17 Oct 2014 - Working on an FT301 that someone dropped off at my place up
here in Elliot Lake, ON. Canada. My qth is off of Hiway 17 by about 30 km to the
north. This is the Trans-Canada Hiway in the section between Sudbury and Sault
Ste. Marie Ontario. --> I'm a little off the beaten path and I am in what is called
Northern Ontario..(BUT) -- Ontario is a really big place and in actual fact, I am not
really all that far North. Anyways..a fellow dropped this rig off for repair. I gave
him a $60 estimate on labour. I work at $10 per hour. This is an INTERMITTENT
FAULT! -- The operator will be transmitting and suddenly the RF POWER OUTPUT
will drop down to 10 watts or sometimes much lower. -- IF the operator then
takes a rubber mallet and gives the heatsink a sharp and significant bump..the
radio will return to normal again.
Right now..I find .. it usually happens after the radio is warm and has been
transmitting for awhile.
hamelectronicsmagazine.com/earlandrews.com - since 2005

This is a free on-line hobby magazine written by Earl Andrews
VE3AB and is available to anyone. I pay for the web sites by
selling parts (mostly solid state transistors and other discrete
components).
I also do some repairs to older solid state gear that people
drop off or mail in to me. I work at a hobby rate of $10 per hour
and I often CAP the repair cost at what I think would be fair.
Afterall.. these are old radios and they may not be worth it to fix
if the repair costs for labour were more than maybe $50 to $70
or so. Parts-- I have pretty well all the parts and I sell them
pretty cheap actually. I have plenty of spare boards and knobs
and chasis parts. The only thing I am a little short on is parts
like the FINAL AMP TRANSISTORS and maybe the special bias
transistor FOR THE finals. I have plenty of DRIVER transistors
and other stuff here in my shop (large basement shop).
WRITE ME: this email (LINK HERE).. AND I can probably help you.
I dont have a rubber hammer..so I improvised and took a short piece of 2 by 4 wood and made a bit of a cushion out of an old rag. I didnt want
to scratch or mark the back of the heatsink when I give it a good little whack when the rig output falls off.

This whacking the rig may seem like something you might see in an old movie or something..but ..in this case..it works like a charm. The owner
of the rig would like to have it fixed properly ..however !! -- Probably a good thing.
A Bird 43 wattmeter is used to monitor the power output of the FT301. As it turned out; I had to do a significant amount of transmitting (I
used CW mostly) into the dummy load in order to get the rig to start acting up. Intermittent problems like this can be difficult at times to
diagnose. You have to try and stimulate the circuit(s) to act up. Often..this is with heat or cold. With this particular FT301; heat when
transmitting for an extended period of time at say a 50-50 duty cycle seemed to bring on the problem.
It seemed that I would get the rig
heated up by transmitting for say a good 15 minutes or so on CW..then I would stop for a pause of a minute then when I tried to transmit
again..that is when the TRANSMIT POWER..
would only be a couple of watts or so. I found (when the BOOSTER UNIT was external to the
radio (detached in test mode) -- I would not have to "hit" the back of the booster to get it going again. Often it would just come back on
again on its own ..(not long after it cut out).

I didnt want to over do the heat aspect. Things can get overheated and perhaps a type of Thermal Runaway situation could crop up and
then smoke could occur. I DON'T HAVE ANY SPARE FINAL TRANSISTORS FOR THE FT301. They don't show up at flea markets and if they
do..they are quickly gobbled up!
Above.. I disconnected the Booster and ran the rig
at the 10 watt level for some testing to see if the
rig would act up at the 10 watt level.
The rig did not act up under this condition and I
have pretty well concluded that the BOOSTER or
perhaps some circuitry that powers the Booster..is
to blame. SO I MOVED ON TO REMOVING THE
BOOSTER PHYSICALLY FROM THE RADIO AND
USING MY TEST WIRE HARNESS -- I OPERATED THE
BOOSTER WITH SEPARATION FROM THE MAIN
TRANSCEIVER.
Now Im going to go to work on the Booster Unit. I figure
that is the most likely problem circuit.
I started using some contact cleaner on the wire wound 10
ohm Rheostat. The Rheostat is set at the half way mark (5
ohms) in my other BOOSTER UNITS and it is in this one as
well. I thought maybe a bad oxidized connection might be
at the wiper contact. So I sprayed and moved it back and
forth a bit.
Not sure how to exactly set up the BIAS. The manual is not
very specific about setting the Bias. Too much bias current
turning on the Transistors could cause overheating and
could be the problem.
I will be reading the manual to see if I can pick out any
methods to adjust the BIAS.

