Siglent SDS1202X-E compensation issue (and other manufacturers ?)

[Paul Moir]

FWIW the solution suits me fine.  Honestly I'd rather this than shipping out my 'scope.  But I wonder if we can get some replacement "Warranty void if removed" stickers from Siglent?   

[Diabolo]

Hello,


I bought my oscilloscope in Germany, how do I get the capacitor without having to return the oscilloscope for hidden defect (DIRECTIVE 1999/44 / EC OF THE EUROPEAN PARLIAMENT AND THE COUNCIL of May 25, 1999.)
There is also the solution to cancel the sale for hidden defects and to be reimbursed without charge.
However, if I can get the capacitor 3.9 pf 500V NPO for free (or at the right price) to make the change myself, it's ok.

What is the original value of CB106 ? To replace CB106 with an added value of +/- 4pf ?
Adding 1 or 2 (or more) picofarad in // CB106 would correct a little the default

Calibration certificate supplied with the device !!

Regards
Diabolo
----
Capacitor 3.9 pf 500V SMD 1206 NPO => C1206CRNPOBBN3R9
https://www.mouser.fr/ProductDetail/Yageo/CC1206CRNPOBBN3R9/?qs=sGAEpiMZZMsh%252b1woXyUXjyKgiPHH4l74keS21JCSpD4=

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:1999:171:0012:0016:FR:PDF

https://www.eevblog.com/forum/testgear/siglent-sds1202x-e-compensation-issue/?action=dlattach;attach=360433;image

[tautech]

What is the original value of CB106 ?

It measures ~16pF in circuit.

To replace CB106 with an added value of +/- 4pf ?

No, it will be much easier to add the 4pF cap onto the vacant/unpopulated C*105 position.

There are two caps to add, one for each channel in the C*105 position. CA105= Ch1, CB105= Ch2

Adding 1 or 2 (or more) picofarad in // CB106 would correct a little the default

The C*105 4pF cap is paralleled with C*106 and to add C*105 is the simplest lowest risk solution.

Yes some elaboration on the front end calibration would be nice.  I too assumed this step should be performed without probes (coax only), but reading it again it would make more sense to use middle-adjusted x10 probes.

No. Connect a function generator directly with a coax cable! The adjustment is for the input circuit's capacitive divider and not the probe.

Correct.

[TK]

No, it will be much easier to add the 4pF cap onto the vacant/unpopulated C*105 position.

There are two caps to add, one for each channel in the C*105 position. CA105= Ch1, CB105= Ch2

C105 is paralleled with C106 but left unpopulated... is this a common practice on DSO front ends?

[tautech]

No, it will be much easier to add the 4pF cap onto the vacant/unpopulated C*105 position.

There are two caps to add, one for each channel in the C*105 position. CA105= Ch1, CB105= Ch2

C105 is paralleled with C106 but left unpopulated... is this a common practice on DSO front ends?

I've no idea if it is or isn't.
From a design POV, it's good practice should part of the circuit should need trimming as it does in this case.

If you look at Dave's teardown image you'll see a good # of unpopulated positions, R's and C's.

[Diabolo]

Hello,

Looking unpopulated positions are always in // with a component. Certainly to finely adjust a precise value but unused value in the SDS 1202X-E.

Breaking the warranty band to "improve" on the NEW device to obtain a correct product is no good for Siglent and members will need to better target their future purchases.
Can the modification alter the accuracy of other measurements, or bandwidth ?

What does Siglent intend to do for abused buyers ?

Will Siglent supply the 2 capacitors for free on presentation of the purchase invoice for the SDS 1202X-E? It would be a gesture a minimum.
Out of respect for the buyers, Siglent should set up an email link to obtain the free 2 capacitors and a new guarantee band.

As for the calibration certificate that comes with the device, it only has the value of ink to print it, or to light the fire in the chimney !!

Sorry for my English, I correct the text with a translator.


Diabolo

[Chris-G]

OK, so we have a solution to this problem.  However I see the solution more of a problem than the original problem!!!!

