[Qcwa] Bragging Rights (A good thing!?)
Robert Harvey
[email protected]
Wed, 10 Jul 2002 09:28:16 +0200
Jim and the group:
To answer you, I think SMT is never going to be a
favorite of mine; my eyes are fine, but I drink far too much coffee to
keep the hands steady enough early in the day, and SMT is really not a
late in the day project!
I agree on the dental tools; I have a set myself, and
they really are useful. The ones that are single-sided I dip in plastic
coating to insulate. Since they are all metal, they ain't the safest
tools around live circuits...
Why two Hemostats, or am I missing something?
Here's another useful item: RS (and I'm sure other
stores) sell a little amplified speaker which uses a 9-volt battery and
has min-phono inputs. I've had one of those as a signal probe for a
long time. Make a lead, attach a reasonable value Cap to the end, and
you can read audio from the detectors/mixers beyond to your front end.
It's helped me quite a bit, particularly when I wanted to receive FM
subcarrier audio, and needed a place my receiver could pick up the audio
prior to filtering.
I will agree with you on the 259B, and would comment
that if you are a VHF/uWave person, the more accurate your test
instruments, the better, so my last post was somewhat wrong.
Some of the most vexing problems I've had to counter
were those caused by human capacitance. I have too often made a
measurement, continued on, and only after a while realized that my hand
capacitance had made a joke of my measurements previous. I have a real
problem realizing when I am affecting the circuit!
73, Bob, K2PI / ON9CPI
Brussels
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of WILHITE, JIM
Sent: Monday, July 08, 2002 11:48 PM
To: QCWAlist
Subject: Re: [Qcwa] Bragging Rights (A good thing!?)
Bob and Jay,
One of the things taught in technical electronics school is logic. It
has that name for a reason. If anyone will approach repair with common
sense and logic, much can be done. I have often heard teachers in lab
state to the students: "If you break it, we will fix it" (meaning the
test equipment).
Decidedly SMT requires a much steadier hand than I have today, so I
don't approach it unless it won't be repaired at a shop. I have small
hands but the way I use them, you would think they are hams. For that
reason I use the old and classic gear and work on it quite regularly.
But as for test equipment you guys are right on. I have a URM 25 signal
generator which has calibrated output (25 bucks at a hamfest and I had
to work on it to get it going). The calibrated output is only necessary
if you desire lab results or measurements when aligning. It has two
outputs, high level which I hook to my counter and the calibrated output
which goes to the receiver under test. Sure it wanders and I have to
keep my hand on the frequency knob, but so what. The approach Jay
mentioned of building a simple one does not have the wandering problem
and is cheap and easy to do. Just keep the input below the AGC/AVC
level and you can't go wrong assuming you are touching up a circuit that
has been aligned before. Add to that an audio oscillator which are
cheap and plentiful. Hook your generator to the counter, set it, then
move the output to the receiver you want to test.
With the soldering station I would add some dental tools (picks, one or
two), two pair of hemostats, tweezers, a good collection of
screwdrivers, small wrenches (a pouch of ignition wrenches can be bought
from Sears), alignment tools and good cutters, needle nose pliers, allen
wrenches, and nutdrivers. Pick up phillips and flat blade screwdrivers
that hold the screw for upside down vertical or horizontal insertion.
I am not sure about using solder suckers on SMT since some of the
diodes, logic chips, FETs and other components are very sensitive to
static electricity. Solder suckers can cause static electricity. In
its place I would use the wick, and be sure it is a very good brand (not
Radio Shack). Also remember to work on a surface using techniques that
reduce static electricity, especially around SMT, CMOS and the like.
Sometimes the most challenging situation is finding the parts. Many
parts in modern radios are not available in the common market and once
the model is discontinued the parts production does as well, so you may
have to be resourceful as stated.
Have one very good multimeter like a Fluke to calibrate others you may
use against it as a standard, (less than $75 brand new with .25%
accuracy). I use a Simpson 260 and an RCA Senior Voltohmyst most of the
time. Some circuits utilize very small voltage changes and they are
difficult to measure with an analog. The scope is a very nice addition
to any bench, but not necessary in all applications. Not that I haven't
had to use one to find a particular problem from time to time, but not
much of the time. I have a dual channel 50 Mcy. version, brand is not
important and around most circuits calibration is not either.
I have the MFJ 259B and it is a very nice piece of equipment for
ballpark measurements. It does a lot but, used in tuned circuits, it
will not give sign of X. For all it will do within its limitations, I
do recommend it especially for the counter and its ability to measure
coax loss, faults and length.
Depending on frequency, accuracy can be an issue. And everything I have
falls into the accuracy category that amateur radio requires. Most of
it will not fit the bill in commercial service, but kind of accuracy is
not commonly required in amateur radio. So I go with your assertion.
The counter should be checked for accuracy if used to set transmit freq.
and should be checked regularly. The variable temp. soldering station is
a must. Keep that tip clean for maximum heat transfer and wipe it off
every time you use it.