Another possible problem could be the capacitors. I did
replace the three gray capacitors in the upper right hand
corner of the picture. I checked the ESR of the capacitors
and they were quite OK but I replaced them anyways while I
was at it. Many hams are re-capping older radios. There is a
fellow on Ebay selling Re-capping kits and one of his kits is
for the FT-301.

SEE SOME OF MY NOTES BELOW ON CAPACITORS. SOME
OF THE NEW ELECTROLYTICS (CHEAP ONES ESPECIALLY
ARE MUCH WORSE THAN THE OLD ORIGINAL CAPACITORS
IN THE 1970s and 1980s radios !
The Final Amplifier Booster Unit was run fairly hard on CW for about 15 minutes and NO problems and no output power fluctations..BUT.. I then
put the cover on the unit and the power then dropped down to almost zero when I started sending CW again. The heat built up and seemed to
trigger the POWER OUTAGE problem.
The upper ferrite transformer (the bigger one) did seem to heat significantly and (perhaps) a saturation problem of the ferrite might have
something to do with the problem of the power cutting out.
Another thing that might be a problem is not enough heatsink compound under the transistors or heatskink compound that has dried out.
Note on RE-CAPPING. Watch out for bad capacitors. These JAKEC 4.7 uf at 50 Volt measured 5.0 ohms ESR which is far far more than a new
capacitor should be! -- When doing repairs.. I check the ESR of the new capacitors because there are some bad ones being manufactured
nowadays.  

My own experience with the FT301s and Ten Tec Argonaut 509 and similar vintage rigs is that they really don't need re-capping (YET) (AS A
GENERAL RULE).
PROBLEM SOLVED: 19 Oct 2014 -- A closer examination (visual) revealed the FINAL
TRANSITORS (base leads) WERE NOT SOLDERED AT ALL!! -- Its a wonder the radio
worked so well!!! Actually..one base lead had a wee bit of solder but the other one was dry.
Perhaps the fellow doing the soldering got distracted and when went back to the assembly
or repair job.. he/she forgot to finish the job!
One lead I just peeled off the board (the far one) and there was no solder at all holding it down. The other one pictured above..(closer to the
viewer) .. was maybe soldered just a wee bit but certainly not properly.
I was guilty of skipping an important step in troubleshooting...DO A THOROUGH -- VISUAL -- INSPECTION to turn up something obvious.
Anyways..no harm done. I am retired now and I don't watch the clock all that closely. Certainly you don't expect that the transistors were not
soldered properly in place. The rig was working (for the most part) afterall !  -- Sometimes you have to expect the unexpected.
MORE TO BE ADDED TO THIS ARTICLE SOON..
73 Earl VE3AB

LINK
to my home page www.earlandrews.com or
www.ham
electronicsmagazine.com (mirror sites) est. 2005
NOW to solve the next problem with this rig: when the radio is being operated and the operator
switches from say: USB to CW using the mode switch..the radio transmits a brief transient
carrier that can be picked up with another receiver. There should be no transmitted signals
when the MODE SWITCH is moved to another mode !
While I was at it. I checked some other new or relatively new electrolytic
capacitors in my junkbox. The CHONG ones in the picture tested at 2.5 ohms
ESR (Equivalent Series Resistance). Too high ! MUCH too high for new
capacitors. JUNK ! -- I have ordered more electrolytics now and I am
specifically ordering LOW ESR higher quality caps and they should be in
soon.

SOME OTHER CHONG CAPACITORS DID TEST PRETTY GOOD HOWEVER. I
ONLY USE THESE CHEAPIES ON MY OWN EXPERIMENTAL CIRCUITS.
I have
ordered in GOOD LOW ESR ELECTROLYTIC CAPACITORS AND I WILL BE
SELLING THEM TO EXPERIMENTERS AND TINKERERS.. just write me for
PARTS ..I sell very reasonable prices and low shipping charges too!
I cleaned the MODE Switch with a good quality contact cleaner.
I checked the diodes and took measurements on both my good
working FT301 and the one that had the problem with the mode
switch invoking transient brief transmission. I did discover one
bad .047 uf ceramic bypass capacitor on one of the control
lines in connection with the mode switch through analysis of
these measurements. SEE BELOW PICS
I have the luxury of having a good working FT301 at my disposal for
trouble-shooting. I can swap plug in circuit boards to diagnose problems
quickly and also I can make measurements on the good radio and compare
them to the measurements I make on the radio with fault(s).