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Excellent Repair Service, Jeff W1NC

 

When my QMX took a turn for the worse (magic smoke), I followed the suggestion many have made here. I sent it to Jeff W1NC. What a pleasant experience! In a short period of time I had my QMX back in working condition. Just as importantly his evaluation, findings and suggestions sent via multiple emails will make me a better builder. Thanks Jeff. 72 ?Peter/AA2VG
 

I concur with others that Jeff, W1NC, is providing an excellent service to this community. He provided detailed reports on his findings as the investigation into my two QMX's progressed. Diligent, thorough, knowledgeable; and all this service to others from someone that still has a "day job". Well beyond just repair, I think he truly does enjoy problem solving and helping others.

I'm looking forward to using these two QMX radios.

Great work Jeff, many thanks!

72/73 Steve W6WU
 

I wonder if Jeff, W1NC can give some general guidance on what he is finding when troubleshooting?

Is it component failures and are those parts particularly vulnerable to ESD? resistors or caps that are added? The encoder leg? display?, The transformers and bad soldering connections?

If it is soldering skills that is important for all of us to know as well. It doesn't have to be a specific example about any-one radio but maybe some things that can help the entire community?
--
Tisha Hayes, AA4HA
 

Hello all,

Thank you for the kind words. ?I truly do enjoy problem solving. ?Every rig is like a Sherlock Holmes mystery. ?It¡¯s fun finding the culprit(s).

As I have mentioned before, I find almost all problems under my stereo microscope. ?The first thing I do with any rig that cones in is clean and scrub with 99% isopropyl alcohol. ?Then I inspect under 10x stereo microscope with bright lights. ?I find most often (in this order) cold solder joints (especially on GND pads, and enameled wire joints). ?This is followed by solder splashes, misc conductive debris and solder balls. ?Cleaning these up often solves many problems. ?Next is damage caused by accidents with scope or meter probes such as bridging 5v and 12v. ? I?rarely find a bad component (that wasn¡¯t destroyed by an accident).

Sometimes though I get temporarily stumped and have to approach a problem in different ways. ?I was fixing a QMX recently that had very low output on 10 meters. ?It was about 1 watt. ? I inspected that low pass filter under a microscope. ?The toroids looked right and had continuity, the capacitors were all in their proper places. ?The diodes were good, the 47uH inductors seemed ok. ?The lpf was selected to GND by the mosfet. ?On input to the filter, I had 5 watts in. ?On output from the filter I had 1 watt out. ?Finally after lots of staring at my scope and schematics, I pulled the entire lpf circuit for 10m out and measured each component. ?There was a bad capacitor - completely open circuit. ?I think it was destroyed in a high swr event that placed a high voltage on the cap (and a few other things as well). ?Replacing that fixed it.

The bottom line for me is patience and careful logical debugging. ?Sometimes a rig takes only 2 or 3 hours to go through. ?Sometimes it takes a dozen or more hours over a few days.

i hope this helps.

73
Jeff
W1NC
 

Hello Jeff,

can I send also mine for a repair service to you from Germany?

I am struggling since weeks to find the fault

73
Harry
DK2GZ
 

QMX is on the way.
Send also a message to "sender".

73
Harry
DK2GZ
 

Jeff,

Would you be willing to share your preferred method of enamel removal from the thicker 22 gauge winding wire?

Mike?
KC2EHR
 

Not Jeff, but my solution is Knipex:??
They sell cutters for different-sized wires but the default one supplied works on everything I have tried it on.??

Knipex's stripper for vinyl-insulated wire is a superior product as well:??
I just used it for a huge wiring job and it made thousands of 100% clean strips on AWG22 to AWG12 with no bad strips nor sign of wear.? No relationship just a satisfied user.

73, Don N2VGU
 

I recently took?Don¡¯s advice and started using Knipex strippers. It is much easier and more reliable.?
--
Colin - K6JTH?
 

I'm the furthest from an expert you could want. But I have found a fine xacto blade does a beautiful job stripping the enamel. It's like peeling a potato, with shiny copper underneath.
 

Jeff,

Your debug guidance and notes on your observations are most helpful. Not just what you found but the process you followed to narrow it down to the defective area/component. A current running compilation would be excellent for educational purposes..

73 Kees K5BCQ
 

I'll second the Knipex tool. Exacto blades work, but getting all sides can be tricky, especially if there is more than one leg on a component, eg toroids.?
--
73, Dan? NM3A
 

Great input - I have one of the Knipex tools on order - should be here Friday!

Thanks to all.
 

For about 25 years I found this stripper made in Germany called the Ultimate Stripper by Buchanan made in Germany.? I used it to wire a house, a couple of shops, church fellowship hall, and countless other projects.? 12g to 20g with no adjustments at all and just hung and new light at the house 30 minutes ago and worked perfectly.? ?It does have trouble with some slick insulation, aviation wire comes to mind.? I could never find a second pair until Harbor Freight started selling a version made under to Quinn brand which I bought and works just as well.? Just looked and they don't list the Quinn model but Pittsburgh now carries it at a slightly cheaper price.? ?I can't say how much these work for FAST no brainer sripping!
??
 

Thanks to everyone who responded on the enamel wire stripping methods.

As I posted earlier, I did order one of the suggested Knipex tools.?

I finally had a reason to use it on 3 toroids and it worked GREAT!

Thanks again for this excellent suggestion.

73
Mike
 

Hi Jeff,
? ? ?If you're still doing the repairs can you give me your address so I can send you both of my QCX single band radios, they have worked but not at full specs.
Very interesting comments about stripping wire and taking off the enamel coating, I started with Western Electric back in 68 then I switched over to NY Tel. for years the only tools I used were the yellow handled long nosed flats, the ones that had the little stripping hole near the top, the originals had a space beneath the hole that was used for breaking the covering on the cotton covered wire, also the red handled wire cutters that had two notch holes, I hated them because if you didn't do it right they never cut through the cable, and of course the splicers shears, they were great for cutting the CAT cables with the string inside and they had two stripping notches on the one side, I've been retired 14 years and the callouses on the side of my index finger have finally gone away.
73 John K2IZ jsmale859@...?

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