Tech Help President Jackson

[CTStallion]

Folks,

A friend of mine gave me his President Jackson to look at because of no RX or TX. The Jackson is a 5 band AM/FM/SSB transceiver.

This radio has special meaning to him, as was his late Father's.

Anyway, radio lights up and works good on PA mode, but no TX or RX. Last time the radio had trouble (1997?) it was for cold joints in the VCO area. Checked for same and 'resoldered' everything in the area.... nothing.

I also replaced the oscillator crystal..... nothing.

Should've checked the caps and/or transmit/rx transistor (if so equipped), as the RX light works on RX, but the TX light does NOT come on when I key the mic in any mode.

The service manual on CB tricks is pretty 'light' for this radio... dunno WHERE to start.

Any suggestions before I start swapping components to find the fault? (I'd really like to help him out w/this.)

Thanks

 

[TonyV225]

Did you try a different microphone before going through all that soldering work??

 

[CTStallion]

Did you try a different microphone before going through all that soldering work??

Yes sir, sure did.

In fact, the PA function works fine as well on all mics tested.

 

[mackmobile43]

You might check the center stand connection between the so'239 and the board for a cold joint.

 

[CTStallion]

Bump
for visibility

 

[kb6led]

check to make sure you have voltage to the PLL

 

[TonyV225]

check all the solder connections on the pins to the PLL chip on the foil or flatside of the board. Use something non metalic (non metal) something plastic or I use wooden doll stick and push around gentley to flex the board looking for bad trace if this is the case which in most cases it is as you push that certain spot you will here sound come in and out.

this will give you a general starting point of tracking down bad or cracked traces or solder joints usually to a ground.

 

[CTStallion]

check to make sure you have voltage to the PLL

I think THIS may be the problem, as I 'think' the VCO is looking to see approximately 6-8 volts, (changes as you change bands / channels), but I'm only seeing about 5 with NO change when I change bands.

Will a 2SA1012 replace a 2SA473? (cuz all I have in stock are 1012's)

From what I gather, the VCO won't work unless it sees at 'least' 6 volts or so, and (as you mentioned) the PLL has to LOCK at a certain voltage. I believe the output of the 2SA473 in this rig is supposed to be approx. 8 VDC.

Update: Changed the TR501 2SA473 with a known good NTE153, and replaced the 2SC945 TR34 with a new one. No change. Still developing only 5VDC to the VCO; PLL still won't lock. Going to local supplier to get subs for TR31 and TR33 to see if I can then develop voltage.

Getting the full 13.8V to the TP band to the final. Unfortunately the final is an MRF477, so still keeping my fingers crossed for the guy.

 

[kb6led]

I recently repaired a couple cobra 2000’s both had no RX or TX. The 1st one ended up being a shorted cap on the supply voltage side of the PLL. The other ended up being a bad 11.3258 mhz crystal (this one was an intermittent problem) my scientific method for discovering this was using a hair dryer and a can of cold spray, heating it cause the radio to stop working and cooling it back down it would work again.. Good Luck

 

[psycho]

If the radio didn't have sentimental value, it should be thrown in the dumpster because they are just low audio dogs when in working condition.
If money has to be thrown at the radio, advise him NOT to. I have never heard a Jackson sound anything but unimpressive.