# CB transceivers

Discussion in 'Electronic Repair' started by William Sommerwerck, Dec 17, 2009.

1. ### William SommerwerckGuest

Don't you have a working receiver you could first use to find which are
transmitting?

2. ### D YuniskisGuest

I chuckled to myself as I pondered this problem -- it
reminded me of similar math/logic problems as a kid
that also seemed "unsolvable" (on the surface). So, I'm
looking for a similar twist to solve this one...

I have several rescued CB transceivers of indeterminate
quality. Since I have no idea what portions (Tx vs Rx)
of any of them work and which don't, how should I go about
sorting those that are keepers from those that belong in
the recycle bin?

Obviously, the first pass is to try Tx on each and see if
*any* of them receive. This tells me I have one good XMTR
and one good RCVR. From that, I can deduce the status
of all the other Tx and Rx.

But, what if none of these combinations work? I would
assume this would be bad Tx in all (as I would think it
easier to fry the output stage than *all* of the receivers)

Any other tricks I could try?

3. ### D YuniskisGuest

No, that's what makes it so similar to those math puzzles...
how to get information without having any!

(I think turn them all on and individually key them one
at a time is the best place to start. If *none* of
them appear to work then either they all have bad Tx or
they all have bad Rx. In either case, they are all *bad*
:-/ )

Make TWO.

5. ### Clint SharpGuest

Not that difficult in practice, if you have a failed TX PA stage (most
likely) it will still produce enough signal to open up a working RX.
Likely you can also watch the meter on the TX, with a bad PA it will
still move up a little. If it drops to zero then it's likely that the
VCO is out of lock. There is enough repair info on the web that you can
solve most problems given enough patience and a little skill.

6. ### D YuniskisGuest

They are all handhelds so each has a telescopic whip antenna.
However, we are quite far from any large highways so picking
up any trucking traffic, for example, wouldn't be possible
(it's a 30 minute drive to the nearest interstate highway)
The problem is you need *two* working receivers. I.e., if the
receiver on unit A works, the only way to test the transmitter
on unit A is with a working "unit B" (?)
All of the sets appear to be highly integrated. Digital PLLs,
etc. I wanted a quick way to cull the "dead" from the "undead"
and then decide if any were worth repairing. This isn't
a hobby, etc. Rather, just deciding if any are worth tossing in
my bugout bag or if they should all just go in the "trash".
I won't start looking until I know which units are worth
my attention. I think I have six different units here
each of indeterminate quality... (I would like to get those
that don't work and aren't worth my attention out of here
to cut down on clutter, etc.)

7. ### William SommerwerckGuest

I won't start looking until I know which units are worth
In the time you spent on this e-mail, you could have brute-force tested all
the units.

8. ### D YuniskisGuest

.... and LEARNED absolutely *nothing*! Like, "Gee, do I have to
screw this antenna on *before* keying the transmitter? After
all, the receiving unit is just a foot away... why bother
putting the antenna on?"

How would that have helped me sort through the various HAM kit
waiting to be tested after these??

Perhaps I should just have discarded the whole assortment?

I am touched by your apparent concern for how I spend my time! ;-)

9. ### William SommerwerckGuest

I can be rather blunt, Mr. Yuniskis.

I've learned -- from my own experience, as well as others' -- that people
often waste a huge amount of time planning to do something, instead of just
jumping in and doing it. *

In this case, planning would have had little effect. You should have hooked
a suitable transmitting antenna to one unit, and a short wire to another,
and seen what happened.

The Amateur equipment is another matter. You have the SW bands to see
whether the receiver works. Once you find a working receiver, you can
proceed from there.

* I've been servicing electornic equipment on and off for 50+ years. (In the
past 20 years, more off than on.) There are two approaches to service --
figuring out exactly what's wrong, or simply getting the item working again
by any means. As an intellectual, my natural inclination is to the former --
but you can waste huge amounts of time. More often, the "try anything"
approach is more efficient.

10. ### D YuniskisGuest

Herein lies the difference! I've been designing equipment
(medical devices, computer peripherals, gaming machines, etc.)
for the past 30+ years. There, you learn that NOT planning
(i.e., "jumping in and doing it") ends up wasting a LOT of
time and usually leaves you chasing after a bad design strategy
that you would have figured out had you only thought it through
*before* starting. While a repair might require a few TENS
of hours, a design may require a few THOUSAND hours. Hence
the folly of not planning.

I took your advice -- since there were no other hints that
might have saved me appreciable time (though I now recall that
one of my older PC's could have been used as a crude signal
source to at least get a rough idea which receivers showed
signs of life).

Had I had 50 or 60 "batteries", this would have been much
easier -- I could have installed batteries in each unit,
set squelch to minimum and keyed one unit at a time
while listening to see which, if any, of the other units
after each test (I had enough batteries for one unit and
an AC adapter that worked on only some of the units -- so
when testing certain pairs).

I made a chart showing each (Tx, Rx) pair and the results of
the first pass. From that, I was able to rule out two sets
that didn't look like they would ever be worth pursuing.
The others I ran through the same routine again -- this time
borrowing some C-Zn cells so I could eliminate the battery
eliminator (it seemed to cause 60 Hz noise on some of the
units of an amplitude great enough to swamp the transmission).

I *think* I now have four likely candidates to do extended tests
with. I'll put them in the car for the next time I am close
enough to the interstate to pick up some traffic there.

It took me the better part of 2 hours to test each combination
of tranceivers (6 units means 30 combinations -- actually,
they are permutations as order is significant). Considerably
longer than the time spent on these USENET posts... :-/

In hindsight, "planning" would have had me purchase a bulk
package of batteries at Costco and testing them en masse.