Motorola SSB base CM555 channel mod issue in question

[Retro CB Guy]

Hi

I just took my in superb shape Motorola ssb base 555 to my local tech who has been doing this for like 35 years at least and there is a reason for this issue for which he couldn't nail down and fix exactly so I'm asking for input that could lead to a sure fix for this issue good folks !!!!!!!!!!!!!

As stated in the CB Tricks secret CB book that my upper channel expasion should be up to channel 59. My radio will only lock in to do up to channel 50. My tech adjusted the appropiate pots inside which he had to cut away some of the metel of the metal casing where those pots was to check voltage and adjust thing as well.

One thing though which was odd I should mention is the radio as has lower channels below 1 which aren't mentioned in the Secret CB book... So I'm thinking there is a posibility that that might be affecting my uppers ?
Also those lowers span alot of channels and are on half channels ending in zeros on the frequencys. The uppers check on frequency though as they should on the ones I have which is 42-50 !

So I know alot of veteran CB folks come on this forum and could likely help me out with the situation I have here !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

So here's to hoping and PLEASE respond if you feel you have something useful and helpful to my somewhat silly issue here so that I can get the missing 10 upper channels or so.

Thanks in advance and take care, RETRO (Jimbo)

 

[sonoma]

as old as the radio is you may have some electrolytic caps going bad on you causing the problem. all my old radios I change them out the 1st thing to make sure there is not any weak ones in it. may or may not be the problem.

 

[Retro CB Guy]

as old as the radio is you may have some electrolytic caps going bad on you causing the problem. all my old radios I change them out the 1st thing to make sure there is not any weak ones in it. may or may not be the problem.

Yeah could be the issue but that is much labor induced and still may not solve it (however it could) so I am taking all INPUT now for a while and go from there... This radio is in fine shape though...

Thanks for your input and time sonoma, Retro 73's

 

[Retro CB Guy]

Also like I said, this one gets tons of lower frequencys as in maybe 40 so I'm wondering how that plays into this ????????????

 

[Retro CB Guy]

I have an important update here folks please... Since recently I've aquired a couple more of these very nice Motorola model 555 ssb base radios...

Now I plan to get them all aligned up and reapaired as needed but I want one to do more upper channels and not these goofy channels below channel 1.

I'm gonna explain the EXACT situation that I have ! WIth the one that has extra channels, I will describe that...

Lower channels span from 26.5100 to 26.9500 and yes half channels ! My uppers are channel 42 to 50 and it runs from channel 12 on the channel selector onto channel 19 which is 50... Also channel 20-27 on the channel selector don't do anything or repeat channels sometimes...

So what is my issue here, how can I correct it ? Is there a proven method for obtaining just uppers or to have upper to channel 59 and correct the lower to be not half channels ? But I need details how to let my tech know please !

You guys pulled me through on my Robyn 540D so hopefully this radio too because now owning 3 of them, I would love to get these all going .

73's and hopeful, Retro

 

[ExitThirteen]

The CB Secrets book says to isolate pins 8 and 9.... one of those being the T/R pin. That's why you're getting 26.510 - 26.950. Pin 8 is the phase detector output pin. I suspect that method that is mentioned is wrong in some form. I don't see a reason to isolate the phase detector pin, or isolate the T/R pin.

I can't seem to find a lot of information about the PLL used in that radio (it's a TC9105P) so it may possibly be a Motorola exclusive PLL.

I don't know if it has internal pull-down resistors built into the chip, so if your tech is attempting to change the programming, and he's isolating any programming pins (cutting traces), he may have to solder in a 4.7k ohm resistor across the cut trace so the pin isn't left "floating". Then he can change the programming of that particular pin.

Do you have a schematic of the radio?

~Cheers~

 

[Retro CB Guy]

The CB Secrets book says to isolate pins 8 and 9.... one of those being the T/R pin. That's why you're getting 26.510 - 26.950. Pin 8 is the phase detector output pin. I suspect that method that is mentioned is wrong in some form. I don't see a reason to isolate the phase detector pin, or isolate the T/R pin.

I can't seem to find a lot of information about the PLL used in that radio (it's a TC9105P) so it may possibly be a Motorola exclusive PLL.

I don't know if it has internal pull-down resistors built into the chip, so if your tech is attempting to change the programming, and he's isolating any programming pins (cutting traces), he may have to solder in a 4.7k ohm resistor across the cut trace so the pin isn't left "floating". Then he can change the programming of that particular pin.

Do you have a schematic of the radio?

~Cheers~

YES I have the schematics brother ! I'll have to try to take a photo of it or scan it and get it to you. I'll contact you via through inviting to conversation so that I can get your email if that's okay bro ? I want to get to the bottom of this it's paramount I do now owning 3 of these... Thanks for this additional info though and my tech is on his game so this may be enough to head him to fix it I don't know.

Look for a conversation invite bro, Retro