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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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Fw: [QRPLabs] QMX new build showed up as USB but unresponsive after firmware transfer
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Re: QMX new build showed up as USB but unresponsive after firmware transfer
开云体育I cant find any reference to the SMPS 5.6V PCB and it's different configurations, I see in the latter type boards C104 has been removed. However all the Assembly manuals show the original board configuration, including listing C104.
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Having a few problems with the boards I have created a 5.6v PCB searchable document attached. Hope this helps let me know if there are any mistakes please.
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73
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Ian G4GIR
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Re: QCX 50W PA multibanding?
#50wpa
?As for the interactions, I would not expect that "just appending" a lower-frequency section would "just work" but it sort of does. I.e. leaving the original LPF as-is and just plugging in an extra Pi-network designed for the lower frequency (input capacitance of the "plugin" adds to the output capacitance of the "original") does not destroy the general frequency performance (at least not too much, see below).
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My simulation of an extra LPF stage for 3.6 MHz appended to a 7 MHz LPF shows that it works fine if it is designed as elliptic, i.e. with parallel resonant circuit for 7.2 MHz in signal path. However, if I omit the capacitor from the parallel resonant circuit, the combination sort of works as LPF for 3.6 MHz (it goes through) but 7.2 MHz suppression is not great (less than or around 20 dB) and there is a peak (very low suppression, less than 10 dB) around the critical frequency of the original LPF (which seems to be at around 9.0 - 9.2 MHz, at least theoretically, based on available data).
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As soon as I get some time and at least two BNC connectors I will test it :) Presumably, for 5.3 MHz with elliptic filter tuned to suppress 10.6 MHz it should be more or less the same story.
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I don't have a blog, so I have to think where to post the simulation images and how.
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73 Jindra
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On Mon, Feb 24, 2025 at 12:24 AM, ok4rm wrote:
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Re: QMX new build showed up as USB but unresponsive after firmware transfer
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Ludwig, got it that's good to know. I was already set on doing some things better from the previous build, so in the end it worked out but in case I'll ever need just the power supply boards I'll make sure to get those. Again, thanks for all the support!
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Those are some very good points, Don. The build has definitely sparked more interest in debugging hardware and relearning skills I haven't used in more than a decade at this point. I'll be applying your suggestions in the near future for sure, thanks for sharing. |
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Re: Using WSJT-X 27.7.0-rc8 "FYI"
The full release of WSJT-X 2.7.0 is now available, and is very similar to -rc8.
https://sourceforge.net/projects/wsjt/files/
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WSJT-X WILL work fine with the newly added radio selection "QRPLabs QMX" (as shown in the previous post) - but you have to upgrade hamlib to the current version 4.6.2, otherwise it will crash - the QMX wasn't properly in hamlib v4.6.1.
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Stan KC7XE |
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Re: QMX SSB on 4m?
Hello Tony ?
I see no reason why not, though I have not tested beyond 6m.? Note also that the maximum update rate of the '5351 clock generator, when using 1MHz I2C bus, is around 16,000 times per second. This is not dependent on the operating frequency of the '5351. So there is no reason why it would be different on 70 MHz. And since 16,000 updates is plenty more than required for SSB modulation, it all should work. 73 Hans G0UPL |
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Re: SMD chip rework equipment
You just need resonable tools.?
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I have been using Weller, my neighbor uses? Hakko branded.
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The air gun and nozzles to warm the board so a pair of mechanical tweezers can pick off the SMD chip.
For thu hole, I use warm the area with the air gun and with the 200W iron and solder wick remove the majority of solder.
The use the Hakko Desolder gun to clean it up more.?
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The Soldering Tweezers are the best to desolder SMD chips. Occasionally I will solder with them.
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For the most part I use the 70W iron and solder wick, Chipquick?
Second is the air gun,?
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Listed below is a SMD practice kit. Better to learn on a practice kit than to overheat a kit board or an actual radio chassis.?
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Jerry's advise is good. Youtube is a great refressher? on technique.
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I use :
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A REALLY GOOD LIGHTED MAGNIFIER.? I have a couple. one of my favorites is one with a extra high power lense that is in one spot of the?
overall magnifier lense. If you can't see it clearly, you can't fix it or build it better.
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Flux solder, solder paste and liquid flux, 90% isopropyl alcohol and lint free rags are the consumables.??
Compressed air is a plus.?
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An basic temerature controlled air gun with a variety of tips to focus the hot air stream.
