Topic: [Ed: A thread in which ztex is blamed for a faulty board] (Read 4876 times)

Angry bastard mod here.

I've had multiple people report this thread. I think this is the kind of case where I tell both sides to just hire lawyers and sue, I'm locking the thread.

The boards where destroyed in idle mode, i.e. when the FPGA was not configured.

If the power supply dos not have bulk capacitors the voltage you measure is some kind of a mean voltage, usually the RMS voltage, not the peak voltage.


This would be another explanation.


As I wrote earlier, I sold several hundreds of this circuits, and Gusti is the only one I know who destroyed the regulators in this way.

A protection against such incidents would be a add a power supply. But if you are shipping all over the world you get a problem: different countries have different plugs and different voltages. Expensive international kits would have to be used and due to the size shipping gets even more expansive. Furthermore, most of these 1.15x FPGA Board's are used in clusters with a special power supply, see initial post of https://bitcointalksearch.org/topic/ztex-usb-fpga-modules-115x-and-115y-215-and-860-mhs-fpga-boards-49180.

Fuses give no additional protection since voltage regulators are over current protected.

Polarity protection by diodes would cost 0.5W on my FPGA boards (voltage drop of 0.65V @ 0.7A).

The USB-FPGA Modules 1.15x have low cost bulk capacitors (C3). The only job of this capacitor is to reduce the peak voltage in unregulated of unregulated power supplies. But this is only a small protection which helps to survive the most unregulated 12V supplies. Another not-100% protection for similar scenarios would be a Z-Diode in parallel. But I'm not sure whether these diodes exist.

A 100% protection is difficult / expensive (requires a voltage monitor circuit) and a transistor that switches of the power supply.

Unfortunately, there exists no protection against customers who destroy the second board in the same way after smoke came out of the first one.

I don't get it, didn't he say he measured 13.5 V open circuit on the regulator? Unregulated power supplies will always output a lower voltage with a load. So, no significant current at 13.5 V should have been applied. As soon as some current was drawn, the voltage would drop. Why would that have caused this damage?

My guess is that the polarity was wrong, although gusti said he checked that.

I'm very curious about what actually caused the problem, because we decided to include a barrel power connector at the last minute on our board and it makes me a little nervous that customers might pull out some crazy power supplies and plug them in. The 4 pin Molex connector will generally be safer, because the output from an ATX PSU will pretty much always be the same.

As a fellow hardware manufacturer, I sympathize with ztex here, but I hope something can be worked out to at least avoid this type of problem in the future. ztex, did you include any fuses or reverse polarity protection on the power input by any chance?

I excessively tested the circuits a while ago (on a Experimantal Board 1.3 which has the same power supply circuits): If an over voltage occurs the input voltage breaks through. I.e. the chance that FPGA and microcontroller survives is almost zero.

Replacing the 1.2V regulator is very difficult (and expensive) because bottom pads have to be soldered. It is impossible to do this by hand with lead free solder.

You are writing the FPGA Board has to support your power supply because your router does support it.

In don't understand this logic.

Gusti, plaese be son kind and remove my private date.

This forum in not platform for a personal vendetta.

Here is ztex. I'm producing FPGA Boards, see http://www.ztex.de. I also developed a FPGA board which is optimized for cryptographic applications like bitcoin mining: http://www.ztex.de/usb-fpga-1/usb-fpga-1.15x.e.html

Open Source Bitcoin mining software I released here: http://www.ztex.de/btcminer. I'm writing this because scammer usually invest time in developing Open Source Software for the products.

As Gusti wrote, he returned two boards 2 days ago. Both voltage regulators on both boards where destroyed. These voltage regulators are over current and temperature protected. The only way do destroy voltage regulators is by over voltage.

Since the valid range of 4.5 to 16 V (absolute maximum: 4.5 - 18 V)  is clearly stated on the products page (http://www.ztex.de/usb-fpga-1/usb-fpga-1.15x.e.html#con5), this is not covered by warranty.

Here is an image which shows the 3.3V regulator of one of Gustis board:


IMHO Gustie used an unregulated power supply. These things are called unregulated because their real output voltage is not equal to the value on the label. Gusti, did you measured the mean/RMS  voltage or the peak voltage?

The universal supplies from supermarket I mentioned (these one with switchable output voltage) are AFAIK always regulated. Therefore I recommend them as save.

Gusti, you wrote that smoke came out of one part of the first board. Why you destroyed the second board in the same way instead of asking me what is going wrong?


The 10% included a volatility margin and exchange + transfer frees. In these days the bitcoin price jumped by several percent within minutes.

