RCI 2950 frequency drifts up away from 11m into 10m

[mr_fx]

I am messing with a RCI 2950 and it does the ODDEST thing. the frequency is stable a little below the 11m cb band and stable a little above 28mhz, I think it's about 28.4mhz actually.

Any way the TX and RX of the radio drift upward until they get into the 10 meter band

at first I thought it was an issue with the counter so I locked it in TX and listened from another radio. and sure enough the RCI would drift right past the frequency that the other radio was listening to

The 2 10.240mhz crystals are on frequency, one of them reads 10.23999, the other reads 10.22599. so they are in spec.

I found that when reading the L65 and adjusting VC2 that the frequency will align just fine to 17.30500Mhz, but after a minute or 2 the frequency will start rolling upward into the 18MHz range

 

[mr_fx]

so if the crystal is maintaining it's frequency then it's something near the crystal causing the issue, right?

 

[mr_fx]

well it looks like the only place that the freq stays put is in the lower bands, BUT in 10m the radio counts DOWN (instead of up) but not nearly as fast

 

[mr_fx]

I am really thinking that the PLL is not locking and basically it's just kinda rolling, maybe it's making lock in the lower freqs

 

[mr_fx]

turned the clarifier and the freq stabilized. might just be a bad clairfier pot

 

[mr_fx]

turned the clarifier and the freq stabilized. might just be a bad clairfier pot

also the clarifier seems to have about 1.5mhz of slide

 

[Robb]

Did you clean the clarifier pot?
Did you check the voltage that supplies the 10.240 crystal?
Is that voltage steady?

 

[mr_fx]

Did you clean the clarifier pot?
Did you check the voltage that supplies the 10.240 crystal?
Is that voltage steady?

I was getting ready too, however I dropped a plugged in soldering iron and when I got up to find i, I stepped up it... nice hot iron directly to the foot, lol man that burns

the one time I choose to not wear shoes while I am working on a radio, funny stuff for sure. good hing my feet are so rough or it would have been a lot worse

 

[mr_fx]

sometimes the radio will be on say 27.305, then you check the freq and it's on 27.7 something, then you turn the clarifier and it will be way off center, that and when this happens it will have a range of 26 mhz on up through 29 mhz, all by turning the knob, then other times it works correctly

 

[mr_fx]

well I tested the clarifier pot and it seems to be perfect. So that's not the problem

 

[ExitThirteen]

Your VCO is unlocking, and the most common problem that causes it is a bad solder joint. It's a pain in the butt, but touch up all the solder joints in the VCO section of the radio. I bet I've worked on several HUNDRED of these older 2950's that had problems with VCO issues such as this. Double check your work when you're done. Good luck!


~Cheers~