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Re: For my open ticket
I thought I had the wrong pair of glasses on! ?????? On Mon, Feb 24, 2025, 11:16?AM Daniel Conklin via <danconklin2=[email protected]> wrote:
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Poor Mans ESD Safe Work Surface
Thought others might be interested in this.
Picture attached of my low-bucks ESD work surface.
Built my first one about 25 years ago and a second one recently for my winter QTH.
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Materials Needed:
24 x 24 x 1/2 inch Smooth Sanded Birch Plywood --> (Lowes - about $18.18 today)
1/2 x 3/4 x 1/6 inch aluminum angle strip - 4 feet --> (Home Depot - about $9.27 today)
#8 Flat Head Sheetmetal Screws -- I like stainless steel
ESD Wrist Strap (got to be lots avail from Amazon - choose one and use it! )
Simple, you wire-on replacement AC plug with screw terminals inside. remove the Hot and Neutral prongs
1M ohm resistor.
1/2 round bead edging on the bottom front edge and/or top edge for appearances if you'd like.?
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Misc:
wire, ring connectors, alligator clip for wrist strap if it doesn't have one already,?
Heavy Duty Extra Wide Aluminum Foil, Scotch Tape,?
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The aluminum angle is screwed down on the top two sides of the Birch board.
Four evenly spaced screws per side. LIGHTLY countersink the holes for the flat head screws so they fit more flush.
That aluminum strip is only 1/6th inch thick.?
The board is just enough undersized in thickness that the 1/2 inch side of the angle just covers the edge without sticking past the bottom.
The aluminum foil is taped to the top of aluminum rails with plain old Scotch Tape. Clear the tape a bit from around the top left and middle screws on the left side.
Then use a ring connector and some wire to tie in the 1M ohm resistor to 'ground'.? And leave one of the middle left screws noted above a bit above the surface of the rail, clip in the wrist strap and gently snug down the screw.
Check continuity and verify the resistance to ground at several points on the foil and from the metal dot that connects to the inside of your wrist on the ESD strap.? Get in the habit of using the strap when ever you are handling potentially (or known!) ESD sensitive components.
In addition, just in case, I've gotten into the habit of touching the foil surface with both hands after sitting down to work, just in case a BIG spark in waiting has been building up :)
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After a few work sessions, just peel and replace the foil for a fresh looking surface.
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GREG KI4NVX |
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Re: Testing for a dead QMX board
Jeff, you are a real asset to the QRP Labs community. Thanks for all you do. Mike Krieger On Sat, Feb 22, 2025 at 10:25?PM Jeffrey W Moore via <jeffreymoore=[email protected]> wrote:
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Re: QCX buzzing sound on key down
When it’s keyed the tone is produced and doesn’t transmit or stop till reboot. The paddle inputs are direct to the mcu. It will send after a reboot for a few characters and just stop responding. I am thinking that an input pin or output bit may be failing. The tests were done from a good battery. The dipole is up 30 feet out 100 feet of coax and low swr. Yes other things could be wrong but swapping the mcu eliminates a lot.
-John N4HNO |
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QMX Rev 4 Schematics
Hi all,
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I just built a Rev4 mid band QMX. I’ve encounter a strange issue, I’m hitting just below the current limit on my supply at like 470 ma (limit set to 500 ma). This isn’t my first QMX build and I’ve ensured that I didn’t short anything before power up.?
I’m looking at the schematics and I see Rev4 schematics haven’t been released. The PCB layout images are also set only Rev2 in the documentation.?
With some testing I’m seeing the 5.6V diode (circled in attached image) getting hot on the first power supply board. I’m seeing PWR_ON held high, so that means the board hasn’t tried to turn on. I’m not able to maintain the VIN, so something is pulling it down. With some probing the PWM_5V line looks to be okay. VCC seems to match the 12V rail. Looking at the Rev3 schematics I’m thinking there is a maybe a bad capacitor there.?
I haven’t swapped the PSU boards on my other QMXs because they look different and wanted to check the schematics first to see if the issue is local to the PSU board and do a little more troubleshooting before swapping between board revisions.
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The second PSU board also has a warm component, but I’m thinking that’s coming from the undervolting from the first board. I’ve been testing without this board to try and isolate the issue first.?
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Also open to other thoughts if folks have seen this issue before. |
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Re: SMD chip rework equipment
I have two of the WEP solder stations posted by Jerry.
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One for each of my QTH's.? Lots of hours of use on both.? I've built a QMX, 2 QMX+s, 2 QDXs, 3 50W amps and a handful of small support equipment kits and small proto board projects with them. Not a great assortment of tips available but they get the job done. The hot air gun works great and the temperature controls seem to work well ( and fast) for both the iron and the hot air gun.? I thought the included solder was iffy and just chucked it. The tweezers are very, very handy. Solder sucker not particularly great. Ones with flexible, replaceable silicone tips are much more useful. It appears that right now in the US they are only about $45 on Amazon.? ... End of Uncompensated Testimonial. :)? P.S. I recently needed some more solder wick. Got some ChipQuik brand from Amazon. But more expensive than the who know where it came from stuff but BOY does it work. I found that adding extra liquid flux ( as I have done for years) actually didn't help. Just lay it on the area, apply a hot tip and hold a little longer. Wicks up spectacularly well. Add a bit of fresh solder to the point in question and it often clears through-holes in one pass.? GREG KI4NVX?
