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Based on the "fault finding" tab at , my SA ultra's input RF switch chip U22 (AS179-92LF) has failed. This chip is so tiny it seems there is not a soldering iron or tweezer small enough to replace it. It's like a microscope-dependent repair! Has anyone had success with this repair, or is it just smarter to buy a whole new SA Ultra?
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Hello.
? I don't know your soldering shills, but this definitely is on higher level.
Forget soldering irons in this case. There are super-fine T12 soldering irons, but the size is still very small.
Such parts are usually replaced by use of a hot-air reflow workstation, fine tweezers and a huge magnifying glass or microscope (for looking from bigger distance of 20cm or more).?? If you don't have that equipment, skills and a very steady hand, don't even try it.
You can possibly contact a repair center for smartphones or laptops, if they would do an exception and replace the part, but I guess this will cost more than a new tinySA. And another thought:? Is it sure that _only_ this part is the problem and everything else is 100% ok? Otherwise you burnt money and still have a not working device.
I talk from my own experience, I am not bad in reflow soldering, but I wouldn't touch that.
Am Dienstag, 1. April 2025, 09:11:55 CEST schrieben Sie:
> Based on the "fault finding" tab at tinysa.org (
> https://l.facebook.com/l.php?u=http%3A%2F%2Ftinysa.org%2F%3Ffbclid%3DIwZXh0
> bgNhZW0CMTAAAR2cSIhlkkxbkDzVcVvtqIq8v4xw9TAitngOiNPESHlhJhwvBopXUijC2xI_aem_
> auyC7fts-GLRVFjrACZsBQ&h=AT0MOG0yHNy_ltOKHUiQHDjJqBmA7dxZnSbs0lHlG1mgZK0GV-Q
> CSbDEujtxji7d2-BBrLq3QfKJU4k30WF4wk2yzQeqDleo7UtWx3txE5uoRjR5QdRoDIq5ww-hw6q
> T42Kzvod9_06a3kywLBOx_Uf89GzXXztetww&__tn__=-UK-R-R&c[0]=AT2FJKoKQPKKDfoy0bK
> SvTFphlJXzXviJGcLtUyTxjYjK58ncIURXA3e1BjyNH8-FMIGjbdE70ykwz-e0mMrbGJqnwhV434
> PKPd5y_6AxhoiLkU-Qpdjmvixo9XwDiIcT2cjfaEaL3LDxIZWC2WWeGLvAdXNIIGvyd0Hfe7UGkN
> SYn2X3pA3wDSTTaHc1-S7faKMUU33goZB2JGfqaZxLRwJ2eI3 ) , my SA ultra's input RF
> switch chip U22 (AS179-92LF) has failed. This chip is so tiny it seems
> there is not a soldering iron or tweezer small enough to replace it. It's
> like a microscope-dependent repair! Has anyone had success with this
> repair, or is it just smarter to buy a whole new SA Ultra?
>
>
>
--
?
mfg
?
? Ing. Rainer Hantsch
??? (Firmeninhaber)
?
-------------------------------------------------
?ING. RAINER HANTSCH - Hardware & Software
?Khunngasse 21/20
?A-1030 Wien
?*** Austria ***
?
?Tel.: +43-1-7988538-0???? Fax : +43-1-7988538-18
?Mobil: +43-664-9194382??? Signal-Messenger (kein WhatsApp)
?
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Kindly suggestion: never use a graphite pencil as a pointer to components on a PCB. One might inadvertantly create a conductive path on the board without knowing it. This is just a general rule of thumb.
Based on the "fault finding" tab at , my SA ultra's input RF switch chip U22 (AS179-92LF) has failed. This chip is so tiny it seems there is not a soldering iron or tweezer small enough to replace it. It's like a microscope-dependent repair! Has anyone had success with this repair, or is it just smarter to buy a whole new SA Ultra?
|
Hi there,
?
I would second the recommendation to use a hot-air station for this repair.? With some practice beforehand, you can become proficient enough to do it relatively easily.? We have a cheap hot-air station at work and I've been able to do some very intricate work with it once my skills improved.??
?
A second method would be to use low-melt solder and a small soldering iron.? Low-melt solder has a much lower melting temperature than normal solder, so it stays liquified longer.? This allows all leads to be liquified at the same time so that you can remove the chip.? Here's what I'd recommend:? soak each lead with low-melt solder.? You're heating up the lead & "mixing" the low-melt solder with the existing solder on the lead, ultimately lowering the overall melting point.? If you want, you could even wick off the existing solder & then add the low melt.? But once all leads are soaked w/low-melt or the "mixture", move your iron around from lead to lead until all leads are liquid at the same time.? They will stay this way for several seconds, allowing you to remove the chip.? Normal solder won't do this.? As soon as you move to the second lead, the first one solidifies, and so on.? Next, clean the pads with solder braid & IPA - get them looking new so that all the low-melt solder is removed.? Then solder the new chip in place using NORMAL solder (not low-melt).? Low-melt is only for desoldering.
