johnson viking 1

[Number15]

Hope this is in the right section, here is the problem the radio has low modulation the guy i got it from thinks its a tube problem? but i dont know which tube? any info will help. was doing 100% now only around 50% percent modulation. Thanks.

 

[scout943]

You will have to find someone with a tube tester or a schematic or service manual . Try CB TRICKS .com . E F JOHNSON made some real good stuff !!! I am still using the radios I bought back in the 70s and they are still working fine!!

 

[W5LZ]

How do you know that it's about 50% modulation instead of it's normal 100%?
- 'Doc


The smartest thing you could possibly do is find a manual for that thing. Seriously doubt if you find an original, but a copy would do just as well.

 

[Beetle]

You can download a copy of the original manual from the BAMA website.

 

[Number15]

How do i know cause i put it on a meter, and other radio operators said that the modulation was weak. Also the original owner told me also. Thanks for the info guys. ((Also i found that the watts is low only 40?))

 

[W5LZ]

Being aware of how things 'were done' some 50 years ago, I would really suggest getting a copy of that manual. Along with a couple of spare 4D32's and 807's. It's amazing what that meter on the front of that thing will tell you, and very accurately too if it hasn't been 'diddled' much. It does have some faults which Johnson corrected in the version II model.
Some of the best advice you can get is to think very conservative with it.
- 'Doc

 

[Number15]

Thank u DOC

 

[HiDef]

The manual should be on B.A.M.A.

Additionally

You gots to run the final with at least a certain amount of grid current or the modulation will not happen correctly. Too much grid current and the final will die.

Many seasoned tube enthusiasts will tell you the best tube tester is the circuit said tube runs in. This is especially true for larger tOObs.

google amfone

 

[unit_399]

What kind of microphone are you running??? Early Johnson radios used High impedance mikes, so if you're using a 600 ohm mike, it will give you very low modulation.

- 399