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Re: SMD chip rework equipment
There's not much point in cleaning out the solder from most through hole parts.
I often just clip the old part out with diagonal cutters, heat and pull out the old wire leads
from the board, double over the wire of the new part where it will touch the board so there's
more surface area, then solder the new part to the pad with a glob of solder.?
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The exception is any part that needs a good strong physical connection to the board or
needs exact placement.? For the QMX, that would be the off board connectors.?
For those I'd try to clean out the old solder from the hole.? Solder braid and flux works,
and maybe run a toothpick into the hole when the solder is molten.?
I've never had need for a fancy solder sucking rework station when working at home.
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Some of the cheap tools available now work pretty well.
Here's a dozen tweezers of various types for the price of one brand name tweezers:
These diagonal cutters work well: ?
This soldering station plus hot air gun looks promising if you really want to spend $45.
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I've used the first two items, but have no experience with the soldering station.
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Jerry, KE7ER |
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Re: SMD chip rework equipment
If you follow the link, you'll find them on sale for $3.99. Lesson learned, test posting a hyperlink before posting to the group! 73 de George N8AHT
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Re: QCX buzzing sound on key down
开云体育Before you start ripping apart your rig and blaming the microcontroller, are you absolutely sure this is not AC ripple in the power supply??? ?Receive puts no significant load on a supply, but transmit does, and if the main filter cap in the supply is not up to the task then ripple will get past the challenged voltage regulator. A digital meter won’t show the ripple on the power supply, but an oscilloscope would.Another idea is that RF is getting back into the rig and disturbing circuits such that buzz is produced. That’s where my money is. I used to teach system repair. New students too often blamed the big chips they didn’t understand yet, instead of considering the many other simple possibilities. Another useless approach too often employed was the random measurement of voltage around the circuit, presumably in the hope that something might appear to show them where the fault lay. Often the probe would slip, there would be sparks, and now the circuit really did have a major fault. Measurements are to confirm or falsify a suspicion based upon an understanding of how a circuit might fail and produce the observed symptoms. It requires logic. In this case you need to think “How does this circuit function and what would cause a buzz in this circuit during transmit?” ?The microcontroller is way down the list of suspects. Dave On Feb 23, 2025, at 21:24, Tech Guy via groups.io <tech48055@...> wrote:
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Re: SMD chip rework equipment
You might want to try this instead.? Anti static is always a good feature for handling these chips.? Not sure what shipping is, but price looks competitive too.? I've also found some eyebrow pluckers that are super fine too!
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73s de George N8AHT https://www.ifixit.com/products/tweezers?variant=39371667406951&pk_campaign={US|Shopping|MiscTools}&pk_source=google&pk_medium=cpc&pk_kwd=&gad_source=1&gclid=CjwKCAiAzvC9BhADEiwAEhtlNyDb1w_R5dvjWRCmtKsDGGwsuWA28iuXm_j5y01SV01iTJ8Ts3L5tBoC7BEQAvD_BwE
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Re: QMX new build showed up as USB but unresponsive after firmware transfer
Florin,
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? Looking over this thread you noted that your VDD - GRN resistance reading is 55 Ohms on the main board (should have a reading of plus 2k Ohms).? ?This would concern me and would lead me to believe that your 3.3v rail is drawing too much current.? ?Possible not fully reaching 3.3v when commanded by your MCU after initial power up sequence.? ?I believe that is why you can only keep your QMX powered on by holding down the power button.
? I strongly suggest that you stop the practice of holding in on the power button as this could be damaging a component(s) that is the cause of the low Ohm reading.? If could be a shorted cause by a solder shorted bridge.? ?I am glad to read that the QMX is responding the way you described as this mean that that the MCU is still working (If MCU burn out BIG NO GOOD, but your is still working).
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?My suggesting:
1. DO NOT APPLY any power to your QMX anymore.
2. Continue Problem Solving the low OHM reading on the main boards VDD - GND issue.
3. Looking for possible bad solder bridges.?
4. Damage components on the 3.3v rail that maybe shorting the 3.3v rail to ground.? (Still check by using you DDM on Ohms setting.? ?No Power applied to your QMX- No Battery or Power Bank Plugged to it).
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Your QMX has an issue on the 3.3V rail per your posting of you what you had when you posted your VCC-GND and VDD-GND results.
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? To keep from any further damage to you QMX- DO NOT APPLY POWER TO YOUR QMX (Until you resolve the LOW OHM READING on your VDD-GND).? ?Sorry I just want to make that very clear, so you don't lose your QMX due to burning out a part that is not easily obtainable (The MCU with Hans' encrypted Boot Loader.? They are not sold currently as a replacement part).? (@ Hans,? I understand why, to protect your intellectual property).
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?You can search this forum and find how to safely apply power to the QMX to limit Voltage and Current so to not to damage components to help track down the culprit with this type of issue.? But from what I read it sounds like you may not have a power supply with these capabilities.? ?Forgive me if I assume wrong.
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? Hope this helps and good luck with your build.
73 KQ4DTX
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Daniel Conklin
Richard Dyer
Donald S Brant Jr
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