Uniden PC-122 help

[KennyD]

Uniden PC-122 help. I picked up two PC-122's, one is an XL. Both radios had frequency expanders & unlocked clarifiers installed in them. Neither radio would align worth a damn onto the center notch so I want to return them back to stock. I removed the channel expanders but they still won't align. L38, L13, L14 are all set on the scope. But when you go to set the AM RX @ L15 the tank bottoms out before it reaches freq.

Any ideas?

 

[sdmahr]

What type of expander was in there you removed? Could be some components that were stock were removed in order for the expander to work....which are not there now causing your problem.

 

[KennyD]

What type of expander was in there you removed? Could be some components that were stock were removed in order for the expander to work....which are not there now causing your problem.

One was an Expo 100 N board with two crystals and the other I'm not sure the brand but it used two IC's instead. The 122-xl had the expo board and that's the one giving me the most trouble. I repaired the traces on both radios at the clarifier, and replaced the D25 diode that gets removed or clipped when these boards are installed. I added a resistor to the clarifier on the pc-122 to help recenter the notch and that radio seems to have aligned alright. But it's just a band-aid.

 

[sdmahr]

One was an Expo 100 N board with two crystals and the other I'm not sure the brand but it used two IC's instead. The 122-xl had the expo board and that's the one giving me the most trouble. I repaired the traces on both radios at the clarifier, and replaced the D25 diode that gets removed or clipped when these boards are installed. I added a resistor to the clarifier on the pc-122 to help recenter the notch and that radio seems to have aligned alright. But it's just a band-aid.

I don't have any experience with the Expo Board with the crystals....so cannot help you on that one. The other with the two IC's is a Galaxy N-Board, or a copy of a Galaxy N-Board. I would see if I could find installation instructions on how the Expo 100 Board is installed. It should tell you what has to be done to a stock radio to install it and it work properly. Reverse what was done and you should be close to where you need to be.

 

[Tallman]

But when you go to set the AM RX @ L15 the tank bottoms out before it reaches freq.

Any ideas?

L15 might be peaking on a harmonic. Back the slug almost all the way out (To the top of the can) and then slowly turn it in watching for a peak that might start as soon as the slug gets even with the top of the can. Catch the first peak and you should be good.
I worked at a Motorola factory and they had problems with false peaks in the radios.

 

[sonoma]

http://www.cbtricks.com/handyandy/PC-122/Reference.htm

here is a link to a lot of info for the radio you are working on, if you click on the links at the top of the page it has more info. the guy that wrote this up knows the radio better than most. the info has helped me with my pc122 and trc-453 radios in the past. these radios are bad about bad solder joints. you have to clean the old solder and flux from the suspect joints and resolder them. a few months ago I recapped my pc122 and realigned it and it works better than new. the caps could be getting old and drying out causing you a problem. I am talking about the electrolytic caps only.

 

[TonyV225]

I can tell you fro experience that for some reason those Clarifiers are goofy. I love those PC122 and sold one this passed year that I had installed the Expo Expander N kit in and that clarifier was touchy to where you had to turn it ever so slightly as it would take a second for the radios frequency to catch up to the adjustments I made!!1 I took the kit out when I sold the radio and put it back in its box. I those PC122 are OUTSTANDING SSB Rigs and I have a Uniden 640E which uses the same board and the radios are getting scarce but Im not sure Im even going to mess with that expo kit as its pointless. I just left the clarifier alone and just aligned the transmit frequency and it works great!! Ide do the same with the PC122 if I ever got another one. Im not sure why the clarifiers are so goofy in those Uniden PC122 or those particular boards.