?
A microscope is extremely helpful, but we don't have one at work.? I've done numerous repairs like this with only magnifying goggles/glasses or a headband magnifier - i.e. something you can wear on your head to keep your hands free.? I wouldn't mess around with one of those alligator clip magnifying glasses on a stand, though.? You probably won't be able to see well enough, you only get one spot that's visible, & they're tough to position just right.? So if you don't have a microscope & don't want to invest in one, go with the goggles/glasses and do the repair in a well lit room.??
?
One more thing: use plenty of flux.? Flux is your friend when soldering.? If you don't use it, you'll get hit-or-miss solder joints, bridging, etc.??
?
I've learned a ton from watching Alex on Northridge Fix's YouTube channel.? He's no-nonsense and he gives great information.? Watch a few of his repair videos - any of them, don't look for "LiteVNA repair" because he hasn't done any.? He uses a hot air station and/or low-melt solder in nearly every video so even if he's repairing laptops, it'll be relevant to you.? If you watch a few of them, it'll help you decide whether to try this yourself.? I'm not associated with him, nor do I get any benefit from recommending him.? I've just learned a lot from watching him.
?
?
There are other good soldering channels out there on YouTube as well.? Mr. Solderfix comes to mind as another good option.
?
I wish you well!
?
Steve
?
?
?
?
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I managed to change U22 in my Tiny SA Ultra. I used an 852D+ hot air soldering station. Used hot air to remove old one and soldering iron and Ersin multicore? 23SWG solder to solder new one. Used a head band magnifier. Not the easiest thing I have ever replaced by far! As a result of my replacing U22 I have purchased a Digital microscope 1200X for the future. Take a shot at replacing it, if it all goes south, you can still get a new one.
On Tuesday, April 1, 2025 at 06:59:11 AM PDT, svkirk via groups.io <svkirk@...> wrote:
Hi there,
?
I would second the recommendation to use a hot-air station for this repair.? With some practice beforehand, you can become proficient enough to do it relatively easily.? We have a cheap hot-air station at work and I've been able to do some very intricate work with it once my skills improved.??
?
A second method would be to use low-melt solder and a small soldering iron.? Low-melt solder has a much lower melting temperature than normal solder, so it stays liquified longer.? This allows all leads to be liquified at the same time so that you can remove the chip.? Here's what I'd recommend:? soak each lead with low-melt solder.? You're heating up the lead & "mixing" the low-melt solder with the existing solder on the lead, ultimately lowering the overall melting point.? If you want, you could even wick off the existing solder & then add the low melt.? But once all leads are soaked w/low-melt or the "mixture", move your iron around from lead to lead until all leads are liquid at the same time.? They will stay this way for several seconds, allowing you to remove the chip.? Normal solder won't do this.? As soon as you move to the second lead, the first one solidifies, and so on.? Next, clean the pads with solder braid & IPA - get them looking new so that all the low-melt solder is removed.? Then solder the new chip in place using NORMAL solder (not low-melt).? Low-melt is only for desoldering.
?
A microscope is extremely helpful, but we don't have one at work.? I've done numerous repairs like this with only magnifying goggles/glasses or a headband magnifier - i.e. something you can wear on your head to keep your hands free.? I wouldn't mess around with one of those alligator clip magnifying glasses on a stand, though.? You probably won't be able to see well enough, you only get one spot that's visible, & they're tough to position just right.? So if you don't have a microscope & don't want to invest in one, go with the goggles/glasses and do the repair in a well lit room.??
?
One more thing: use plenty of flux.? Flux is your friend when soldering.? If you don't use it, you'll get hit-or-miss solder joints, bridging, etc.??
?
I've learned a ton from watching Alex on Northridge Fix's YouTube channel.? He's no-nonsense and he gives great information.? Watch a few of his repair videos - any of them, don't look for "LiteVNA repair" because he hasn't done any.? He uses a hot air station and/or low-melt solder in nearly every video so even if he's repairing laptops, it'll be relevant to you.? If you watch a few of them, it'll help you decide whether to try this yourself.? I'm not associated with him, nor do I get any benefit from recommending him.? I've just learned a lot from watching him.
