[Yaesu] STU -- FT-101 6146 modification - DON'T DO IT !!

Carol L Maher w4clm.ham at juno.com
Thu Jun 12 02:26:05 EDT 2003

I just read your posting about modifying the FT-101E over to
6146 finals.  For God's sake man, DON'T DO IT.

Let me clarify for you why.   I have seen several rigs where this was
attempted, sockets changed, capacitors changed, tubes changed....
the whole works.   Ok fine.  Both rigs were never to be right again.
Understanding that a transceiver is just that,  part transmitter and part
receiver you can get circuits to react to each other by modifying
a circuit in one area of the rig, it can cause new problems
to show up in other areas of the transceiver. 
Ok, no problem understanding this here, I'm sure.
But with the final amplifier so closely tied to the receiver, as it is in

the FT-101 you are asking for some of the same problems that I noted
by experience that I have seen in other FT-101 transceivers
that were modified to the 6146.  

Let me back up, the FT-101 was designed around the 6JS6C sweep
tube as you well know.  I'd like to belive the engineers who designed
the rig knew far more about that rig then some joker writing an article
for QST and then modifying the rig after the fact.  The two rigs which I
saw modified to 6146 finals had very low output for starters.  They had
some output on 80 & 40 meters, 20, 15, 10 were about KAPUT.
Now that's only for starters.   What really  convinced  me just 
how bad this modification is was the fact that the receiver had birdies
and oscillations that were showing up all across the receivers dial in
spots up and down the bands.  ALL BANDS had problems.  
At first I just could not belive the finals would have such a dramatic
on the receiver, but keep in mind when the rig was designed around the 
interelectrode capacitances of the 6JS6C finals and they work
best in ALL regards using the 6JS6C, NOT 6146 finals.
I don't know why I did it,  I assumed the problem was coming from the
PA oscillating or doing strange things.  So I pulled out both of the
and the receiver birdies and all the problems cleared up.  I decided to
back both rigs up to their stock factory configuration, replaced the tube
all the capacitors and the parts back to original.  NO MORE PROBLEMS.
in the receivers, full output from the finals and everything was just
like new!

I'm telling you Stu, I think you are asking for a lot of head aches and
In my experience having worked with these rigs for some 25 years, I have
not seen a 6146 modification that I would want to own.  I highly
you rethink this as the tubes are still readily available and even a flat
of 6JS6C finals would give you less head aches then having to work
all the problems you will more then likely encounter by doing a 6146
to a perfectly good FT-101E.   Every time I see or hear about this
modification, I just cringe!!  In fact just FYI, there is a so called QRP
/ FT-101
on E-bay right now that has a 6146 in it.   Think about it, it's QRP of
sorts!  Why is it QRP, more then likely it just doesn't work right.   I
feel sorry
for the winning bidder that picks  it up too.

I'm sure you will get varied opinions on this Stu.  After all it is only
ham radio and I would not want to discourage you from the
spirit of experimentation and learning, which is all part of the hobby.
But in my experience I usually see these rigs after the fact 
being sold on the second hand market as inoperative or on my
work bench with the owner wondering why it's not working right.
I belive in fixing a rig so it works right and last a long time so it
come back,  so if the finals are still available (which they are)
then I'm convinced, IF IT WORKS NOW  -DON'T FIX IT !!
If you want an FT-101 that has a pair of 6146 finals
then find yourself an FT-101ZD.  I think you will be a far happier camper
in the long run.

Best Regards for now and if you decide to do it anyway.
GOOD LUCK my friend.
Carol L. Maher

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