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139XLR update/more info needed

packrat

Active Member
Sep 24, 2008
749
19
28
S.W. Florida
OK, I have the radio working thanks to the help of the people on this forum, and here is an update.

AM power is about 6 -7 watts on channel 40 and 2-3 watts on channel 1. How do I balance it ?

SSB power is only 4-5 watts on my peak reading watt meter, and CT7 does nothing? Any help here?

CI54 and CI55 have both had one leg cut and lifted. Why?

Audio is reaching 100% with mic gain fully up and a power mic, also fully open. Only getting around 60 % with stock mic. Seems low to me, but adjustment VR 7 is wide open. I cant see VR6 anywhere to adjust it. Can someone point me to it? I have looked til I am cross eyed. LOL

Thanks again to all of the people who have given me help to this point.

PR
 

VR6 will have wires going to it and the other end of those wires will connect to your DYNAMIKE control on the front panel.

the reason they did this is because in a few models, there was no external mic gain.

i will look for the other info and post back later.

are you sure you dont mean C154 and C155?
LC
 
LC,

Thanks for the help. I was wondering if VR6 was actually the dynamic control. One mystery solved. Yes, , those are the I am refering to. C154 and C155. They are on either side of the ssb adjustment.

Thanks,

PR
 
im not sure why someone would cut either of those caps.

its possible that cutting C154 might have some effect on SSB power, but i wouldnt do it if it were my radio.
it parallels CT7 and is a 10pF cap.

C155 might have been cut by accident when someone was trying to cut C154.
thats the only reason i can think of that someone might cut that cap.
C155 is a 1pF cap.

you might look on the solder side of the PC board to see if there have been caps added where C154 and C155 used to be.

you should find that CT7 has an effect on your SSB power once you replace C155. (replace both though!)

as for balancing the power, first go to channel 40 and turn VR8 down until you are deadkeying about 4 watts. (best not to align the radio with the power turned up)

now go to channel 20 in AM mode and turn the DYNAMIKE all the way up.
(use your stock microphone)

you will need some wooden or plastic tools to turn the coils to align the TX.
using metal jewelers screwdrivers will affect the reading and they also tend to break the ferrite cores of the coils. (if you do happen to break one, unsolder the whole can, and unscrew the ferrite core from the bottom, turn it over and screw it back in)

ok, key the mic, and while saying "ahhh" into the mic in a normal voice; adjust L39, L37 (both cores) L32 and L30 in that order for maximum modulated wattage on your wattmeter.
dont try to adjust them for max deadkey, or you wont have any room left for modulation.

now go to channel 40 and deadkey the radio. note the wattage.
go to channel 1 and deadkey the radio. note the wattage.

if there is much difference between them, adjust one of the cores of L37 on channel 1 and the other one on channel 40 to balance the power out.
it really doesnt matter which core is which, but if you cant get it right with minimal adjustment of the cores, try it the other way.

it really shouldnt take much adjustment of L37 to get the power evened out, because you already "peaked" it on channel 20.


here are a couple of other things you should do to your radio.
look around the walls of the chassis for any transistors mounted to the walls that are labeled 2SC1419.
replace them with NTE152 or 2N6487 transistors.

the 1419 is weak and prone to failure.

there are 4 total. three on the main PC board and one on the power supply board. replace them all.
one will be on the same wall as the driver and final.
one will be on the back wall, and one (TR36) will either be mounted on the back wall also, or mounted to the short wall around the PLL section.
if its mounted to the PLL section wall, move it to the back wall next to the other one.

remove R153 (right behind old TR36 location) and solder one end to the center leg of the new transistor. solder a wire to the other end that goes to the old R153 hole (the hole that goes to a trace that runs along the edge of the PC board, not the hole that connects to where TR36 used to be.)

run wires from the other two legs of TR36 and solder the other ends to where those legs used to go.

its easier than i made it sound LOL. its late and maybe i didnt explain it very well.

the reason for this is because TR36 and R153 get quite hot during normal operation and because they were so close to those two crystals you see, they would cause the radio to drift on SSB.

there ya go!
you should have a nice radio after all this.
remember that this chassis is quite old and the electrolytic caps do tend to dry out over this many years.

i replace ALL the electrolytics in my 858 radios, but thats just me.
have fun,
LC
 

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