe necessary for testing anything in a radio circuit or just specific parts? I have 2 RF probes, one home made and one home made by a 3rd party and I'm not even sure if I am using/reading them right, they will give me different readings on the same test source. Should I not be testing the transistors and caps on my 2040 or any radio with a standard DMM?

I thought just using a VTVM or a DMM was all that was needed for most testing. I built the RF probe from a kit in an attempt to read the 5 millivolts required from the RF Out of the 2040 but with no success. I even have a Boonton/Motorola RF millivoltmeter but the probe I have for it does not belong to it. Without some sort of RF Millivolt Standard to calibrate my probes to I have no clue which one is giving me a correct reading.

 

[Radio Tech]

Is an RF probe necessary for testing anything in a radio circuit or just specific parts? I have 2 RF probes, one home made and one home made by a 3rd party and I'm not even sure if I am using/reading them right, they will give me different readings on the same test source. Should I not be testing the transistors and caps on my 2040 or any radio with a standard DMM?

I thought just using a VTVM or a DMM was all that was needed for most testing. I built the RF probe from a kit in an attempt to read the 5 millivolts required from the RF Out of the 2040 but with no success. I even have a Boonton/Motorola RF millivoltmeter but the probe I have for it does not belong to it. Without some sort of RF Millivolt Standard to calibrate my probes to I have no clue which one is giving me a correct reading.

You would use an RF probe mainly for just that, checking for RF in a stage that would produce RF. I do not use an RF probe for accuracy. I use my scope for that. The RF probe is good for making a quick check. Unless you used top quality parts and have everything laid out to a tee, your test may vary. I would not stress over it.

BTW on those voltages you posted. Check the positive side of 361. that is your 15 volt input to this circuit.