Silver faced President Jackson

[ExitThirteen]

Stumbled across a silver faced President Jackson at an auction recently, was a disaster inside. TR 26, 37, and 41 were pulled, it had one of them silly "M80" thingys bridged across the 2SA473 (*sigh*) and had the biasing on the driver and final cranked all the way up.

I went through it all, replaced all the transistors, pulled the "M80" thingy, readjusted the biasing on the driver and final, and did a realignment.

I've had excellent reports on it since I got it fixed, but I noticed 2 things:

1) The AM doesn't swing worth diddly. I have it at a 5W deadkey and it swings about 7-8 watts. Any suggestions on how I could improve it a little bit without tearing it all up again? (Not a big deal if nothing can be done. It swings 45-50W on SSB on my Bird 43A thru-line meter, and I talk 80% of the time on SSB, just would be nice to get a lil more out on AM.)

2) When I'm talking to a close-up station on SSB, I think the AGC is causing the receive to chirp/garble a bit, if I turn back my RF gain, close stations on SSB clear right up. Any suggestions on how to fix this? I seen a mod on the Defpom site for this, changing values on R41, R43, and R47, and removing C31 out completely. Is it any good?

Of course, any suggestions and/or tips are much appreciated, thanks in advance!

 

[loosecannon]

the jacksons had a few issues that were discussed in the old secret cb books back in the day.
you can buy the whole set on cd-rom on ebay for about 10 bucks.
good reference material to have. (just watch for the typos!)
LC

 

[ExitThirteen]

Hmmm, the old CB secrets books, eh? I got a buddy that has that series of books, maybe I'll have to ask him about it, see if he's got info on this old Jackson I have.

I took this radio out to the mobile today. I run a 102" steel whip, 18 foot of RG-8 coax, and 6 gage wires to the battery for my amp and radio. I got 55 watts out on SSB on my Bird 43A meter, with about 1/2 watt reflected back in (about 1.1 SWR). I did the checking without the amplifier inline. I must say I'm super impressed with this radio on the SSB. FM is loud and clear also. The AM is a bit subpar, but at least on the Bird meter it does swing forward a little bit, indicating that it modulates decent, it's just not as much as I'd hoped for. I think I'll leave it alone as far as that goes.

Hopefully the CB secrets books may provide some info on how I can modify my AGC so close SSB stations don't wash out my receive. I really noticed it in my mobile when I get in someone's driveway, LOL...

Thanks for the info, LC. I'll check out those books.

 

[bob85]

yes do the agc mod, the mod is also in the uniden export manual, makes a big improvement with strong ssb stations.

 

[ExitThirteen]

Is the AGC mod I described in my first post the same one in the uniden manual? Or are they different mods? Just don't want any confusion here.

Thanks!

(edit) Forgot to mention, the board is #PB042, if that helps.

 

[bob85]

the resistors you listed are the same resistors,

remove C31 (.47uf )

change R43 (10K) to 1k

change R41 (150K) to 270K

change R47 (1.5K) to 3.9k

for some strange reason the maker got the agc timing wrong from the outset and never bothered to rectify the situation throughout the production life of the jacko,
the above mod from lou franklins book fixes it nicely, i have done plenty for locals over the years, without the mod they are useless for talking to very strong ssb stations locally or in good dx conditions,


good luck.

 

[ExitThirteen]

Most Excellent, Bob, thank you very much!


Thanks LC and Bob85 for the replies!

 

[ExitThirteen]

Update...


Performed the mod...simply incredible. No more adjusting the RF gain anymore on close SSB signals! My Jacko is rockin'. Thanks!

 

[davegrantsr]

they were NOT AM performers like the grant silver faced export of the same era. i have posted SOMEWHERE on this forum a quote explaining the reasons why......may be in a thread regarding the new jackson II radio......

 

[ExitThirteen]

Yeah, I read that also that the Jacksons were not big AM talkers. I'm really not worried about that, the AGC mod is done, and I backed off the SSB ALC a bit, brought it back to about an even 50W. I get so many compliments on how good it sounds. It talks good AM, just don't have that superswing that the Galaxys have, which is fine. I'm a happy camper. Cheers!

 

[15minigrass]

Im getting 2 Jacksons. Gonna see if it has been modded for this.

 

[jazzsinger]

Yeah, I read that also that the Jacksons were not big AM talkers. I'm really not worried about that, the AGC mod is done, and I backed off the SSB ALC a bit, brought it back to about an even 50W. I get so many compliments on how good it sounds. It talks good AM, just don't have that superswing that the Galaxys have, which is fine. I'm a happy camper. Cheers!

i'd be backing off that alc a bit more substantially,the radio is only designed to do 20w pep on SSB and 10w on AM/FM.the mrf 477 output for it is discontinued or costs a fortune if you can find them,you certainly don't want to be popping it running 50w pep.

the AM on it was never great,it uses low level AM modulation unlike the grant export which uses high level AM and has much more punch on AM.It's the radio's ability on SSB that made it huge here in Europe,and the fact it has decent FM performance too which is more prevalent here than AM.

Not sure what you have AM carrier level set for but 10w is maximum it will do before audio suffers.

The silver jackson is probably one of the best SSB radios uniden ever built.On SSB its on a different plane to Galaxys.

 

[kc8adu]

+1 on cut the alc a bit.
and if you do kill the mrf477 there is a mitsubishi sub with the same bec basing.had one in mine but cannot remember the number.the 477 can do 40w pep but the failure rate was high probably due to high swr.freq range is wide enough that it is easy to forget your antenna is no good at the extremes these things covered.ran mine mobile 10+ years.and mine was also a wreck when i got it.funny thing was the agc mod was done already and was done professionally.
spent a lot of time cleaning up all the solder shorts,mangled traces,scredriver drift and found the only bad part was the so42p mixer.

 

[ExitThirteen]

Wow. This post got dug up from the archives? That's kinda funny.


I sold this radio to a friend of mine a while back, he loves it. Still has the original MRF477 in it, still does 50W on my Bird 43A into a dummy load. He shoots skip a lot with it. The AGC mod I did on it was amazing though. Thanks to all who helped me with that mod. Cheers!


-Exit

 

[15minigrass]

Is there any way to pump up the AM side of this radio? i.e. low deadkey swing max????