|Something goes wrong..in a hurry!! a POP is heard and the rig no longer functions fully..what to do?
My suggestions on TROUBLESHOOTING. From a letter I very recently received concerning an
FT301 which quit on transmit. -- I felt this would make a good story!
Below: the final amplifier compartment of the FT301D. It detaches from the FT301 body. This
amplifer boosts the drive signal by about 10db or maybe a bit more. Sometimes the final
output transistors have an internal short and they burn out rather quickly. Also..this radio is
getting older. It is at the time when components start to die with age. The electrolytic
capacitors are particularly prone to going bad with age. Leaks develop (ESR losses and the
paste dries out). These things can be accelerated if the rig sits for years without power
being applied. When I was young and foolish..I bought an old (but nice) stereo tube receiver
with all vacuum tubes. Maybe about 15 tubes or so. I plugged it in and turned it on--BIG POP.
Opened the bottom lid and an electrolytic capacitor had blown up and there was a curly tail
trail of paper and other little bits around. --- Capacitors need to be conditioned. When
restoring older equipment. You should use a variac to bring the voltages up slowly. Older
gear being restored is often re-capped. Newer capacitors is one of the first steps to
bringing old gear to life. The FT301 is getting older and the electrolytic capacitors are good
candidates for a fresh new start.
Below is a photo of a PA stage that crapped out on me. I have to work on it one of these
days!!! IT OVERHEATED! - I highly suspect a PA transistor had an internal short. I will be lifting
the 2 RF transistors and testing them. IF BAD..I will have to find replacements. I will likely..at
the same time..re-cap this stage with new electrolytic capacitors.
Here is a magazine ad from the mid to late seventies. The FT301
was one of the early fully solid state radios of that era. Most
transceivers that were built in the mid to late 70s were still using
tubes for final ampllification. The driver tube was also very
common. The rest of the radio was all solid state however. The
FT101 series, TS520, 530, 820 and 830 are all built in this manner.
These old rigs are still popular today. There is a Yahoo Group
specifically for these older rigs and you can pick up ideas, files,
photos from the Yahoo group for your particular radio. The FT301
has two yahoo groups..one under FT301 and one under Yaesu
FT301. A bit of needless duplication! The files and photos and
discussions are all relevant.
Ok Richard. I would start with downloading the 53 page shop manual. You can find
it on the fox tango web site or join the yahoo groups FT301 and Yaesu FT301..and
check the files section for it. The site DK mods is a good one to link up with. You
get a free download every 4 days of a manual or mod article.
Is your power supply still working? You can start with that. Even though the
receiver works..maybe you lost regulation or a filter capacitor and the radio will
appear to work fine but the voltage may not be properly regulated.
Another possibility is in the final transistor stage. You can physically remove the
big heatsink. Label the two coax connections as to which one is the top one.
Then you can bridge the upper and lower RF connector on the back of the FT301-
without the final stage on the radio. You need a short coax with two bnc
connectors. Then you now have the 10 watt driver stage as the working stage for
the radio complete with the filters. Then you should test on transmit to see if you
get any powr outuput. -- Should be about 5 to 10 watts on each band approximately.
If the rig now works on transmit and receive..you pretty well know it is in the Final
stage. -- Possibly one or both finals a possiblitly of damage.
I dont have any spare finals in my parts collection..but I have all the other parts. Try
those ideas out to start richard and keep me posted. 73 earl ve3ab
Subject: re ft 301
Was just looking through the web and saw your pages on the ft 301. The other day I was using the ft 301 and had a bout a 2 minute over and
almost towards the end of the qso there a was bang and I lost transmit. Any ideas or can you tell me where to start looking please. RX still
works, lights all work.
Rich (from VK2 land)
This is not all that bad a situation and would make for a good trouble shooting repair (if done correctly). First of all..the rig was working before
and then ..suddently something went wrong. Well..at least the troubleshooter knows the rig was working before properly. Sometimes you buy
a broken rig and have no idea what has been done to it..or what happened to it. First of all. IF THIS HAD HAPPENED TO ME..the ideal thing to
do is shut the rig off. number one. NUMBER 2..think about it. FEEL around..see if the heatsink for the final transistors is overly warm?? USE
your sense of smell and touch. Look for a damaged burned component. Feel around for heat. NOTE: with solid state 12 v gear..no problems to
feel around circuitry..but with tube equipment..be careful. Lethal voltages present.