?
?
There are other good soldering channels out there on YouTube as well.? Mr. Solderfix comes to mind as another good option.
?
I wish you well!
?
Steve
?
?
?
?
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Greetings,
?
I think the use hot air removal in this case, considering all the near by components, could be risky unless you happen to have the proper size hot air tool hood that fits the chip and contains the heat to the very small area. I would consider just nipping the leads off the chip body and then remove the remains of the leads, one at a time, using a fine tipped soldering iron and tweezers.
?
As the chip package is of the leaded type with just a few leads as shown in the photo, and is known to be defective (thus of no value) you might consider the following approach using at minimum the following list of special tools and supplies:
?
a) Magnification hood with LED headlight illumination that ensures a detailed view of the chip.
b) Miniature diagonal wire cutter plyers.
c) ?Teflon or similar tipped high temperature, low thermal conductivity tweezers.
d) Fine tipped, temperature controlled soldering iron.
e) Very fine solder.
f)? Isopropyl alcohol and Q tips?
?
1) Remove the chip body by using the cutters to snip off all the leads close to the chip body.
2) Using the very fine tipped, temperature controlled soldering iron heat and remove the remaining leads with the tweezers one at a time.
3) Carefully remove the remaining old solder on the footprint pads with solder wick.
4) Using the Q tips clean the footprint area with isopropyl alcohol.
5) Examine the footprint carefully and ensure all the pads are isolated from each other.
6) Whilst ensuring the correct chip orientation solder in the new replacement chip by just wetting the pads using a minimal amount of solder
7) Inspect the install to ensure no adjacent pins have been accidentally bridged with solder.
?
? ? ? I hope this info is found helpful and good luck!
?
73
Tom
VA7TA
?
?
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WARNING !!!
?
The suggested method of getting off the bad chip is very rude and dangerous!
This may be practical with bigger chips, but not with so tiny ones!
Not knowing if traces cross right below pins, I would be extremely careful with using any kind of cutter to cut off the pins. When the pin is cut, the blade usually hits the surface of the PCB and can hurt the trace below.
Also, the cutter bends the pin away from chip-body when it slides in between Chip-body and separated pin. This causes a lot of force to the soldering pad. If this ens in a lost solder pad (we talk here of almost microscopic dimensions(!), you can throw away the PCB.
If using a soldering iron is desired, I recommend bending a copper wire in U-shape, just wide enough to get the Chip-body in between. This way the copper is in direct touch with all chip pins at same time and the copper allows heating up all pins simultaneously (spreads the heat). Now apply so much solder/tin to the top of the chip-body that it reaches both sides of the "U". Wait until solder joins are molten, then pick up the chip and Copper-U with a fine squeezers.
It is wise to cover surrounding area with some tape (the yellow one for higher temperature) to protect it from tin drops.
But - honestly - hot air is definitely the better choice.???? -> I am talking of a hot air reflow workstation, not a hot-air-gun from supermarket.
Am Dienstag, 1. April 2025, 22:34:41 CEST schrieben Sie:
> 1) Remove the chip body by using the cutters to snip off all the leads close
> to the chip body.
> 2) Using the very fine tipped, temperature controlled
> soldering iron heat and remove the remaining leads with the tweezers one at
> a time.
> 3) Carefully remove the remaining old solder on the footprint pads
> with solder wick. 4) Using the Q tips clean the footprint area with
> isopropyl alcohol. 5) Examine the footprint carefully and ensure all the
> pads are isolated from each other. 6) Whilst ensuring the correct chip
> orientation solder in the new replacement chip by just wetting the pads
> using a minimal amount of solder 7) Inspect the install to ensure no
> adjacent pins have been accidentally bridged with solder.
>
> I hope this info is found helpful and good luck!
>
> 73
> Tom
> VA7TA
>
>
>
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On Wed, Apr 2, 2025 at 02:08 AM, Rainer Hantsch wrote:
But - honestly - hot air is definitely the better choice.???? -> I am talking of a hot air reflow workstation, not a hot-air-gun from supermarket.
Applying background heat to the PCB helps in using lower temperatures and reduces thermal stresses on the board and components.
Low-melting point solders like Chip-Quik also have their place in your rework arsenal.?
I use the paste; a surprisingly-small amount (tip of toothpick, heaping it on just makes a mess) will drastically lower the melting point of the solder, which just makes things much easier.
