Kenwood TS520

[datsun66]

I fired up the radio and when I was tuning the radio I herd a pop and the transmit went to 0. The rf I could get is when I loaded it up on 80 meters and that was only about 10 watts.
I checked the 6146b tubes and they check out fine and so does the driver tube. The radio will adjust on the bias to 60 ma but that is it. I liked around for any blown caps or diodes and everything looks good. No shorted air cap wafers either. I even checked all of the diodes in the radio and they look good. I could not even see any thing blown. Yes this radio did come from a smokers house so I had to clean it up somewhat but that was 5 years ago. Receive works.
Any Ideas?
:mad
MERRY CHRISTMAS EVERYONE

 

[Captain Kilowatt]

Check for plate voltage but be carefull it is around 800 volts.It could be in the power supply section,maybe a diode has opened up. Also check for filament voltage on the driver and finals.You may have even blown a series coupling capacitor between the driver and finals.Nice rig when they work. I have a newer 820S and love it. Good luck.

 

[datsun66]

I forgot to mention, The tubes light and when you load them on 80 meters, the two finals do heat up. I do have high voltage.

 

[Captain Kilowatt]

I would check for open capacitors in the driver/PA stage. A series ceramic cap may have opened and would be impossible to tell with just an ohmeter.A bypass cap could have shorted to ground as well. Do you have a schematic to follow? I have one I can email you if not. It is 2Mb in size as well as a user manual that is 3.75 Mb and has diagrams as well.Both are PDF format.

 

[datsun66]

I have all of the schematics, the cap checker I have, may be able to check them. I use it to work on antique radios but mostly electrolytics.Its a heathkit. What is the best way to check the ceramic caps?

 

[Captain Kilowatt]

Do a simple continuity check to check for shorts first. Then lift one leg and connect it to your cap checker.See if it measures anywhere near the marked value.Sometimes a .01uF may measure only a few pF.Check C3 located between the driver plate and the finals grid.See if you have drive available at the input to the finals.Pull one final at a time and see if there is any differance. If you can replace the driver first and then the finals to make sure. I know you said the tubes are fine but often the driver or final will blow when tuning. Other than that I will have to wait until the eggnog wears off to come up with any more ideas. Hope you're not in a big hurry.

 

[datsun66]

No hurry, It's just my luck, Get a new beam antenna and the radio dies.