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Replacement of damaged NanoVNA circuit board
#hardware
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I accidently transmitted 12w into my connected nanovna and caused some damage to the software or components, not sure but it cannot read SWR any longer. It still uploads firmware etc but does not function as it did in the past.
Is it possible to replace the entire main board with a new board? where can I get that replacement pls |
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On 5/20/22 11:35 PM, mbwilliams@... wrote:
I accidently transmitted 12w into my connected nanovna and caused some damage to the software or components, not sure but it cannot read SWR any longer. It still uploads firmware etc but does not function as it did in the past.There *is* only one board, so you're probably looking at just buying a nanoVNA, and having a spare battery and LCD display.? You might ask whoever you bought yours from if they'll sell you just the board, without the "case" or LCD. You probably cooked the bridge (CH0) or the 20dB pad (CH1), and maybe some downstream components (the mixers). They're readily available, but they *are* SMT devices and a bit tedious to replace. It would be interesting to know what actually cooked.? For instance did the SA612 mixer perform as a sacrificial fuse, or did the analog inputs on the audio chip also get fried. If you're interested, you can probably try to diagnose it if you have an ohmmeter, and an oscilloscope.? For instance, assuming you can "talk" to it, you can set a frequency and see if the synthesizer is putting out the two signals 5 kHz apart.? You can look and see if the output of the mixer changes when you change the termination on CH0. |
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I am interested if anyone figured this out, because I just fried mine nanoVNA SAA-2N just now. -_-!
I was building some homebrew amplifier. Before measuring that, I wanted to calibrate the test PCB before I put in my transistor. So I would solder different resistors on the board and take measurement. The board is not powered (completely passive). It was tedious, I got lazy and did not remove my nanoVNA while I solder. I had DC-blocking capacitors though and I got away doing that a few times before so I imagined it would be fine. But apparently it is not fine this time. Now if I just connect Tx to Rx port, I got high reflection (close to an open) and only -20dB transmission. Software part seems to work still, so I suspect RF front end was killed. I open the casing and took a look, but I don't want to make a rush decision and break it further. Also those EMI shields looks hard to remove. So does anyone have advice for me on what is the most efficient way to repair? And do you expect a soldering iron to have damage like this (I still don't fully believe it!) or is this something else? |
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maybe a spike killed the first switching chip (those are well known to burn up)
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dg9bfc sigi Am 02.10.2022 um 17:24 schrieb linhz0hz@...: I am interested if anyone figured this out, because I just fried mine nanoVNA SAA-2N just now. -_-! |
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If you measure capacitance between the AC cord to the Iron tip, you get about 200 pf.
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The AC voltage is capacitively coupled to the Iron tip unless you have a specially grounded IRON,(And have the Ground Connected) So the average soldering iron is a 200 pf cap plugged into 120 VAC going to your circuit.? Kent On Sunday, October 2, 2022 at 05:33:28 PM CDT, <linhz0hz@...> wrote:
I am interested if anyone figured this out, because I just fried mine nanoVNA SAA-2N just now. -_-! I was building some homebrew amplifier. Before measuring that, I wanted to calibrate the test PCB before I put in my transistor. So I would solder different resistors on the board and take measurement. The board is not powered (completely passive). It was tedious, I got lazy and did not remove my nanoVNA while I solder. I had DC-blocking capacitors though and I got away doing that a few times before so I imagined it would be fine. But apparently it is not fine this time. Now if I just connect Tx to Rx port, I got high reflection (close to an open) and only -20dB transmission. Software part seems to work still, so I suspect RF front end was killed. I open the casing and took a look, but I don't want to make a rush decision and break it further. Also those EMI shields looks hard to remove. So does anyone have advice for me on what is the most efficient way to repair? And do you expect a soldering iron to have damage like this (I still don't fully believe it!) or is this something else? |
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On 10/2/22 5:37 PM, KENT BRITAIN wrote:
If you measure capacitance between the AC cord to the Iron tip, you get about 200 pf.The typical Weller WTCP irons all have grounded tips. On Sunday, October 2, 2022 at 05:33:28 PM CDT, <linhz0hz@...> wrote: |
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I would also think that even if a tip did have capacitive coupling, unless the board had earth ground somewhere, that no current would flow . . . .kinda like a bird on a power lime.
