Honey, I fried my signal generator?

campbellm254 · Post by **campbellm254** » Thu Jan 13, 2011 9:00 pm

I have a V2 Nano.

The purpose of this post is two-fold, firstly a warning to take care with this part of the scope and secondly seeking some advice.

Last night, I mixed up the cables and exposed the signal generator output to a +/- 10v AC analog signal I was measuring. Since then, the frequency generator output has been compromised. I can still see the signal, but its amplitude is way down.

Looking at the schematic, I am almost sure I have fried the output stages of the 74HC125 that directly feeds the signal generator output. The spec for the chip suggests that it would not be impressed with the voltage range it was exposed to.

The chip looks like it could be replaced pretty easily, however, I don't want to go hacking at the PCB if its unlikely to be the point of failure.

Any comments? Has anyone else had this experience?

@Seeed. This was very easy to do. I think if this is a vulnerability, you should either

- add a protection circuit or
- change one of the plugs/sockets to a different kind entirely or
- at least make the jack plugs a different color.

esp · Post by **esp** » Thu Jan 13, 2011 10:11 pm

Sorry for the confusion! In the latest batch, one probe is white/black and the other is red/black.

You may send it back to us for replacement. Thanks for addressing the issue!

campbellm254 · Post by **campbellm254** » Fri Jan 14, 2011 10:21 pm

@ESP Thank you for the offer of returning it.

I may well take you up on the offer, since calibration will be an issue without test signal.

However, I do not think I can live without the scope right now (there, that shows how much I like it

). How about I order a Quad and return this Nano to you for replacement when it arrives?

owenix · Post by **owenix** » Thu Mar 24, 2011 10:59 am

I am having a very simular issue with the sig-gen. How was this resolved? I have seen threads stating u7 & u9. http://www.seeedstudio.com/forum/viewto ... +generator What should i look for to test this?
Thank you

campbellm254 · Post by **campbellm254** » Thu Mar 24, 2011 10:30 pm

Hi owenix,

I never got around to doing anything about it yet. I find my DSO too useful to give up for the time it will take to return it.

I suspected some of the gates in U9, but since I have only the DSO I was unable to confirm that, not wishing to try to use it on its own circuits.

Georg · Post by **Georg** » Fri Apr 01, 2011 10:13 pm

Hi,

same thing for me. I also must have mismatched the gnd and signal line of the signal generator and fried it in the process. I actually can't exactly retrace what I did but the signal generator seems gone. I have actually replaced the 74hc125 in the meantime and it didn't help. I am not exactly sure what happend, I will have to have a closer look on the datasheet of the chip and the schematic of the dso nano but I guess it killed the output pin of the controller. I think I will do a blog post on that topic soon to share what I found out and also help seed to maybe improve the circuit. It's really a shame ... the DSO is not a bad product but I think there are some serious design issues. A simple protection diode for less then 0.05$ would be sufficient to protect the board and there is enough space left.

Cheers,

Georg

lygra · Post by **lygra** » Fri Apr 01, 2011 11:53 pm

Georg wrote:Hi, same thing for me. I also must have mismatched the gnd and signal line of the signal generator and fried it in the process.

A temporary work around for all other users would be to use an audio cable when connecting the generator to the input jack of the Nano; I do this because it is both safer and quicker. The other interim solution would be to never connect the ground lead of the signal-in cable to the ground lead of the generator cable. It is dangerous connecting the signal cable ground to the generator cable ground for if they get reversed then you have shorted out the generator. The Nano circuit board already provides this ground connection.

Georg · Post by **Georg** » Sat Apr 02, 2011 4:21 am

OK, actually I solved my problem at least. It was indeed the 74hc125 which was dead. After I had replaced it I had a bad solder connection therefor I was aware that it worked again.

I will post an description of the problem/solution here as soon as possible, hopefully tomorrow. Hope that will help other people.

Georg · Post by **Georg** » Sat Apr 09, 2011 2:32 am

OK, you can find all information about my fix here in my blog

http://www.electricalbreakdown.net/

Have fun!

Georg

Danny Berry · Post by **Danny Berry** » Sun Aug 14, 2011 10:11 am

Hi George,

I couldn't get this link to work? I got a .com..but didn't see a blog or post about Nano Fix?

Thanks,

Danny

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Honey, I fried my signal generator?

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