President Jackson export does not key

[Lkaskel]

Hi Everyone,
I have a President Jackson that has not been used an a few years as the owner had passed away. It was supposed to have been in working order. The radio is in perfect shape and base on the solder side of the board it appears to be untouched. The radio does receive fine and on freq. It does not key thought. By that, I mean that it does not go into transmit "mode". When you key the mic the receive stays active and the RX light stays lit. I have checked for broken wires on the mic section, tried numerous mics as well as my TX box on the bench and...nothing. Any thoughts?

Thanks as always!!!

 

[Dmans]

Lkaskel,
I just finished one of these for a good friend of mine. I replaced ALL of the electrolytic capacitors and repaired a couple dozen bad solder connections on the board (magnifying optical lenses are a necessity-for me anyway).
I also replaced the wimpy 20 or 22 ga wire from the circuit board to the center pin of the S0-239 (doubt that was the issue but felt cheap to me) with a piece of 16 ga tinned buss wire.
Several other issues with this radio were repaired but probably not related to the “not keying to transmit”. (Inoperative meter, frequency not following band switch etc)
First thing I did was remove and test the driver and final transistors- if the final was bad it would probably have totaled the radio/repair.
My suggestion is to replace all electrolytic capacitors first. I tested all the originals and may have found one cap that was within 20% of the original value. All others were BAD.



Good Luck

73
David

 

[undertaker]

Trust this gentleman he knows his stuff!!

 

[Dmans]

 

[Dmans]

Lkaskel,
I just thought about another possibility here. The Squelch knob also activates the PA function when turned fully counter clockwise. It is probably the same pot/switch combination as the volume control. If you "turn on" the squelch knob, PA function is off and TX is enabled. Ask me how I know.

Good Luck
73
David

 

[sp5it]

Replace every part in radio. At some point you'll replace that faulty one

 

[Lkaskel]

Lkaskel,
I just thought about another possibility here. The Squelch knob also activates the PA function when turned fully counter clockwise. It is probably the same pot/switch combination as the volume control. If you "turn on" the squelch knob, PA function is off and TX is enabled. Ask me how I know.

Good Luck
73
David

Thanks so much for your thoughts David!!! I do have one "logical" question. If the driver/final are bad wouldn't the radio still key/switch to transmit? The reason I ask is I have had a few folks mention that I should expect that they are bad and I have never noticed in other radios that in the case where they were bad that it kept the radio from keying. The fact that the radio stays in receive tells me that it would likely be something else.

Thanks again!!!

 

[Low_Boy]

The one I had that did not work had a few bad solder connections. Like Dmans said a good magnifier or a stiff tooth brushing while keying will usually work. When the TX light comes on you found your spot.

 

[sp5it]

Check TR32, TR33, D59, D61 if not defective.
Take a piece of wire and connect cathode of D61 to the ground. (Not chassis ground).
Come back with results.

 

[Dmans]

If the driver/final are bad wouldn't the radio still key/switch to transmit?

It may still transmit with a bad final. But try finding an MRF477 replacement. $$$$$$$

I think in my case it was the old, leaky and aged out electrolytics causing the problem. I did test every one of them when removed and was surprised at how low the values were.

73
David

 

[nomadradio]

Now and again the PA switch in a Galaxy Saturn will fail to close one circuit and the radio stops transmitting. Clicking it to "PA" and back a time or three magically fixes it.

For a while.

YMMV.

73

 

[Lkaskel]

Check TR32, TR33, D59, D61 if not defective.
Take a piece of wire and connect cathode of D61 to the ground. (Not chassis ground).
Come back with results.

Hi there, The parts all checked out and grounding D61 did not make it transmit.

Thx

 

[Dmans]

The parts all checked out

Assuming this means the CB/PA switch is good?

Have you tried to ground pin 7 of IC4 directly? Does R172 measure 27k ohms (out of circuit) or is it open? R173-10k ohms? Or open? How is the "health" of C133?

73
David

 

[undertaker]

Just send it to DMans..

 

[Dmans]

Probably should check the PLL lock detector pin as well.

73
David