I have 4 FT301 radios in my collection. I bought one that was in real bad shape. I use it for my parts pulling. ONE rig I had developed a problem
one day and I had it on receive..and I could smell something funny and I narrowed it down to the FT301 which was on and I was monitoring a
frequency in the background while I worked. IT WAS HOT. The back end Final Output heatsink was very hot. That rig no longer works and
delivers 100 watts. I have set the final output compartment to the side now. I dont have final output transistors to replace the ones that
shorted out. SO FINAL TRANSISTORS sometimes develop internal shorts and burn out. YOU SHOULD have an appropriate fuse that will blow
when the transistors do this. MAYBE THE ideal radio would leave the power disconnected to the final transistors when you are using it as a
receiver only. The old FT101 had a switch that you could remove power to the final tubes when just using it for receive.
I no longer leave the radio ON when I go upstairs or away from the shack for long periods of time. That way..if something goes wrong..I will be
right there to turn the power off. With older gear..ie 25 years old or older..this is not a bad idea. I have had a couple of rigs go bad when I was
not around to shut them off. Overheating occurred. NOT A GOOD IDEA WITH OLDER GEAR to leave them unattended.
WHEN ..I GO TO REPAIR THE FINAL OUTPUT 100 WATT MODULE..I will be recapping the circuit with new capacitors and look for other problems.
I am going to try and buy some low priced transistors at flea markets this spring and summer. MOST OF THE PARTS I sell (on the side) are low
power QRP and small signal transistors and the like. MRF454 and MRF455 and similar 50 watt transistors are very expensive and rather hard
to buy surplus. They get snapped up pretty quickly by hams who want to have spare finals.
BELOW is the email response I sent back to Rich. I thought it would be of interest to other hams who might have run into a problem
something like this. AT least with the FT301..it is fairly easy to work on. The components are still widely available. I keep plenty of spares and I
sell them (the odd time) to other hams. Sometimes..if you are really serious about certain pieces of equipment (sentimental pieces like your
first rig ect) then buy a spare parts rig and have two of them. My first receiver was a Heath HR10B. I keep one around for sentimental reasons.
|Additional commentary by me
The first step in troubleshooting is DC analysis.
THE POWER SUPPLY SHOULD BE CHECKED OUT FIRST. MAYBE
THAT POP WAS IN THE POWER SUPPLY. -- To check a power
supply..you need to measure the voltage under load to see if it
holds its regulation. YOU need a load resistance of about 13
ohms to measure 1 AMP and you need a good wattage resistor of
about 10 watts or better.
USE your Volt Ohm meter and measure the voltage before adding
the load resistor then after. For a light load of 1 AMP on a 20 amp
power supply ..you should see very little voltage drop across the
YOu need a higher wattage resistance and lower resistance for a
10 amp load. I saw a web site by Roy Butler a fellow from VK land
who built a load resistor from common insulated wire. If you use
enough wire you can build a low resistance load. I would fuse it
with a 15 amp fuse when experimenting. That way you wont melt
IF the power supply is OK..then you continue with a DC analysis
of the radio itself..BUT ..BEFORE..GOING ANY FURTHUR..I would
practice a key rule of trouble shooting..and that is
DIVIDE AND CONQUER.
--To narrow down the problem: remove whatever parts you
suspect as being bad or highly suspect and see WHAT DOES
WORK and keep that going and separate.
Remove from the circuitry of the radio..a potential cause of high
current drainage and problems..I would remove the 100 watt
power amplifer stage when working on the FT301. With other
radios..they high power amplification stage is very often HARD
WIRED into the circuitry. WITH THE FT301, the Power Output stage
is plug in with connectors and can be easily separated. DIVIDE
The 100 watt PA stage is a prime suspect for problems when the
transmitter goes south and you hear a POP!!! With the FT301..the
PA stage is handy to remove. There are connectors and you can
jumper the two RF connectors on the FT301 back plate and run
the rig as a qrp rig with only the driver stage.
NOW..CONTINUE DC ANALYSIS with the FT301.
DC analysis is the first step in troubleshooting circuitry. If it
doesnt have the correct DC voltages in place..to turn on the
diodes and transistors and have them "sit" at their operating
voltages ready to amplify or pass AC signals ie AUDIO and/or
RF..then the circuitry wont work or they may work with alot of
See the schematic from the FT301 "shop manual" and
explanation of the circuitry below (in a rather simpistic form). I am
an ordinary technician..hands on..and I don't know the math all
that well or the physics behind the goings on to any degree of
I plan to rebuild this PA stage..when I scrounge some final transistors for a cheap price. I
will be asking around at flea markets for new old surplus! Another option..for now
anyways..use the FT301 QRP..I operate QRP CW contests and maybe turn the 301 into a qrp
10 watt maximum rig. Yaesu did make a qrp version of the FT301. To do this..you bridge the
two BNC connectors at the back of the rig. The 100 watt rated LOW PASS filter network then
works fine with the 10 watts. Kenwood also made QRP versions of the TS120 and TS130.
|MY RESPONSE TO Richards email.