73, Don N2VGU
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Yes, you definitely need a microscope. If you're a hobbyist and you solder often you'll not regret buying a good microscope. Key thing is it has to be a normal optical microscope with at least 15cm~20cm of space between the optics and the work piece. It shouldn't have too much magnification. I believe my microscope has 0.5x and 1x objectives and the eyepieces are 10x. I also have 20x ones but I use them rarely. So a magnification of 5x is pretty good.
I like my microscope so much I do most of my soldering under it. I really like watching how tiny pads become molten.
Regarding this part if you don't have hot air the best way to remove it is either crush it with snips (GENTLY) or put a large ball of solder on a big chisel tip that will engulf the entire chip. Touch it and the moment solder melts it should suck the chip right into the ball of solder. It is very possible the ball will drop the moment you start lifting it so put a suitable shield in place (piece of cardboard) to move it between the pcb and the tip the moment you lift it.
If you have hot air youjust tape everything surrounding the part with kapton, blast it and grab with tweezers when you see under the microscope it became shiny(melted).
Soldering back is not that hard (with a microscope). You solder two opposing corner legs. Then you go after the rest. The easiest is to have a small tip (not the smallest, next size up) and go leg after leg. There is a technique where you do the entire side at once. I always have shorts afterwards.
You'll also need leaded solder in 0.25mm rosin flux wire (0.5mm may be OK) and so called bga flux. Make sure to wash it later (with ipa) as the thing is really corrosive.
I've replaced a tiny switch like that in a nanovna, but it was even smaller and had balls under for contacts. Still it was fine with hot air.
As others say. Be very careful if you choose to crush. Do not cut the legs. You will rip the pads off the pcb. Just crush the chip itself.
Good luck,
Based on the "fault finding" tab at , my SA ultra's input RF switch chip U22 (AS179-92LF) has failed. This chip is so tiny it seems there is not a soldering iron or tweezer small enough to replace it. It's like a microscope-dependent repair! Has anyone had success with this repair, or is it just smarter to buy a whole new SA Ultra?
|
Well, since over 10 years I'm very happy with my headband magnifier. Those days bought from RS. Article Nr. 606-989 looks approximately the same. It fits also over a pair of glasses. But (yet) I don't know what about the magnification. I'd have to check it in my lab. But approx. 2.7x - like that model offers, could well apply. I only don't remind that it was that expensive.? RS offers also a more affordable product that's available up to 3.5x (Shesto, not a RS PRO product) Its advantage above a microscope: better feeling of hands movements (and greatier viewing angle), in a word: less indirect handling experience.
However, sometimes I need to check solder efforts using a small eye magnifier x5 or x7, I mean the sort that is in a conical formed tube such that you can hold it by your eye surrounding. Not because I do so (often it simply falls down), but simply by helding it by fingers while looking at approx. 10-15 cm distance. The tubing helps reduce reflections from room light. Sometimes I uses this lens when I only have to use only one hand to re-heat a questionable joint with the solder tool (evtl. prepared with a bit application of Rosin paste.
On Wed, 02 Apr 2025 16:43:06 +0200, flynth via groups.io <flynth@...> wrote:
Yes, you definitely need a microscope.
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On Wed, Apr 2, 2025 at 10:43 AM, <flynth@...> wrote:
If you have hot air youjust tape everything surrounding the part with kapton, blast it and grab with tweezers
I prefer to use a more subtle approach, I turn my hot air station to near minimum airflow and apply background heat so that the PCBA is at perhaps 80C, too hot to touch.? I don't bother with Kapton and haven't blown a part away in years, surface tension is surprisingly strong.
Apply a sparing drop of flux to the part, ChipKwik if using.? Use a small air nozzle and hold it just above the part.? Turn it up HOT.? When you see the part melt, pick it up with your #7SA tweezers and discard it.?
Be patient, if you try to rush and lift the part prematurely you risk lifting a pad (or more), you will see the solder surface distinctly change when it liquifies.
??
Binocular magnification and BRIGHT illumination help a lot, high mag not so much, I usually end up at ~8X.?
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A client spent big $$ on a USB 'scope/display combo; it was useless compared to my Antscope from Amazon:
Monocular vision = no depth perception
Poor dynamic range, pitch black shadows, burned-out highlights
Poor resolution
Short focal distance = crowded workspace
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Way better and cheaper:??
Similar to this, mine came with a 0.5X objective lens to double the working distance
Wow, twice what I paid, but I'd still do it.
I also added the articulating arm, it now covers most of my workbench. ?
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73, Don N2VGU
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I managed to change my lna and input switch with a tiny iron and Chipquick removal alloy. Doubtless, I was just lucky but it can be done that way.?
Ross
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Donald S Brant Jr
