[Qcwa] Brag fun

[J Craswell]

Jim had some great comments on D.I.Y. and I wanted to put in my two cents
worth.

>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
How True.  When I worked at CPT Corp and started repair jobs by visual exams
and sniffing for burnt stuff I got some VERY odd looks.  The grads of the
local Vo-Tech had never seen such a thing but this common sense approach
repaired more things faster than the other schemes they had been using.
After a while most started to dabble in this approach.

Jim talked about using a signal generator with calibrated output.  And with
the world of surplus I think that is a great way to do it.  When I was
fiddling with my AD DDS generator I was wondering what I could do to adjust
the output for just crude alignment etc.  Roger (WA0VLL) said, "What is
wrong with using a Pot?"  I had all sorts of schemes using switches and so
on and never thought of the simple approach.  If your tuning a front end or
aligning an IF why not?  If you have a scope you can look at the output
level.

>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.

Jim is right on the nose here.  I also have a $10 set of those radio shack
jewelers screwdrivers, diddle sticks (*NEVER USE ALLEN WRENCHES TO ADJUST
INDUCTORS!) Forceps, side cutters and pliers.

>  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.
*Note Correct me if I'm wrong but the main problem with static destruction
of small parts was due to a single family of logic that had no clamping
diodes (Or other protection schemes) in the inputs.  Looking at the parts
sideways made them blow.  That problem and those parts are history.  I've
never given a seconds thought to static mats, gloves, cloths, sprays etc.
And I've never had a problem either!  One of the geniuses at one of the
Companies I worked at told me that this business of saving parts from static
damage was a pretty amazing scam and that the folks selling this stuff were
really laughing themselves crazy.  For how could they fail when the problem
went away long ago?

Jim made a good comment about getting parts.  For Amateur Stuff that is
current you can order it direct.  Some of the exotic stuff like CPUs and so
forth are impossible to get elsewhere.   Many parts are simple commercial
parts with vague part numbers and finding out what they REALLY are is the
only problem.  The internet while mostly only good for SPAM and internet
Porn does have some good resources for iding part numbers and who makes
them.  Then you have to be willing to go beyond Digikey.  I can't tell you
how many places I talk to think that if Digikey and Mouser don't have it we
can't buy it.  Check out the 1000s of other places that sell parts.  Most of
these places want fairly large orders so instead of buying 1 resistor (ala
Radio shack) for $.49 you will need to buy a reel of 5000 for $15.00  The
one and two-see parts can often be gotten as samples.  If you get into that
it's best to be honest.  Tell them your a mom and dad repair shop and don't
order tons of material.  If you pretend to be IBM and never order they will
be POed when they find out your Joe Schmo in his basement.  Offer to take
them out to lunch.  Most customers do anything to avoid salesmen!

>The scope is a very nice addition
>to any bench, but not necessary in all applications.

True but they prices are so good and a scope while overkill for many things
can do SO much!

>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.

On the Lightning blasted Icom 2 Meter set I found that everything connected
to the outside (Except Xmit) was burnt or exploded.  The Audio chip was just
pins going up to a black spot on the case.  The front end bandpass filter (I
think) had superheated and all coils had vaporized the enamel and turned
into toaster elements.  The DTMF Microphone was melted.  I replaced the FET
in the receiver front-end and got better reading on the S meter.  Then I
removed the remains of the coils one at a time and estimated the gauge of
the wire and rewound coils on old drill bits to keep the diameters the same.
This made the receive peek up.  Then I tacked in a cable to an external
audio amp and found the receiver was working ok.   *I later realigned the
set but this didn't change it much.  The Microphone was a mess so I took out
the DTMF board and tossed it.  Last I looked around for a replacement Audio
Hybrid and got the word that the cost of it was pretty crazy.  I took an
LM386 (If I remember right) IC and made a little Audio amp on Vector board
and glued it inside the case of the radio neat the smoked remains of the
original amp.  Transmit worked fine which had me confused but happy.  XYL
has it in her car.  50 Watts on 2 which is very mighty fine!

The FT-100 I bought (Broken) had almost no receive.  It could just pick up
the 50,000 Watt WCCO station on the broadcast band.  I downloaded some
sheets from the service manual that some guys had posted on the internet and
did a complete alignment.  *Note I had to file down some diddlesticks to do
this.  Each stage peaked but the results were beyond bad.  So I poked around
for a while and in the end sent a quick email to Yaesu Tech support and they
thought about it for a day and replied that perhaps the -9 or +9 supplies to
the front end op amps was dead.  IT WAS!  -9 was zilch.  I found the part
and did some searching with the cryptic part numbers using part miner and
got the data sheet that made sense.  A DC:DC converter.  +13.5 in and - 9
out but mine was doing nothing.  I removed the output inductor (Through Hole
Part) and plugged my DVM on the output of the chip.  Nothing so I figured it
was bad.  I order one from Yaesu (3 or 4 bucks) and snipped the SMT legs on
one side of the part and heated all the rest of the other side at once (With
my big soldering iron tip) and plucked it off the PCB.  Then I removed the
remains of the otherside and soldered down the new part.   This did nothing!
I got up close with my magnifier and saw the SMT resistors appeared to have
cracks.  These were two very low resistance parts in parallel (To lower it
further)  I removed them and replaced this with two 1/4 watt resistors.
Power on and it worked!  I replaced the inductor and everything worked!  I
did a realignment but nothing could be improved *I did buy the service
manual from Yaesu.  Very well done, easy to read.  Not much on
troubleshooting but as long as these guys at the repair shop are so helpful
I'm happy!

>Sure wish I had a sweep generator though.

I ask from total ignorance what sorts of things would we be able to do with
a sweep generator?  Looking at Xtal Filters designs? or ?

73 de Jay W0VNE