Realistic TRC-449 clearifier relock. Problem.

[Low_Boy]

So years ago someone did the secret Cb clarifier unlock to this radio. They added a few extra channels that I removed. the radio was working but I could not center the clarifier so decided to remove that mod also.
So what I did.
Solder pin 19 of the PLL back to ground. (This must be part of the extras.)

R62 back to a 4.7K they had replaced it with a 1K

Reinstall D30 and D32 they were lifted whoever did the mod lifted R117 instead of R119 so R117 back.

Vilot wire put back and brown wire put back where they belong.

PROBLEM: now everything is 10K off. CT 4,5, and 6 only tune to 33.xxx and will not tune to 34.xxx and that must equate to the 10K off. what am I missing?

 

[Handy Andy]

Did you unsolder Pin 19 and re-try?

 

[sonoma]

check what Handy Andy mentioned. you may have a 11.3258 crystal in it also. did not see where you mentioned that. if it is a 11.3258 pin 19 needs to be left unsoldered.
I ran into that on a radio I did a few years ago.

 

[Low_Boy]

Working???? All can think is I pulled the crystals to verify they were correct. and one must have not been making contact. On frequency now after another adjustment. Pin 19 still grounded.
x6- 11.2850
x4- 11.2842
x3- 11.2858
x1- 7.8025
x2- 7.7975
No clue Thanks

 

[Handy Andy]

SIDE NOTE:

This Xtal-swapping has been a chronic problem in Radios that can take these frequencies.

More than once I've been confronted by those "Monsters"

When you cant make the Higher Frequencies, that may indicate C140 and C141 SEE GRAPHIC - ORIGINALLY were Tantalums, may have drifted off in tolerance and so they lose their High-Frequency tolerance. It's part of the PLL phase-lock "Gating" section - High-Speed versus Low-Speed and "Window in-between" per the divider pins that includes Pin 19.

​

Did you mention that you have the Clarifier "re-locked?"

Ok, then check your TX trimmer too. SEE GRAPHIC BELOW

​

Because, if you did reconnect and separate the RX and TX to track together - then you have A COMBINED voltage from RX and TX summing together instead of being separate - so you may have to look for a crossed over jumper somewhere that would bee the Feed line for your RX and your TX but not both - together.

Now, you also should re-check the voltages on your Clarifier - a 2 volt difference can make it appear like a similar problem that Grant and Cobra 148's had, that bumped up 10kHz offset because you are sending more voltage that the Varactor needs. That was caused by the owner wanting more slide - got "in-between channel" mod on top of it and when you un-do this - you have to make sure your resistors are correctly valued and in the right holes else you find your 10kHz slide and you're on the A's not on the B's of the CB-side of things...

 

[Handy Andy]

Working???? All can think is I pulled the crystals to verify they were correct. and one must have not been making contact. On frequency now after another adjustment. Pin 19 still grounded.

Ok, I just posted the above AFTER you said you got it working - Do you want it to stay up? Else I'll remove it...

 

[Low_Boy]

You can keep it up or remove it if you want.I also noticed when I unsoldered it they had the pad pulled up. So I am wondering if pin 19 was touching ground but pin 21 and 22 were not touching pin 19 so I bridged it a bit better. Thanks Andy,

 

[Handy Andy]

Thanks - I didn't want it to reflect upon you, it would just otherwise had to be archived and re-posted and may not even be able to apply. (I probably would have forgotten it - not unlike the old days where I had a thread or two just to put stuff out there as cheat / Cliff notes...)

The graphic is from a compilation of other notes - including a Service Bulletin from Cobra. That dealt with issues of unable to stay locked, or clarifier not centered.

I feel that it may help others in the future - so thank you - at least it stays with the radios' schematic - being it is specific to the radio, but the problems that occur, can happen to many other chassis' not just with the 858 PLL.

Glad to know you got it working!
:+> Andy <+:

 

[Low_Boy]

But I hate when I can only guess what I did. LOL

 

[Low_Boy]

Well. Was working the other night. I just tried it before putting it together back to 10k off freq. And now 1/10 of a watt output power. I will check the Tantalums you mentioned. The no output power is a stumper.
6.1v RX. No volts TX.

 

[Low_Boy]

Definitely a PLl problem.
1 thru 7 work perfect.
8 and 10 nothing
11 thru 40 10 KC off.
Still poking around
Vco voltage good..

 

[Handy Andy]

May be a bad array...see above - look for RR1 - they are Resistor Arrays, a bunch of resistors with one of their ends tied to a common and the others are free to acts as the designed needs, pull up (the common end to V1) or down the common end to Ground.

Might be a good idea to make sure the BCD is following the Truth table. If one or more of the resistors (if they are even used on the board) in those arrays gets flaky, it can make the line appear open or dead short - holding it in a state that can make your radio appear to jump channels.

Same goes for the CC array, same thing - only uses Caps to filter out noises. They're always open, but if any physical damages or static pokes ever hit the chip - caps can lose insulation in their plates' substrates (the suff that they're separated by) and show shorts

The PLL's back then used a different design of manufacturing and their substrates - back then how they make all those layers sandwich together and work - they had to provide different measures to protect IC inputs from ESD or EMP damages. They are not immune to static pokes nor do they take very kindly to them.

 

[Low_Boy]

Maybe there are many bad caps. C179 a 2.2uf Tantalum near the driver smoked while I was testing the radio. Tomorrow I will get PLL voltages. Probably should recap the radio.

 

[Handy Andy]

Oh wow!

Yeah, that would be a good start.

Sorry, thought since it was working, you had already done it...

 

[Low_Boy]

seems like it worked after clarifier mod was removed. Then it sat a day and stopped working. then worked and stopped. It has been a on and off experience. LOL.