Gang,
Due to some email back and forth between a couple of individuals in
debugging a TenTec 1340, I have decided to bite the bullet and post
the following measurements for the aid of anyone having difficulties.
Please excuse the bandwidth. These people are having trouble getting
through the phone lines to TenTec.
One of things that is great about this group is the number of people
that help others. A lot of this is going on behind the scenes and
involves personal email, phone calls, faxes, snail mail, and all kinds
of technologies known to mankind. Someone reminded me the other day
what is best about this group on 'elmering', i.e. the instructing and
helping of anyone to learn more about any given topic. And that
something about this group is not only the elmering but the fact that
we are doing this remotely. The individual with the problem(s) still
is the one doing the work.
Typically what happens in debugging is that the knowledgeable person
comes over or the other way round and all the individuals involved get
out the equipment and start right in. Before you know it the person
with the problem is on the sidelines observing. That is not the way
it should be and probably most often it is not, but even one time is
too many.
Also, doing things remotely the person working on the problem can take
his or her time and learn at their own pace. They just have to be
careful, patient, and be sure to ask questions when the need arises.
Now with digital cameras we can even set up a scenario and photograph
it and put it on the net in a matter of minutes and show all the gory
details. Ham radio is not the only endeavor that is gaining in this area
on the Internet.
Anyways, here is the data as best I can give it. I have first
started with a reference voltage from the power supply. Adjust
appropriately and remember boys and girls your mileage may vary,
i.e. your voltages don't have to that exact. Ballpark figures will
generally work. If you think your voltage is too far off, let us know.
OK, be very very careful measuring these things. One lead from your
probe shorting a 12V line to another part or another PC board trace
will and can do considerable damage to the rig. I hate it when that
happens. And there aren't too many of us in this group that have not
done this if we have played around with a number of radios and such.
Been there. Done that. PC board traces make nice fuses. The most
expensive part in the whole rig makes a good fuse. Back in the tube
days we were working with hundreds of volts and lots of power and it
was more dangerous to humans. One of the reasons why I have never
owned a large amplifier except for when my dad died and left me a
Collins 30L1. I immediately sold it.
I am using a CircuitMate DM73 small digital multimeter. I like it
'cuz it has a fine point and can fit in small quarters where I need
to make measurements. So, whatever meter you are using use a fine
point to make the measurements. A piece of insulation over the tip
except for the very end will save you a lot of grief. (A Hint and
Kink for Paul Harden). We'll be doing the following from the top of
the board as my rig is assembled, working, tuned, and just fine thank
you and the Chuck Adams DFW rule is in effect. If I zap this thing
while I'm doing this you will hear about it. :-) Even if I don't
have to tell you.
DANGER: Be careful on the leads to parts. The lead may be at 12V
or so. There is a ground plane nearby. Stay the heck away from it.
It is not insulated with a solder mask. Keep your multimeter lead
away from cases of IF transformers as they are at ground potential.
I am not trying to talk down to anyone with these instructions,
above and below. It is best to start at ground zero so that I
don't lose anyone.
----------------Measurements to follow---------------------------
Power Plug at + terminal = 12.79V
Using the X-Ray View foldout, reference section page 29, with
radio front towards you as shown, lets start in the upper right
hand corner. Oh, turn the radio on and the P/S. :-) ;-)
You won't be measuring anything without power. I did this. :-)
Good batteries in the meter will go a long ways too.
Q10 left leg = 12.79V
R54 left end = 12.79V
R51 left end = 12.79V
JMP3 both ends = 12.79V
JMP1 both ends = 12.79V
R12 left end = 12.79V
R33 left end = 12.79V
R33 right end = 12.32V (careful here, don't touch the crystal)
L15 any wire = 12.79V (there are three points on the top)
R61 upper left = 12.79V (this is the variable R)
R7 upper lead = 12.79V
Pin 8 of U2 = 12.79V
Pin 8 of U3 = 7.09V (this is a drop due to R12 and is good)
(TenTec is running the NE612 at 7V)
Pin 6 of U1 = 12.79V (be careful here)
OK, figured out where I was going with this? This pretty much
covers the active components in the receiver. If the voltage
disappears along this list then you have a bad solder joint or
you have a shorted land or an open land (PC trace).
OK, it's about 0640UTC (Z, GMT) Wednesday. You have 8 hours to
ask me to measure another point. After that it's 10 days before
I see this puppy again. :-(
Good luck and may the Force be with you.
Beam me up Scottie.
dit dit
SIG
Chuck Adams K5FO adams@sgi.com DXCC=9
http://reality.sgi.com/employees/adams_dallas/
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