MY other FT301 pages/articles feature working with the FT301 circuitry. The
circuit cards are plug in and have discrete semiconductors and components and
some ICs as well. They are all pretty much still available. I have spares and
sometimes you can find them on ebay (somewhat pricey) and at places like Dans
Small Parts in USA(only) and W8DIZ and other qrp suppliers sell some parts that
work in these older rigs.
Alot has been written about the satisfaction of homebrewing radios from scratch.
I know one ham who used to say: that the transceivers are maybe a bit too
complex to homebrew..but a ham should still be able to work on and trouble
shoot his own equipment.
I say..there is nothing wrong with being an appliance operator. We all drive cars.
We all need mechanics to work on them and even the mechanics need mechanics
to help them with their repairs.
I say..THIS IS A HOBBY. FOR ME..WORKING ON THIS OLD STUFF IS WHAT I DO
..BECAUSE I AM FAMILIAR WITH IT AND THE PARTS AND THE CIRCUITRY.
YOU HAVE TO FIND your way and enjoy what you are doing. I lose myself when I
write and make web pages and when Im down in the shack working on
problems..yes..at times I find it frustrating..and sometimes..I walk away from
trouble shooting some darned old thing that went wrong..but I can return to it
whenever Im in the mood or better mood and finish it off.
Is it plug and play or plug and pray or pray for another day or get away..don't let
anyone lead you astray..find yourself a rainbow and sit on it and soak up the
colors in your soul.
tally ho..73 earl ve3ab
Transistors are 'biased' with DC voltages that are appropriate for the size of the signals they are going to amplify they are "enabled" to operate and function
by control voltages.
TX13.5 V appears on pin 7 of the card edge connector (underside of the FT301) on the filter unit board. The XFs are crystal filters and there will be actual
crystal filters or spots for placing the crystal filters in place. The RX IF..Receiver IF frequency is about 9 mhz which is a common HF radio IF frequency. IF you
want to see if your IF stage is working..just sweep around an antenna analyser around 9 mhz and you should hear a loud dirty signal. If you dont have an
antenna analyser or signal generator..you could build a crystal oscillator to generate a 9 mhz test signal. I have a very simple NAND gate oscillator that I use
for crystal checking.
TX13.5 will appear on pin 7 when the transmitter is keyed. RX13.5 (pin 3 should appear when the radio is in receive mode). RX11V is 11volts when the receiver
is in receive mode. D308 is an 11 volt zener and holds the voltage at 11 volts. If the RX11 line is 13.5 volts or 0 volts ..it could mean that the zener is either
open circuit or shorted out. Zeners are a bit noisy sometimes and I had one that was generating alot of hash. Zeners are pretty cheap to buy from QRP
suppliers like Dans Small parts or Goldmine electronics or Tayda in Taiwan. I sell some as well..in fact..I sell one at a time if you need one.
TX13.5 is a voltage which activates and turns on D307 and the other diodes in the circuitry to allow ac signals to be present at the Crystal filters in Transmit
RX 13.5 is a receive only DC voltage present only when radio is in receive mode. TX 13.5 is a Transmit DC voltage present only when radio in transmit mode.
and if theyer is a voltage indicator such as 13.5 V (with no TX or T or RX or R beside it) ..it means the DC voltage is always present.
Anyways..most of the times in my trouble shooting FT301s..the DC control voltages are usually good but they are so easy to check and one is better to confirm
they are present before..digging down furthur into the "weeds" to see what could be wrong.
DC analysis is the first step to troubleshooting in most cases. You have to have the DC voltages present in order for the radio to work. So..to recap the
DIVIDE AND CONQUER SCENERIO so far: SYMPTOM: a sudden bang and loss of transmit. Radio still works on receive. Ok ..well start the DIVIDE AND
CONQUER procedure. REMOVE the heatsink with the FINAL AMPLIFIER circuitry. With the FT301..this is pretty easy to do. Now we test the lower level
First see if the 10 watt stage works. Then go back into the circuit to see if the 1 watt stage works. I say 1 watt as a broad approximation. It may be more or
less than 1 watt. It is the stage that delivers the drive level to the 10 watt stage.