Firstly, where the hell do you get a small quantity of 4pF 500V 1206 capacitors from.  I've looked through my normal suppliers Farnell (Element 14), RS, Digikey etc and not surprisingly they don't supply them.  They are out of stock at other suppliers and even if they were in stock I would be expected to buy a reel of 4000.

Secondly, and this is the really big problem, is that any rework by myself will no doubt invalidate the 3 year manufacturers warranty.  Even If Siglent were to say that the warranty would be honoured after the modification, it would still screw up my rights under the Sale of Good Act and Distance Selling Regulations, (UK).

Thirdly, the lack of the calibration label and an invalid calibration certificate would no doubt reduce the resale value of the instrument.

Although the rework to add the capacitors would be a doddle to do (If I had the capacitors), I think I will contact my supplier to see what he has to say.

If Siglent have applied this change to later production of this model, then they should product recall existing units to have the modification and recalibration done, (or at least offer a free service to those that want it [including all shipping costs]).  Otherwise all Siglent will have done is to use the early buyers of this product as free hardware beta testers.

Additional thought...   Won't adding components screw up the CE certification?

[exe]

Firstly, where the hell do you get a small quantity of 4pF 500V 1206 capacitors from.

I'm pretty sure this is not a problem. I don't think size is important in this case (take 0805 or 0603). May be even capacitance is not that important and, say, 3.9pF or 4.1pF would be good-enough. But Siglent has to better specify requirements (at least capacitance, tolerance, voltage rating) and, hopefully, a list of approved parts. I wouldn't expect frequency response to be an issue, but I'd check with the datasheet just in case. Kemet, Murata and AVX provide impedance curves. DC bias should not be a problem for such capacitors.

At the end, no oscilloscope is perfect and no two scopes show the same picture.

[tautech]

Firstly, where the hell do you get a small quantity of 4pF 500V 1206 capacitors from.

I'm pretty sure this is not a problem. I don't think size is important in this case (take 0805 or 0603). May be even capacitance is not that important and, say, 3.9pF or 4.1pF would be good-enough. But Siglent has to better specify requirements (at least capacitance, tolerance, voltage rating) and, hopefully, a list of approved parts. I wouldn't expect frequency response to be an issue, but I'd check with the datasheet just in case. Kemet, Murata and AVX provide impedance curves. DC bias should not be a problem for such capacitors.

At the end, no oscilloscope is perfect and no two scopes show the same picture.

Replacement cap specs and suitable parts are listed in the rework instructions I posted.
The caps must be 500V rated to preserve the scope's 400V rated inputs.
Good luck finding to 0805 500V rated ceramic SMD caps.

[rf-loop]

Firstly, where the hell do you get a small quantity of 4pF 500V 1206 capacitors from.

I'm pretty sure this is not a problem. I don't think size is important in this case (take 0805 or 0603). May be even capacitance is not that important and, say, 3.9pF or 4.1pF would be good-enough. But Siglent has to better specify requirements (at least capacitance, tolerance, voltage rating) and, hopefully, a list of approved parts. I wouldn't expect frequency response to be an issue, but I'd check with the datasheet just in case. Kemet, Murata and AVX provide impedance curves. DC bias should not be a problem for such capacitors.
.

They are specified.
And DC bias, of course not. Dielectric is C0G, not X7R shit

First, PCB is made for 1206 size. There do not need thinking if this or that is ok. Ok is 1206. Period.
Tolerance is specified. Named Vishay capacxitors have +/-  0.25pF tolerance.
Voltage. Specified. As can read named Vishay capacitors have 500V (CXLT) or 630V (CXET)
Recommended Vishay parts
VJ 1206 A 3R9 CXL...   size 1206, C0G (NP0), 3.9pF, +0.25pF, Ni barrier Tin coat, 500V (this is mandatory minimum without exeptions)
VJ 1206 A 3R9 CXE...   size 1206, C0G (NP0), 3.9pF, +0.25pF, Ni barrier Tin coat, 630V

[exe]

Replacement cap specs and suitable parts are listed in the rework instructions I posted.

Sorry, I missed that post.

I assumed a 4pF capacitors should be common as dirt. To my big surprise, these capacitors are much rarer than I expected when it comes to this voltage.