You guys are surely on the right track here and it would be interesting
to read some of the problems you have encountered. In my case the most
challenging problems can be disassembly and reassembly after repair so
it is best to have the manual close by.
Altogether I have spent less than 350 dollars for my equipment over a
period of about 10 years including the 259B. Watch those hamfests, test
equipment is all around and mostly cheap. Sure wish I had a sweep
generator though. Good posts.
73 Jim
de W5JPW
Quite impressive, and you've obviously thought this out. You sound like
an accomplished tinkerer (and I use that term in only the most
complimentary sense)! I have in the past been able to repair all my own
gear, and I've worked on Surface Mount devices with little more than a
low-wattage iron, a pair of tweezers and not a little luck. It is, as
you say, very satisfying.
Unfortunately, for me, many times I've found things that I absolutely
cannot match with the junk box, or custom ROMS, or some proprietary LCD
display driver IC that I can't do much with. I can recall spending a
good 16 hours working out an old burnt out display and soldering in all
55 pins of the new, and feeling I accomplished something at the end. I
still hated every minute of it till the end, and begrudged the time it
took.
It would be interesting to hear, from the sagacious among us, just what
they feel comprises a minimum "bench" setup. You'd already mentioned a
variable Soldering Station, VTVM (or decent Fluke type DMM) scope and
signal generator, which I have, but I'd add a Freq Counter, dip meter
(or equivalent) and a variable DC power supply. You know what I really
like? Those MFJ antenna Analyzers. Not just for the stated use, but
because they incorporate a Freq Counter and Dip meter as part of the
package. For less than 250 bucks, that's quite a lot.
I'd also think we could hear some groups on the accuracy needed in those
test instruments. I've worked with people who scorn anything without
accuracy approaching PPM levels, and with others who say whatever you
have, estimate when needed (I tend to lean towards the latter).
73, Bob, K2PI / ON9CPI
Brussels
-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of J Craswell
Sent: Monday, July 08, 2002 6:14 PM
To: [email protected]
Subject: [Qcwa] Bragging Rights (A good thing!?)
I suppose what I am trying to say and what I hope people will think
twice about is that my bench equipment. i.e. the gear needed to do this
is not that extensive. If we accept that a typical Short Wave Radio
costs a grand then the tools to work on it or build new stuff ought to
be less than that. I'm easily way under that. And I think my modest
set up is just that. A modest
bench. An adjustable temp iron is really not that expensive. Can we
stick
to our 100 watt solder irons? No, of course not. The cost of solder is
low a solder sucker (ditto) tweezers (ditto) Now the test equipment can
be anything you like to use. I've got one of those DVMs (From Radio
Shaft) and I have an old beat up signal generator from HP but a guy
could build his own (As I did) with an Analogue Devices DDS chip for
next to nothing. BTW the HP was a couple hundred bucks because someone
dropped it on the face and
bent the handles. The use of a scope is I think not so exotic as it
might
have been in the 50s. What is important is that the price of a good
used scope is pretty amazing. I bought a 350MHz Tektronix scope for a
couple hundred bucks and love being able to "see" what's going on. Being
alive today and be able to own such super science equipment for next to
nothing is a big plus! The good old days? 500 KHz scopes and 6V6s? No
thanks!
I think being able to fix your own gear is a plus. Is it for everyone?
Well no - but I don't believe it ever was. What I think we should
promote
is that it "ought" to be for more folks. (In my opinion) I don't think
we
should make general statements that no one builds their own gear or that
no one can fix this new stuff like the good old days. Heck I remember
thinking the new parts like Transistors and ICs were too Hard and how
could anyone work on that junk? Nuvistors were good! 723 Regulators
were bad. <grin> The problem as I see it is that new hams not knowing
any better will nod their heads and turn into Appliance operators when
this is the last thing we need. If you step back and look at it this
era we live in is actually pretty nice with the mentality that anything
broke is Landfill. I can't tell you how many items I've gotten for
little to nothing and am using everyday. I've got a Lightning blasted
FT-847 that works like a charm. A FT-100 that had a bad -9 volt supply
also working like a charm. It's all powered by ASTRON supplies that
were "burned up" My XYLs radio is another
lightning special. That one was really toasted but a new audio circuit
(The real one cost too much so I glued in an Audio chip I had in the
junk
box) and some parts in the front end and some new coils put it back on
the air in good fashion. Heck I may never buy anything new again as
long as people break stuff and want to toss it! <grin> My cost on a
most of this was the gas to drive over and pick it up and the
replacement parts. Did I spend a lot of time on it? Some I did others
not much. If I was charging $75 an hour as some techs do I think I
would still be way ahead. But I don't charge $75 to fix my own stuff
<grin> And it's fun and gives you a little bragging rights which I hope
my fellow QCWA members will do more of. Bragging about being able to
copy 20+ wpm is good. Ditto designing your own radio etc. Isn't that
one of the goals of the part 97 regs? Increased operator skill and
technical ability?
73 my friend! de Jay W0VNE
p.s. KA0KLV reports my repair job on the little Icom is still working.
(Got my fingers crossed) He is buying lunch for sure!
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