A good CLEAR large schematic is nice to have when following and tracing the rf paths. I noticed in one of the two Yahoo Groups for the FT301, in the files
section..someone downloaded a CLEAR EASIER TO READ schematic diagram of the Ft301. You can print this out in secions as necesary and tape them
together to make a large schematic. This together with the 53 page shop manual..(also found pdf form in these yahoo groups) will help in tracing things
I will be writing more on this article a little later on with some more pictures and maybe Rich will write back with an update....for now..these ideas should
get you started..73 earl ve3ab (April 14 2011)
Very recently..a fellow emailed me from W5 land in USA and he had low power output on all bands. I wrote up some general advice and I suggested some
ways to increase the power output and he was sucessful in getting the full power output on all bands (except for 10 meters) where the output is quite
low. I gave him some futhur suggestions to try. HERE is a link to that page with pictures and information on the LOW POWER OUTPUT scenerio.
Is the FT301 now a candidate for "re-capping"??? I'd say quite possibly!!
Above Pictured: the 10 watt RF driver stage. Note the small grey electrolytic
capacitors. When older rigs/boatanchors are restored..often the first step in the
restoration process is "recapping". In the case of Richards rig that when "POP"
on him when he was transmitting..I don't know enough about the situation..but
lets just say for example ..that it WAS an electrolytic capacitor that gave out and
popped or self destructed.
In that case..I would say..the whole radio could be re-capped. ME myself..I havent
done that to any of my older solid state rigs from the late 70s and the 1980s.
I seen one fellow on ebay who was selling "re-capping kits" for transceivers and
one of them was for the FT301.
Above a picture of the bottom side of the FT301. 2 larger grey electrolytic
capacitors are pictured. These would be easy to replace and when you do buy a
modern replacement capacitor..you will probably find they are smaller in size.
Also seen in this picture are the blue circuit card connectors. Each terminal is
numbered and the number appears on the schematic diagrams in the shop
manual for each card. Makes trouble shooting fairly easy. AN EXTENDER CARD
FOR THE CIRCUIT BOARD in order to make measurements on the circuit board
when it is "active" and working is a good idea. Below is a picture of an extender
card for these older radios with plug in circuit cards.
A circuit card extender..extender card is a good idea if you are troubleshooting
this radio and other radios with plug in cards. It gets the card up away from the
inner chassis and allows you to perform measurements while the radio is on and
the circuit is active. I plan to build an extender card in the near future.
|Extender boards are a big help in
troubleshooting. I have created a
new page with some info click
here concerning how to make
PARTS SUBSTITUTION NOTES
Q302 is a 2SK19GR. This is a very common FET used in FT301s, FT101s and other radios. I just checked ebay and I seen them listed for $9.95 each.
IF it were me ...and I had to replace Q302..I would not pay $10 plus shipping for a JFET. I would substitute parts.
IMPORTANT NOTE ABOUT PART NUMBERS.. if the part has K19GR..chances are its full part number is 2SK19GR and similarly for the 2SC series of
transistors some transistor marked with C1969 will be 2SC1969.. it is a convention. I'm pretty sure these are japanese transistors and that
convention is often followed. The NTE (aftermarket parts) books I have will have a cross reference for 2SK19GR as well as K19GR and they cross
reference to the same NTE aftermarket part. NTE and ECG used the same aftermarket simplified part numbers. I keep a few ECG or NTE books by
the work bench for looking up parts.
Analysing the circuit..Q302 is used in the receive mode. The output of this FET goes through one of the crystal filters and is driven by Q301. I
would take the key characteristics such as transconductance, power dissipation, ect and I would find some other FET such as (maybe) a 2n4416a
and I would substitute it in. If I had to transpose leads to get the pin out right..I would use a bit of different color heat shrink on each lead to make
it stand out and I would put a small label with a little note of some sort on the circuit board..maybe up on the metal tab for the circuit board (lots of
room there). So if someone buys your rig..THEY KNOW you did a modification. --> This is not a good recommended method for servicing equipment.
Private industry would certainly frown upon such a NON CONFORMIST action. But we are amateurs. BUT..we must think ahead and must find a way
to document modifications in such a way as they cannot be missed..even if the manual goes missing. This style of modification..where you dont use
a "drop in replacement" but rather..in effect..modify the physical layout (even just a wee bit) MUST BE DOCUMENTED. ITS A GOOD IDEA. WHO
KNOWS WHAT THE FUTURE HOLDS..YOU MIGHT GET HIT BY A CAR AND YOUR SPOUSE WILL HAVE TO SELL THE RIG. TAKE AN EXTRA FEW MINUTES
AND LABEL AND DOCUMENT THE MODIFICATION SO IT CANNOT BE MISSED OR MISREAD. PUT A GOOD NOTE IN THE MANUAL FOR THE RIG AS WELL.