Palomar Kachina - A photo essay of my learning the circuitry and
going through the hardware inch by inch and component by
component. by Earl VE3AB
Testing the crystal oscillator for 28.000 mhz. For 28 mhz the crystal controlled
oscilator generates 35 mhz which is then added to the VFO frequency (5 mhz
vfo for  28 mhz) and the resulting 40 mhz signal is then mixed with a 12 mhz IF
which when subtracted results in 28 mhz operation frequency.

The Vfo will actually tune a whole Mhz of each band. ie 28 to 29 mhz.

This radio will also tune 26 mhz to 27 mhz and 27 mhz to 28 mhz. The CB bands!
It is not marked on the band switch shown above..but you go down one or two
clicks and the bands are there!
This Kachina was optimized for the CB bands (I found out later). The transmit
power (via tuned circuits) was maximum on the CB bands then dropped off
in the 28 and 29 mhz allocations.
Later in the process..I did a tune up of the radio on transmit to change this for
28 to 29 mhz optimization. The CB power output dropped to about 1/2 of what it
was as a result of my re-tuning.
12 mhz IF frequency is measured at one of the points below pictured on the edge connector for the circuit board.
Wire loop near the shielded IF can. That is a test point for the 40 mhz injection frequency. WIRE
LOOP TEST POINT.

I call this an injection frequency. I guess that is the correct terminology.

Doesnt matter that much: bottom line: the receive level (audio) is way down.

I have suspicions at this point of a few possible problems;

1) the main AF amplifier IC part nr. (on the schematic) UA706. I managed to find some of these
(subsitutes:
TBA641BX1 AUDIO AMPLIFIER IC 2,2W (9V) 641 UHER uA706 NEU NEW (on ebay..shown left)
I bought 3. One for this Kachina and 2 extras for the shop. I had to line all the leads up to dual in line
format and the heatsink was not the same as the original but it fit in the space on the radio and the
radio now works so Im happy.

I built  a homebrew extender card. The extender card allowed me to trace signals and gain access
to components for measurements and will allow me to inject audio or RF.


ooo
I AM KEEPING ALL MY NOTES and the notes on the schematics in case I ever have to work
on another Kachina.
THE Kachina on its side and in the back my HP Signal Generator (being used in this repair) and as well my HP Spectrum Analyser is in behind there as well. Above..testing
the heterodyne oscillator crystals. Measuring the Frequency and observing the wave forms.
Above: the IF signal being measured. WITH THIS RADIO: the IF
frequency and the BFO, VFO and all the proper signals are present. The
problem is (with the receive) the receive levels are down at least 40 db
from where they should be.
The INJ spot on the circuit card (below the WIRE LOOP TEST POINT) I marked it as INJ as
shown. 2 coax cables go from this point. This radio had been worked on previously. - I did not
try and remove messy looking cable/shields.. I just wanted to get the rig working again!
Above left-- after the etching process. I had to etch away the top part of the prototyping board so that the connector would not be shorting out.
To etch- I used a thick plastic bag and Ferric Chloride from Radio Shack and it took about 1/2 hour of time to etch away the materials. I would knead
the bag from time to time and I would heat the bag up (carefully) under a strong lamp. Heat speeds up the etching process. The used etchant was
drained off into the larger jar and is scheduled to go to hazardous waste depot in Elliot Lake.

I plan to use this method again to make circuit cards. It worked very well.
Bad Solder joints/Cold Solder Joints - a close visual inspection and a bit of picking away at
some wire leads will sometimes come up with some bad soldering. A couple of real bad ones
were found on this board I was examining closely.
LEFT PICTURED << BAD SOLDER JOINT <<<
This was a real bad solder joint. Not always do they stand
out visually like this one. I was sorting through the
components around the main audio amplifier IC (the one
with the integrated metal heatsink UA706  and I came
across a couple of bad joints.

I  was wondering why the lead was moving so much when I
put hand pressure on it. It was a very poor soldering job by
the looks of it and/or there might have been some oxide on
the component lead which did not allow a good bond.
Regardless. I cleaned the lead (a bit of scraping) then
soldered it firmly in place.

