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Re: QMX kit arrived w/damaged L501, is it a problem?
Maybe it is regional... My QMX+ kit arrived today in PERFECT condition. No damage to the outside packaging. The 1st thing I checked was L501: AOK inside an anti-static bag, inside a paper envelope, inside a cardboard box, and the FED-X plastic envelope.? So.... to this southeastern corner of the USA, a happy result.? FED=X people here are careful.?
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72 de N4REE, Bob Easton - QRP CW forever |
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Re: QMX Rev 4 Schematics
Andy,
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With that current draw, there is very likely something shorting or not connected properly on your board - this is much more common than a component failure, especially capacitors which rarely fail (but could have poor soldering).
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Since you feel the 5.6V zener getting hot, it means it is sinking power, which it does to protect the output of the 5V supply from going too high in voltage.? This can happen for a few reasons: 1) the 12V bus is shorting somewhere to the 5V bus; 2) there is a short somewhere on the 5V bus; 3) the ADC_5V signal is not getting to the processor properly; 4) some other less likely smps or component fault.? Since you measured that VCC is following the 12V rail, the first of these is likely your problem.
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It would be wise to reduce the current limit of your power supply to 250mA while you finish troubleshooting, as it is less likely to damage something.
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So I would check again very carefully for solder whiskers across the board, and for other possible shorts.? If you remove your 5V SMPS and measure the resistance between the 5V pin and Gnd on the main board, you should see a resistance of a few K-ohms - if it is less, you need to check for shorts on the main board, otherwise the problem may be on the SMPS or the interconnect.? There is a good entry on the wiki of this group about independently testing the SMPS boards for issues: /g/QRPLabs/wiki/37128
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Your 3.3V supply and processor are likely working ok, otherwise the 5V wouldn't even be on.
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Regarding the SMPS from your other units:? they are fundamentally the same, but there have been a few updates: 1) relocations of components, to avoid soldering and assembly issues; 2) sometime after original smps, another resistor R115 was added to reduce the voltage on the LIN_REG_EN pin - this is not critical, and is not in the QMX+ design; 2) the 5.6V zener was changed from a small 0.5W part to a much larger 5W part.? So if your other SMPS do not have the larger zener, I would not use them on this unit until you make sure the fault is not in the connections or on the main board, since with the fault still present, you may burn out the smaller zener.
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And regarding the QMX schematics, the rev 3 schematics are identical to the rev 4 implementation with one minor exception, which is the wiring of pin 4 on the PTT output connector (which rev 4 moves to pin 2 where it should be).? So you can use them with confidence in debugging the rev 4 QMX.
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Stan KC7XE |
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Re: QCX buzzing sound on key down
John,
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Just checking: when you say that it is a good battery are you measuring the voltage under key down/transmit conditions or just during RX.? When a battery is low, it may measure 12 volts during RX but when the transmitter is keyed the voltage would drop to where it made noises.? ?Just hate to see you tear into the rig if it is something more basic.
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Brien - KE7WB |
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Re: QMX new build showed up as USB but unresponsive after firmware transfer
开云体育Just to clarify, also re-arranged on the top of the board. But no documentation exists for these changes.
? ----- Original Message -----
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CW Practice / Rag Chew
开云体育On 2/24/25 I had a CW practice / rag chew session on 20 meters. I worked five stations:?
Conditions were good. SSN = 186, SFI = 210, A = 7, K = 3. I will be doing another CW on the air practice session Tuesday?25?February. Anyone is welcome. This practice is intended for operators who are new to CW or they need some practice. IT DOES NOT MATTER HOW POOR YOUR CW IS. Mistakes are OK. Poor fists are OK. Slow speed is OK. Really slow speed is OK. This practice is meant for you to improve your CW. I will do my best to adjust to your skill level. Operate at any power level. If several stations show up, I will operate as a round-table control station. I will do it as a round-table so everyone gets a chance to transmit. Please listen to my directions. Details: Date - Tuesday 25 February Time - 9:00 AM Eastern Time / 14:00 UTC Band - 20 Meters How to find me - I will find a clear frequency and call CQ. Go to the Reverse Beacon Network and search for my call sign AB8DF. That will tell you what frequency I am on. Tune your station to that frequency and if you hear me give me a call. If there is a QSO in progress, please wait for a break in the action. Then send your callsign. If I hear you, I will invite you to join the QSO and start a round-table QSO. Reply to this email if you have questions. IT DOES NOT MATTER HOW POOR CW IS Ed AB8DF |
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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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N4REE - Bob
Brien - KE7WB
Daniel Conklin