PC-122 Troubleshooting

[Handy Andy]

As a sidebar...

The wax "creep" you will have, in this VCO mess - will be prevalent in your work - keep some good quality Isopropyl Alcohol or even some White Gas (care with it though) to help remove it to clean and dry the pads so solder will re-adhere the part to the foil.

In my situations the caps, C63 and C64 - don't or at least don't sit in the mess - just by it, so it's easy enough to remove. However, you may have to take an effort or two to get the new caps to settle in to their new spot.

 

[WECSOG]

As a sidebar...

The wax "creep" you will have, in this VCO mess - will be prevalent in your work - keep some good quality Isopropyl Alcohol or even some White Gas (care with it though) to help remove it to clean and dry the pads so solder will re-adhere the part to the foil.

In my situations the caps, C63 and C64 - don't or at least don't sit in the mess - just by it, so it's easy enough to remove. However, you may have to take an effort or two to get the new caps to settle in to their new spot.

You're right; the wax doesn't interfere with C63 and C64 to any great degree. I do plan to do a bit of cleanup, though. There is quite a bit of rosin flux that wasn't cleaned up when it was built. I have 91 IPA, maybe some 99 IPA, denatured alcohol (ethanol), and acetone. I was thinking about using the acetone and a brush.
Back when I was in the electronics business, we used to dunk boards in boiling perchlorethane tanks. Now that got them clean!

 

[sonoma]

I have several of this version radios and any of them that set for a year or longer do not want to work when I hook them up. every time I find some solder joints that have gone bad. after going over the solder joints in the PLL, VCO and crystal areas the radios come back to life. I have trc-453's.trc-465, and uniden 122 radios and all have done this to me after setting for a long time. as long as I use one daily it fires up every time. just let it set for a year or so and have to check for solder joints. I have never been able to get one to stay fixed after setting for a long time.
Handy Andy is the guru for these type radios maybe he can bring some light on this matter.

 

[WECSOG]

I have several of this version radios and any of them that set for a year or longer do not want to work when I hook them up. every time I find some solder joints that have gone bad. after going over the solder joints in the PLL, VCO and crystal areas the radios come back to life. I have trc-453's.trc-465, and uniden 122 radios and all have done this to me after setting for a long time. as long as I use one daily it fires up every time. just let it set for a year or so and have to check for solder joints. I have never been able to get one to stay fixed after setting for a long time.
Handy Andy is the guru for these type radios maybe he can bring some light on this matter.

Thanks! That's good to know, on the solder joints.
You're right about Handy Andy. I really appreciate him showing up in this thread to help me out. And everyone else, too.

 

[Handy Andy]

I'm adding this as a means for you folks to review and proceed as needed...

If you get stuck - review all these notes (not just this page but all posts from me in this thread as a guideline), and realize that although some Graphics talk about Clarifier or VCO but not exactly pertains as we have here, - these graphics are from another time helping others and due to the level of details involved in the parts layouts as well as the descriptions of the various areas, the information still can apply in some indirect fashion to what we have going on in this thread.

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I'm adding another new one to this for voltages, which seems to be quite important for getting the older versions to start working again.

As you know the Channel SELECTOR uses a Detent to help the PLL determine if the Pins are programmed properly and that the Power to the chip has not failed. The "Detent" is a Normally open - but as you ROTATE the switch closes and voltage "drops" off of Pin 15 which is reflected on Pin16 output (Pin 15 it's simply a buffer amp) so the LOADING on one pin - in this radio - Pin 15 - doesn't load down Pin 16 - it uses the PLL's 5V power but NEEDS to make sure Pin 16 is Good - Detent and PLL Power Zener regulator on Pins 7, 11 are LOOKED at and also Pull up and buffer resistors R107 (10K) and R108 (12K) are applying power to the pins 15 and 16 - once things are good, the VCO then decides if the Channel Selector Pin programming is good and follows thru.

Pin 22 looks at L38 as Fin from Low pass filter (C59 L12 and C61) as Phase Detect Input to Programmable Divider, Pins 18 and 19 are a free running loop oscillator that Pin 22 uses for "Gating" and Error Correction is on Pin 17 into that Loop Oscillator while pins 12 and 13 are clocking input of the ~ 10.240MHz and Pin 10 is 1/2 out of what 12 and 13 are. When VCO loop can't be detected or tracked - Pin 17 goes low - stays low to stop Pins 18 and 19 from working. Pin 10's output is applied to L38 as a means to obtain and keep the Local Oscillator running in most conditions and also to "reset attempt" to start Lock process over again. (This description is subject to revision)

Other aspect was the Quality of the Capacitors used, C63 and C64 need to be computer grade level 2.2uF 50V types, while another Power Smoothing one, C65 is a 220uF 10V type, and the Pin 16 Smoothing Lock jitters Cap is C63 of 1uF 50V.