If you would have used Paypal you would have received the board within the same time.

May be he just forgot to include warranty part in the board price.

Actually it's a bit strange that both boards have such damage, not likely to be a coincidence, especially when other users have good experience with them.
So it's may be either you plugged in some other, not suitable power supply, or the boards are not working because of something not related to power and "blown regulators" is just a reason not to replace/fix the product.

Would you repair the boards after someone calls you a scam in every thread ?
Imo it was too early to complain here.

I just checked over the schematics of the 1.15x product that your'e talking about...

From my perspective (several decades of analog and digital circuit design, EE), there are two possibilities if in fact the power supply is 'blown up'.

The supply is capable of handling input voltages of up to 16V:
     references: http://www.aosmd.com/pdfs/datasheet/AOZ1025DI.pdf  AOZ1025 Datasheet (1.2v Supply)
                     http://www.aosmd.com/pdfs/datasheet/AOZ1021AI.pdf  AOZ1021 Datasheet (3.3v Supply)
                     http://www.ztex.de/downloads/usb-fpga-1.15x.pdf  1.15x schematic, where a note is actually included on page 4 near the power connector (Input Voltage: 4.5..16V)

So, even if your supply is putting out 13.X volts, it's not really capable of hurting the power supplies.  It's possible that he means "blew up the capacitors", but I really doubt a guy as smart as ztex would use caps not rated to AT LEAST 16, and probably 25 Volts on the input.

So, as said, I suspect two possibilities here:
1) There was a real and significant problem with the board, and the output of the supply or supplies was essentially shorted.  Assuming ANY level of quality control, pretty unlikely.
2) You plugged in a power supply that was putting out > 16V (knowingly, unknowingly, admitting or not admitting).

If no shorts or problems can be found with the board, and he told you using a 12V supply was safe (he can't assume that you mean a 12V supply that isn't a 12V supply, by the way, and 13.5 isn't 12...), I wouldn't warranty the board either.  Sorry, but I wouldn't...  Now, I would offer a reasonable price for repair and retest, but that's me..

I strongly believe that the board was fed significantly more than 12, 13.5 and even 16volts..  I've worked a LOT with smps parts (although not the AOZ102X in particular), and they can usually stand quite a bit more than their rating for a short period of time anyway... In fact, the absolute maximum of the AOZ parts from their datasheets is 18V, meaning they can survive that for at least some amount of time...

Unless their is something else to this story that I don't know - I really don't blame ztex for not warrantying the board for you.  Should ztex provide (or at least sell) a compatible power supply - yeah, probably a smart move.. but He told you to use 5-12, you admit you used 13.5, and it won't actually fail until 18ish.. Something isn't adding up here...

I also invested lot of money, shipping costs and time with these boards, taking the risk that they are a new product with not much testing.
And everybody knows that new designs may have problems. So I expected a fair solution proposal by ZTEX, which seems Stefan is not willing to give.

He has excellent ratings everywhere you look around, he invested much time in wikis + he seems to be a very intelligent person. He can not afford to fück you over !

I can understand you. I had this sh!t with a turbocharger i purchased in the states. It failed after less than 8000 km and no warranty was given... that sucks at a price of 2k dollars 

I hoped that too, but his reply was that it was my only fault, and warranty does not apply.

You mean free of charge or not at all ? You can talk about everything in a fair way for both. Now the ball is at Stefan. I hope he does the right thing and is replacing the defective parts.

Sure, done that, voltage under load is 11.3 VDC

Lucky guy you have your boards up and running, hope they never stopped running because warranty will not cover.
My both boards are blown, power supply is a 3COM one, actually working with a switch.

Talked to Stefan all day long before posting here, his final word is that he will not give any solution nor a refund.
If that not a scam, what a scam is ?

Idle voltage may be not the same as with load. You should connect at least something like low-powered 12v lightbulb or some resistor.

So, you blow up two boards and then call someone a scam ? My board is working well at 12V. But we are talking here about "real" 12V from a power supply that cost at least as much as the "crappy" boards you purchased.   I'm almost sure that Stefan is going to replace the parts needed (at some cost as this was clearly your mistake imo). I had some initial problems with him that we had to work out but in my eyes that was something between me and him. A bit unfair that you come here and call him a scam. But that seems to be the way to handle things in the US.

Wrong. If the guy told him any after market power supply would work, then that is not fault by the consumer.
If they want to prevent this from happening, they need to include the power supply.
Why do you think all the stuff we have come with a power supply of its own?