Air Gun? - https://www.amazon.com/dp/B0752Z4165
Nozzles - https://www.amazon.com/gp/product/B07G352P13
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Weller 200W Temperature Controlled Iron with an assortment of large tips, Chisel or round nose
?Iron -
Tips -
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Weller Soldering Tweezers RTW3? ?T0054465399N
https://www.amazon.com/dp/B06XCMN8W2
These heated soldering tips have flat paddles for tips and are great to grip SMD chips with and solder/desolder them
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Weller Temperature controlled 70W Iron
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Weller Assorted Tips for 70W iron
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Hakko Desoldering gun
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SMD soldering practice kit
https://www.amazon.com/gp/product/B08KDLR6P6 |
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Re: SMD chip rework equipment
I have had a hot air rework station for 20 years and couldn't live without it. Mine is a very old one with analog controls. I see many digital ones on amazon in the $35 price range which is a lot less than I paid for mine years ago. Don't know about the quality?
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For a heat table, I use an electric griddle I picked up at a thrift store. It does help the hot air a lot to have a heated board especially on boards with lead free solder. I have even assembled whole boards with it using a solder paste syringe, placing all the components, then ramping up the heat on the griddle until the solder melts.
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I would avoid the Harbor Freight/hardware store 1500 watt heat guns as they tend to blow multiple components off the board. However, I have used them in the past to harvest all the components off of old boards. |
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Re: QCX buzzing sound on key down
Thanks for the tip but I think the microcontroller is damaged. I guess I will order one. Very erratic. Voltage is ok. When booted it emits a tone constantly when keyed. Rebooting is the only way to stop it. Then it may work. It ?stops responding to the paddle input after a few characters. I am going to look a little more. I think I may have a spare microcontroller. It would be any easy test to swap it.
73s John N4HNO |
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Re: SMD chip rework equipment
Many people here have spent a fortune on rework tools.
That is not necessarily warranted when working on some $100 QRP kit.
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These boards go through an auto assembly house using no-lead solder.
That makes them very hard to work on, as that solder doesn't melt till it gets extremely hot.
Easiest way to get a part off the board is to use some low temp solder alloy such as chipquik,
there are cheaper kinds of this stuff to consider if you use a lot of it.
Melt some of that into the nasty lead free high temp solder the boards come with.
Then you can pick the part up using a hot air gun.? A cheap embossing gun might work,
though one of the $20 1500W heat gun (such as from Harbor Freight) would also work
and might be useful for larger jobs.? I've never had a heat table.
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Be sure to thoroughly clean the low temp solder alloy off with solder braid and flux.
You don't want parts falling off the board on a hot summer's day.
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I then use isopropyl alcohol to clean flux and such off the board, the less water the better
since the water takes much longer to dry off and can affect how things work.
Most of the stuff at the drugstores is 70% alcohol, but some do have 90%.
If you see the 99%, get a couple bottles.
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Here's a cheap soldering iron kit I am happy with (though I do have Hakko's and Wellers too):
Includes several tips, flux, and solder, good temperature control.
That one does not have a safety ground at the power plug,? not a bad idea to run a
ground wire from the soldering iron barrel to your workplace ground
in case there is a minor fault inside the iron.
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You might want thinner solder for some of the smaller parts, but that's a good start.
You can wet the iron with most any size of solder, then bring the tip to the pin you
wish to solder, having put a bit of flux on the pin first.
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Lots of light and good magnification is a must, need to see small defects like solder whiskers.
Here's a cheap magnifying headband that has been mentioned in the forum:
All three choices are the same except the mid-level item has a brighter light,
and the high end one also has a bag you can store everything neatly away in
if you happen to be that sort of person.
Many reviews do say that the nose rest on it could be more comfortable,
that will depend on your particular nose.
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Beyond that, basic hand tools such as tweezers, wire stripper, xacto knife, and needle nose pliers.
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Be careful about static, especially if it's freezing cold out and humidity is low.
A static mat on your work surface plus wrist strap is ideal but can be expensive.
I doubt most in the forum bother.
At least get in the habit of touching a ground point on the device first before
sticking your finger into some especially sensitive signal node.
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Jerry, KE7ER
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Re: SMD chip rework equipment
First watch several YouTube videos about diy smd replacement.? Google will give you many options.? ?There are a few different methods,? and you will want to educate yourself on them to decide how you want to do it.? Then purchase the requisite tools and supplies (they don't need to be expensive, but don't get the cheapest ones, either).? Then practice several times using discarded circuit boards (from old phones or electronics) with components comparable to what you want to work on - practice both removal and replacement.?
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Then go for it.? That's what I did, and have since successfully done several smd rework tasks.? But I have also sometimes lifted pads and had to repair them, even after some experience,? so you need to be very patient and careful.?
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Stan |
Richard Dyer
Donald S Brant Jr
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