Again, these "Ratings" varied as the parts lists will show, but if you can obtain Type "M" 20% tolerance you should be ok and good to go.

 

[Handy Andy]

I have several of this version radios and any of them that set for a year or longer do not want to work when I hook them up. every time I find some solder joints that have gone bad. after going over the solder joints in the PLL, VCO and crystal areas the radios come back to life. I have trc-453's.trc-465, and uniden 122 radios and all have done this to me after setting for a long time. as long as I use one daily it fires up every time. just let it set for a year or so and have to check for solder joints. I have never been able to get one to stay fixed after setting for a long time.
Handy Andy is the guru for these type radios maybe he can bring some light on this matter.

Another note to help you Sonoma...

The Zener used at D36 you can probe and make sure it's able to "hold" the voltage up high enough for the PLL to function. When the VCO is running and you have a "lock" probe that Pin 7 or 11 for voltage and make sure it's higher than 4.8 volts. IF not...read on...

You can increase the Zener to a 5.6V 1-watt type if you encounter problems with dirty switch detent in the channel selector or that the Resistor Butter array in and around the Power Good and the Lock Pins 15 and 16 are drifting off - the extra voltage helps offset a sensing issue and I've found it works well. BUT you do have to remember that the channel display also uses this power in one fashion or another - be aware of losing Channel display segments if and when you need to increase the 5.1 Zener to 5.6 to overcome voltage dropout issues elsewhere...

 

[WECSOG]

Ok, I replaced C63, C64, and C83. C64 was reverse polarized according to the schematic, and the silkscreen on the board is incorrect. I put the new one in per the schematic, which shows negative to pin 18 of IC2.

No dice. Still 7.35 VDC on TP2.

 

[Handy Andy]

Tweaking L38 too?

Any Signal on TP4? Sinewave?

 

[Handy Andy]

Ok, I replaced C63, C64, and C83. C64 was reverse polarized according to the schematic, and the silkscreen on the board is incorrect. I put the new one in per the schematic, which shows negative to pin 18 of IC2.

No dice. Still 7.35 VDC on TP2.

Ok, you really should have stayed with the silkscreen outline. That may be the problem.

The silkscreen is the MOST recent version the Board has to use - for the date of it's manufacture. It sounds crazy but when you look back at the time line and how they put these boards together - they populated a lot of these by hand. In a way, they had their hands full - literally - with parts they hand to hand insert even though automation for much of the board was done - they still had stuff to "stuff in there" by hand when the robots were done injecting all those parts...

This 2.2uF x 2 filter is a unique one, for the PLL loop requires a good quality signal so they used heavy capacitance but most places don't make 1.1uF caps or thereabouts in monolithic or non-polarized forms. So the effort Uniden, Cobra, Realistic - amongst others...was to design a "Back to back" cap design with a resistor in-between to make the filter do what they wanted.

So follow the outline - that Silkscreen, for in our reality; it is the latest revisions and update to their board at the date of manufacture (Your Board Number inclusive).

My own Dog-Eared copy of 810e...

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For proof? If you go back to the Pro810e or the PC122XL, they follow what is above - but get out an older TRC-453 from the Service Manual - someone "corrected" an otherwise properly oriented cap thinking they were doing it right... - they show one cap polarity wrong, use your silkscreen. They did this too and one of my older pages describes one of the places - the Driver - where Realistic and Uniden took different routes with their capacitance use and overlaid a cap across the Base to Emitter Lead on the Realistic Driver, but not on Uniden - they used another approach so you had to remember the boards and they are NOT the same as all the others.

TRC-465 - SIMILAR TO but not the EXACT same as - a PC-122XL...

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Redo the cap layout - follow silkscreen, use the graphics PHOTO set above to help! That was a working PC-122 when I did up the docs for CB Tricks back then. You'll see the Caps CATHODE are "back to back" so the schematic was done in their error - The Plus side or non-banded side - faces outwards in this loop - so Positive to PLL Pin 18 and Positive To PLL Pin 19 - for this filter to work - it has to pass RF not smooth it - which the series aligned by polarity might do which makes the PLL not to seem to fire up.

In going back to my research, I see the error - the Schematic used showing that - is from a TRC-453 - which is one of many errors I've found in the PC-122 / TRC-453 / TRC-465 layouts. So in using that older Graphic I see my own error and goof...

Here's the TRC-453 BOARD - they revised THE SILKSCREEN! See below...


So again PLEASE FOLLOW the Silkscreen - they did, so you should too. The above is a 1985 radio - TRC-453 line. They even got the polarity of the caps the same way...

Also - MAKE SURE YOU HAVE 5 VOLTS at D36 and PLL Pin 11 and Pin 7!