[Diabolo]

Hello,



https://www.mouser.fr/Passive-Components/Capacitors/Ceramic-Capacitors/_/N-5g8m?P=1z0wpt7Z1yx4arcZ1yxbokaZ1z0spi1Z1yzmoty

https://eu.mouser.com/Passive-Components/Capacitors/Ceramic-Capacitors/_/N-5g8m?P=1z0wpt7Z1yx4arcZ1yxbokaZ1z0spi1

Condenser can be sold individually.
Make a bulk order to lower shipping costs.


Shipping costs are high, a member can make a large order of these capacitors, and dispatcher in single envelope after payment of a fixed price by Paypal of the buyer.

Diabolo

[TK]

Unless you run a complete regression test on the fixed scope, you are not sure what this fix is going to break down the path... I wouldn't do it being the original issue a minor one.

[nctnico]

Unless you run a complete regression test on the fixed scope, you are not sure what this fix is going to break down the path... I wouldn't do it being the original issue a minor one.

Now you are being overly worried. A single capacitor somewhere at the input isn't going to cause a malfunction of the oscilloscope for sure or screw up it's calibration beyond what a self-calibration can't compensate for. An oscilloscope is not a high precision instrument to begin with.

What would concern me more is that in order to do this fix you need an ESD safe workstation (at least an ESD mat, wrist strap, ESD safe soldering iron) and good soldering skills.

[exe]

I'd also suggest be careful with not leaving flux on the board.

[TK]

What I am trying to say is that if anything weird happens after the fix, you will not be sure if it was the fix or it is a new bug and you will end up removing the caps just to verify, soldering them back... Maybe it breaks some calibration at different settings.

[rf-loop]

What would concern me more is that in order to do this fix you need an ESD safe workstation (at least an ESD mat, wrist strap, ESD safe soldering iron) and good soldering skills.

This IS real concern when who ever with what ever knowledge and experience and skills start this kind of work. Yes even when work is so simplex that need only add 2 small capacitors.

For experienced people/professional this is piece of biscuit what can do with left hand alone but for people who do not know how low his skill and knowledge is, there is so many things what may lead problems and trap is trigged. I have seen so many things where someone have example disconnected flat film cable and assembled it again. After then can ask just; why hell you did this total disaster.

ESD is more fun than many think. After ESD it can work just normally and then people think that all was ok. But he do not know there is now time bomb inside some circuit---tick-tack-....tick-tack...  ESD Induced Latent Defects.

Also these some cable connections need handle with skills and care.

Edit: Quote repaired

[nctnico]

ESD is not to be underestimated for sure. Several decades ago I sold self assembled PCs every now and then. Due to space constraints I assembled one PC in a non-ESD safe environment. Almost every part of that PC failed within the warranty period!

[Diabolo]

Hello,
Heat the soldering iron, then unplug it to make the solder with the hot tip, it is also a solution.
Personally, I have a soldering iron running on Li-ion battery, so no problem for me.
There is (?) Also the solution to manufacture these capabilities with "pigtail" by twisting 2 electric wires, or use 50 ohm 2 mm teflon cable and cut to the right length to get the right capacity in pf.

Diabolo

[nctnico]

Hello,
Heat the soldering iron, then unplug it to make the solder with the hot tip, it is also a solution.

No it is not because it can be still have a static charge.

[Diabolo]

Before welding we touch the tip of the soldering iron with the mass, and presto ! 

[nctnico]

Before welding we touch the tip of the soldering iron with the mass, and presto ! 

And then you move your arm to build up a new charge.

[StillTrying]

I would think shorting the BNC input, or putting a 50R termination on it, would help protect the input components from static while you're "welding" the cap. in.

[nctnico]

I would think shorting the BNC input, or putting a 50R termination on it, would help protect the input components from static while you're "welding" the cap. in.

Nope. ESD is exaclty like lightning. It is a charge which discharges through the path with least resistance. The only thing which helps is keeping everything at the same ground potential = at least an ESD mat, ESD safe tools and a wrist band/ground strap.

[StillTrying]

Nope. ESD is exactly like lightning. It is a charge which discharges through the path with least resistance.

A short to the equipment's GND is going to be hard to beat.