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On October 2, 2022 8:38:18 PM CDT, Jim Lux <jimlux@...> wrote:
On 10/2/22 5:37 PM, KENT BRITAIN wrote:If you measure capacitance between the AC cord to the Iron tip, you get about 200 pf.The typical Weller WTCP irons all have grounded tips. --
Sent from my Android device with K-9 Mail. Please excuse my brevity. |
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Yes, and I have seem the ground pin cut off, and I have seen miss wired wall sockets.
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Just letting people know that simple/cheap soldering Irons can kill digital electronics.? Kent On Sunday, October 2, 2022 at 08:38:29 PM CDT, Jim Lux <jimlux@...> wrote:
On 10/2/22 5:37 PM, KENT BRITAIN wrote: ? If you measure capacitance between the AC cord to the Iron tip, you get about 200 pf.The typical Weller WTCP irons all have grounded tips.
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Working on 900 MHz patch antennas (copper foil for tuning and matching) with about 1 or 2 meter of coax to the (original) SAA-V2, I had 3 broken units (1 from my customer). All revived by replacing the switch ic directly at the input. Search in the nanoVNAV2 group for details on repair and how to add protection.
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Success, Reinier On October 2, 2022 5:24 PM linhz0hz@... wrote: |
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This thread may be helpful: /g/nanovna-users/topic/80361897#20422
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Reinier On October 3, 2022 8:06 AM Reinier Gerritsen <r.gerritsen@...> wrote: |
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The WTCP irons are not cheap irons. I have three of them at work. I can
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verify that the tips are grounded. I have a cheapie Weller 25 watt iron that I added a solder lug and a wire with an alligator clip on to one of the three screws that hold the metal heating assembly onto the plastic case. I use that th ground the tip. Zack W9SZ On Sun, Oct 2, 2022 at 11:01 PM KENT BRITAIN <WA5VJB@...> wrote:
Yes, and I have seem the ground pin cut off, and I have seen miss wired |
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I can envision the potential for lots of coupling due to either magnetic field or capacitive coupling at nasty power line harmonics which can extend out quite far in frequency.
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On 10/2/2022 11:24 AM, linhz0hz@... wrote:
I am interested if anyone figured this out, because I just fried mine nanoVNA SAA-2N just now. -_-! |
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If you want ESD protection on your VNA or tinySA refer to this group's thread. I ordered these ESD protection diodes and installed them in my two tinySAs and my nanoVNA. They work perfect.
/g/tinysa/topic/81827330#4676 |
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Hi Dave & Friends!
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What is the working voltage of ESD suppressor diodes? What model did you use? ?n mar., 4 oct. 2022 la 22:48, Dave via groups.io <dvfuller= [email protected]> a scris: If you want ESD protection on your VNA or tinySA refer to this group's |
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Thanks for the reply, Dave!
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I had not seen the exact model of the ESD diode in the link sent. I must have been careless... I asked the exact type because in NanoVNA the junction capacity is very important in order not to influence the measurements. I see in the catalog of this diode a capacity of 0.05pF, which is very good for this application. As for soldering, I have all the necessary tools for Safe ESD operations, good eyes (;-) with glasses) and a magnifying glass with light. Regards, Costin ?n mie., 5 oct. 2022 la 20:58, Dave via groups.io <dvfuller= [email protected]> a scris: I used Mouser PN 652-CG0603MLU-05E. All the information was in the link |
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On 10/5/22 11:45 AM, Costin R wrote:
Thanks for the reply, Dave!Interestingly, in this application low C is nice, but not necessary. The calibration process would take out the shunt C, just as if you had a foot of coax or twisted pair. The potential "bad" effects are two fold: 1) the shunt C reduces the signal level, so the sensitivity of the receiver is less. 2) it is a semiconductor junction, so the possibility of IMD is there. |
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I checked the VNA before and after the modification and I saw no problems with it. Believe me if those diodes had an effect it would have really had a problem with the tinySA. The diodes were only a couple of dollars and Mouser was great at getting them shipped out and I ordered eight of them because they were so tiny. If you have any questions read the thread I posted above.
Dave NL7QY |
Dave
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