If you don't, the PLL won't work...even though you have a channel display - it is INDEPENDENT of the PLL programming Pin Logic Truth Table...a separate system on the Channel Selector assembly.

Sorry about this...

 

[WECSOG]

Ok, I'll put a new one in there according to the silkscreen. Thanks!

 

[Handy Andy]

Other stuff to help, at least if my PC gets hit with a Virii - or whatever - and takes out the HD you have this...

During the time that CB Tricks was up, I was also building up my own "troubleshooting guide" that the References page was to expand into.

Like more of a region by region section by section overview of areas and changes that the PC and TRC models of this board modified into and then once the TRC-485 hit, - the radio took off in a vastly different direction and we wound up with the Bearcat series like the 980

But they (Uniden and Realistic) never went further with the design into a full din style radio - although McKinley and Lincoln and other "models" did show up. They were not like their predecessor.

We lost radios with Chassis like the Grant XL and Jackson, they just never went beyond the 1990's - sad to see that happen but understandably so with Market drive and people forcing our own jobs to build and make these radios further overseas - we lost our ability to keep a toehold on the way and means to make these older classic designs that are still in use today...

REVISED Schematic Layout showing Caps correctly oriented...


Pink showing Power supply feed as well...

PC-122 - when using the 2312 Final - needed paralleled caps to offset an admittance issue...


Note the uses of C202, R202 and D49 (In-between Final and Driver) - Asymmetry mod to offset AB clipping problem by providing more Bias power into Class A to improve the distortion values...

And now for some letdowns and Disparities...




This is a TRC-465 board - note the LAYOUT does change...

TRC-465 and PC-122 Similarities...




Although not a big deal - they do have their differences...so even with the above, and those small value changes in Resistor and caps, they are functionally pretty much alike - although I do say that with some reservation...

Will add more as time and wife permits...

 

[brandon7861]

@Handy Andy I remembered this thread from a while back and had to come back and find it. I am currently working on a project digging into what remains of the CBTricks site. I knew you had a power enhancement document on the CBT Member Publications section, but I also found another section that is not so easy to find from the CBTricks mirror titled "PC-122XL - in HD". I still cannot find where it was originally linked to from the CBT main page or how it got into my mirror outside of the members folder area, but somehow, it is there.

I saw in an earlier post you metioned working on something on CBT regarding this radio but didn't post that stuff here, so I assume you may have lost it when the site went down. It's not lost.

 

[Handy Andy]

@brandon7861 - Thank you for finding it.

I've kept a copy for myself and what is left of CBT and even some of the older threads saved off as "MHT" snapshots to offer help when I get lost.

Only now, I get more lost in the memories behind the MHT files so the task I wanted to perform was already covered by several posters ago before I even typed up the response.

*sigh*

You have to realize it's from a time long ago that when the world was simpler and Nextel was running Races to promote the 2-way features of their new system and that price tag to go along with it, and #3 was zooming around the racetrack ...

Why the mention of the Races? Because of Nextel and the technology behind it, CB became more of a Gentleman's game of chess and checkers - there was no longer the need to drive the market with fancy faceplates of shiny Mylar and the poorly designed IF vertical card strips that replaced the older more-stringent IF cans

As technology moved on, some liked the newer stuff so I had to scramble and learn the new ways of thinking and designing - only to get to a point in life where the stuff that built those radios, we lost to China, and is now irreparably lost - period. Only the spare parts bins and dust bunnies know of where the remainder of those parts are.

Gone are the days of radios like that - small compact and made with features with the most minimalist of parts possible and yet provide stable results from they day it was made and beyond. Their birth date - now closer to 50+ years of technology from back then, are still in operation. Amazingly - compare that to even radios of several months ago, are already failing in their stock form and their parts to fix them are even more unobtainium that what Uniden had for the PC-series

So I'm glad someone remembers those days - for now, social media has gotten to a point where your kids are no longer gathering around the radio to listen for friends and family on their trips to and fro and tasks that made radio an imaginary place of fun and drama. That is left to their phones.

And to think people pay for streaming and cable entertainment - when someone would play the local ball game over a channel just so others could hear it as "background" to keep out the skip static and hiss. Yet weak enough not to intrude - and let their loved ones call out and let the channel moms know where their Husbands were at

So when I look at those pages I see my history, some wonderful, some painful - some just downright fun. But it's a snapshot of a time frame - like that of a photograph and when Bennie had to pull the plug, so went that effort too.

I thank you and the others here, in the Forums for putting up with a guy like me, someone once said I was like a ADHD kid out here trying to help others fix radios. Well, in a way sometimes my efforts helped and fixed it and now it works, other times it didn't, and oftentimes we learn a little more about ourselves in the process.

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I'm still here.