The AM Forum

Ok , Time to restore the Johnson Ranger transmitter. After testing the transformers,  tubes and replacing caps and doing resistance checks what else should i look for? I have done several dozen receiver restorations but never a transmitter.

After all of that, and doing a visual inspection (looking at all the switches for any arcing damage), and finding any modifications (and doing the detective work to find out why and whether you should keep them in at all) should be it.

Once you've done all this, set the transmitter up for its lowest band, no drive, and bring her up slowly on the variac and listen for snap crackle and pop. If all is OK start checking B+, low HV, bias and filament - depending on how they list it in the manual, your measurement may be a little on the high side because of the low load. Then start carefully through the tune-up procedure (CW on the first pass, AM on the second), and look for wierdness; if you see anything, stop and figure out what is wrong rather then pressing on. If your manual has an 'expected voltages' table, setup your transmitter for the conditions indicated, and begin measuring. If you've a good handle on circuit theory, then go directly where the issue might be occuring.

Also, check if your VFO is working by using a digital portable reciever and checking operation on all bands (your manual will tell you what the VFO frequency is for each band).

Make sure the dummy load is appropiate for the transmitter, and that you've the right mic and connector.

Good luck.

If it hasn't been changed already, replace R-3 (the 18K dropping resistor to the VFO VR tube) with a higher wattage unit; 10 watt would be a good choice.  The resistor can be checked/replaced through the left side (your left looking from the front) of the VFO case without taking the entire case apart.  Some advocate moving R-3 outside of the VFO compartment but my experience is that the VFO stabilizes much more quickly if it is left inside.

If the VFO tuning feels rough then it is probably due to the grease drying out in the ball reduction drive.  You can remove this unit, clean it, and repack it with grease and you will end up with much smoother tuning.  The only "trick" is setting the tension on the balls properly when you reassemble it-too tight and the tuning will be too stiff and set too loose will result in slippage.  It really isn't that critical and the tuning will work pretty well over a fairly wide adjustment latitude.

As for mods, there are probably more out there for the Ranger than any other transmitter so take a little time reading up on them (the AM window is a good starting point) and decide which ones fit your needs.  My Ranger has the basic PTT mod and is used as a driver for my Desk KW.

If you do replace the rectifier tubes with SS then you will need dropping resistors in the Ranger to keep the voltage at a reasonable level.  There is a lot going on in a little space so the Ranger does tend to operate on the warm side.

Good luck with your restoration.

Rodger WQ9E

This link may be of help for restoring the Johnson.........


http://www.enzite.net/


klc

I hate the way they copied from smiling bob of the church of the subgenius. he dont need no stinkin pill.  >:(
(http://www.subgenius.com/Graffix/dobbs.jpg)

Kb2WIG- That really made me laugh, thanks.

whatta woodly remark ...beefus