MY $10 per hour rate (and I dont go hard on people) allows
this kind of trouble shooting and rework for sentimental
pieces of electronics and/or..as in the case of this KACHINA
- RARE radios. I will be looking for more work like this (after
my summer vacation period).. in November of 2014.
Kachina on its side with the covers off. I found some information on a CB Tricks Web
site. That got me started.
The Kachina has plug in circuit boards (for the most part). This allows a trouble
shooter easier access to the board. I unplugged boards for a close visual
inspection. I found some bad solder joints when doing this. Also ..when checking
for faults..you can try and determine which part of the circuit might be failing. You
can then do a much closer visual inspection and then try measuring some of the
components..ie switching diodes. I found a bad switching diode using this method.
A DC analysis often comes first. The Kachina did not have a trouble shooting chart or voltage chart..so I just had to do an analysis as I went along.
I checked the Zener diode voltages and the 8 volt lines and the 13 volt lines and the switched lines ..ie 13 v during transmit condition and 13 volt
when on receive.
Below.. started checking the obvious signals that should be present..ie the overtone oscillator (heterodyne oscillator).
I used an oscilloscope and a frequency counter to trace and measure various signal
points on the radio.
Above: a 5 volt regulator IC. When ever you see a voltage regulator
IC..you can measure the voltage and make sure it is doing its job.
The 5 volts from this IC is for the LOGIC circuitry. IF this were my radio - I
would seriously consider putting in an additonal regulator ..say 8 volts to
step the 13 volts down to 5 more gradually.  A problem could occur where
if this 5 volt regulator shorts out..it might wipe out the logic circuitry.
The logic circuitry is old and might be expensive to get some of the older
chips.
This radio..(as do many radios) use switching diodes to switch in various circuits.
Here is a defective (shorted switching diode I found). There were no marking on the
diode and I didnt have the schematic or service manual (yet) (someone sent it to me
later in pdf format)..so I went ahead with a substitution. I used a common 1N914
diode in its place. It worked.
Test point where 40 mhz was measured..as below on the scope
HOMEBREW EXTENDER CARD WAS MADE FROM PARTS I have around here. I do have
many many parts! I sell them to here and there to help pay for shop supplies. So if you need
anything..especially an odd item.. I can have a look for you.
PAGE 2 OF THIS ARTICLE IS NOW BEING WRITTEN
(JULY 12-14) AND you can view it if you like..see the
LINK at the right ----------------------------------------->>>


73 EARL VE3AB
Left.. I hold the heavy duty plastic bag up to an LED type
floodlight (newer type of lamp). It does throw a good bit of
heat. Heating the etching liquid speeds up the process.

Next time I might use a cooking tray with hot water. Turned
out pretty good.

Another thing I want to try is enamel paint as the resist
etch and try making up a few circuit boards that way.
Here is the audio board. Audio circuitry at the right hand side. I checked the ESR of some
of these NIchicon VX(M) capacitors (the blue electrolytics) and they were all pretty good
readings. -- I have some of these as spares in my shop and I plan to buy more and sell
them (I sell parts too!) starting in the fall of 2014.
Left pictured: MC1350. Very common in ARRL
projects for many years and in many ham radio
transceivers both commercial and homebrew.

The nice thing about working on old radios is the
parts are quite often still available. Just check out
my big superlist of parts or ebay.com or kits and
parts dot com.

There are many places you can still buy these parts.

Sometimes..however..you come across old parts
that are discontinued and hard to get.

The UA706 audio amplifier IC was one of those
parts. Fortunately I bought a few from a source in
Germany. Price was $16.00 Canadian and postage
was $6.00

Worked great. -- HOWEVER.. IF THAT LISTING
FROM GERMANY WAS NOT ON EBAY..might have
been a different story.
Here I test one of the relays in the
radio.

If I would have had to replace this
relay..I would have been hard
pressed to find the original.

The original was made in USA and
there were no listings for this part.

It would not have been too hard to
adapt some other relay to the
circuit.

I have a couple of shoe boxes of
relays and some in bins.

I have some real nice Teledyne
high quality ones as well that could
have been adapted to the circuit.
Continued on
PAGE 2 >>>


CLICK HERE TO GO
TO PAGE 2 OF THE
KACHINA REPAIR.
UPDATED: 4 AUG 2014

www.earlandrews.com
www.ham
electronicsmagazine.com
(mirror sites) since 2005