[Uniden] APX191

[Glen Zook]

I am having problems with my APX191 adapter cable for the AMX-500C programming unit.  For some reason I am no longer able to program SMU300K units that I have been able to program in the past.  In fact, I have 2 of the AMX-500C units and both work fine when programming the removable PROM and E-PROM units.  However, neither one will now work with the APX191.

I replaced the diodes (1N914 types) in the APX191 and even tried Schottky diodes.  Also replaced the microphone style cable and still "no go".

The units all have serial numbers starting with a "9" which indicates that they can be programmed with the AMX-500C / APX191 combination.  Also, I have tried the programming set up with units that I have been able to program before.  

One thing that I am "thinking" is that there may be something in the SMU300K units that is preventing them from taking the programming.  These units have been "sitting" for several years without power being applied.  I do have the service manuals on the SMU300K, just need to find them!

There are several amateur radio operators in this area that would like to use the units and they make it down to the 440 MHz to 450 MHz segment without any problem.  However, I have tried frequencies in the "normal" 450 MHz to 470 MHz range to program and the units still will not take the program.

Anyone have any ideas?

Glen, K9STH

Website:  http://k9sth.com