Posted on November 20th, 2014 3 comments
In my previous video I showed a tour of the Ness factory.
What you didn’t see is my talk with the head design engineer about the blown PCB (he didn’t want to be on camera), which they had seen and promptly invited me in for the tour and talk about it.
They confirmed that yes, the blown part was a 50V rated MLCC capacitor across the AC mains plugpack input used for noise suppression, along with the other two caps from each input to mains earth.
The two MOVs are used for the input protection.
They have never seen this issue before, and the best explanation we can come up with is as expected – it was not a surge (which would have been captured by the MOVs) but a one-in-a-million outlier on the capacitor mortality bell curve that:
a) Just so happened to fail short (fail open is another common MLCC failure mechanism)
b) Just so happened to fail high enough short to not blow the fuse in the plugpack but instead allow the plugpack energy to be dissipated in the capacitor for long enough to burn the board as it did.
c) Just so happen to continue to fail at the right short value for a sustained period of time.
Bottom line is they have used this circuit in probably over a million installed panels on many designs over decades and have not seen this before, so it’s a pretty rare event.
Incidentally the Bosch panels also use this exact same input circuit (stolen from Ness it seems)
The capacitor is actually a bit unnecessary in the circuit and they could actually just leave it out, and they will look into that possibility.
Two capacitors could be used in series for extra protection, and is another future design change possibility.
The plugpack is fused and should normally be adequate to protect against a failure such as this, so it’s certainly not anything close to a recall issue. Just one of those rare events.
They are certainly a professional outfit and do take product safety and reliability very seriously.
Onto other things:
The MOVs that are left out of the zone inputs are done deliberately to save cost (and are not needed) for the Australian market. The MOV’s are only fitted for the South East Asia market where severe and frequent thunderstorms are common. The inputs have the spark gap protection plus two levels of input resistor protection. And their testing (and a million+ panels in the field) show that the MOVs are not needed in local markets for regular lighting surges.
The light bulbs on the battery are indeed used for battery charge regulation. They a low cost and reliable option for this, and provide a visual feedback and protection for installers who like to short things out!
They don’t like the look of them on the board either, but it’s been a reliable system for them for several decades now.
As I suspected, the micro does still use some original assembly code from the early days, but much of the new higher level code is C.
And yes, they came good and replaced the panel for me!
Posted on November 19th, 2014 12 comments
The founder and CEO of Ness Corporation Naz Circosta takes us on a personal tour of the companies impressive worlds class surface mount and through hole manufacturing facility where they produce hundreds of different Ness security and automation products.
It’s no every day the CEO of a major company has the technical knowledge to take you on such a tour of their own production facilities!
He shows the Yamaha SMD/SMT pick and place machines, solder stencil paste machine, flying probe testers, optical vision inspection equipment, custom test jigs, and plastic ultrasonic welding machines. And also talks about buying a $1M Objet 3D printer, and the advantages of genuine high quality Fresnel lenses vs cheap generic ones in PIR sensor performance.
Posted on November 14th, 2014 13 comments
Dave investigates two very serious issues with jitter on the Rigol DS1000Z series oscilloscopes, including the DS1104Z and new DS1054Z
Some sort of modulated sampling/trigger jitter problem at 5 microsecond intervals (the “5us jitter problem”). And severe jitter with the AC coupled trigger mode, a problem which is also present on the DS2000 series scopes as well.
NOTE: So many people have been confusing AC trigger coupling with AC input coupling people will be more familiar with. This issue has *nothing* to do with AC input coupling, it is AC trigger coupling!
Posted on November 11th, 2014 23 comments
So I get an Ebay email alert for something on my watch list. An item that rarely comes up, I was excited!, but then comes
SCAM SIGN #1: The seller has zero feedback.
SCAM SIGN #2: The seller is in Mexico. Not to offend any Mexians of course, but it’s not the US or the usual Ebay countries.
SCAM SIGN #3: The item is priced vastly under what the going market rate would be. A “to good to be true price”, and the wording of the seller seems to indicate they know how much this thing is worth. But hey, it’s an auction, they might be relying on bidding frenzy (but how would a normal zero feedback ebayer know this game?)
But hey, ebay and PayPal have an excellent buyer protection system provided you play the game by their rules, so I figured what’s the harm in bidding (the protection (and almost everything o ebay) sucks for sellers, but for buyers it’s a dream).
Turns out quite a few people thought so to, and bidding went from a start of $99 into the 4 digit territory. But still very low for such an item, so clearly everyone was thinking the same thing, but still being cautious that it’s a scam. Otherwise the item would have gone for much much more money I’m sure.
But like I said it’s rare this item comes up, so I was willing to play along with the buyer protection scheme. There was a reasonable chance it could be legit, so I searched for other similar items so see if they ripped off the images or text, but didn’t find anything. And the text in the ad sounded like a legitimate owner who needed to sell. If it was a scam ad, they certainly knew know what they were doing and how to market this thing.
Turns out I won just a little bit under my maximum bid – awesome! Excited! But still knowing there is a very good chance this is a scam…
So I go to pay for the item using PayPal through the usual ebay checkout system to ensure buyer protection.
SCAM SIGN #4: The checkout fails! I get the following error from PayPal:
“This recipient does not accept payments denominated in US Dollars. Please contact the seller and ask him to update his Payment Receiving Preferences to accept this currency.”
At this point of course I know 100% that it is a scam. But I play along anyway just to see how they are going to do it…
I send an innocent message and get a response:
So I reply that it doesn’t work, and I’ve never seen this before etc. Then they send a reply:
And on top of that the item shows up with the familial “Payment Received” icon in my ebay account!
That message and the icon marking is of course confidence trick to make you think ebay ok’d this, when in fact any seller is simply able to mark any item they sell as “Payment Received”
NOTE HOW EBAY WARN YOU AGAINST THIS EXACT THING!
Then I find:
SCAM SIGN #5: I get a manual PayPal invoice in my email inbox. It’s genuine of course, not a fake PayPal site that will steal my login (another variation on the scam!)
So by now it’s clear how this scam works:
- They set up new ebay and payapal accounts
- A really good scammer would hack an existing ebay account, or increase the feedback by buying a ton of 99 cent items from other fake accounts of theirs etc, but this one was content with zero feedback.
- List something exotic but one that would have high demand, and do a really good job with the listing making out they are the owner who needs to sell it because it’s not needed any more.
- Deliberately set up the PayPal account in foreign currency so the (almost certainly US or other major country like Australia) buyers PayPal checkout will fail.
- Make it out they have no idea what’s wrong and that they are sending an invoice manually, and try to convince you that ebay ok’d this.
- Sucker pays the money and they vanish with it. Maybe they might complete the scam by sending you an empty box with tracking number, but they have their money, so they probably won’t bother.
So there you go, ebay scams abound, and this is just one of them, and it’s simply a matter of using some common sense to sniff them out, and following ebays advice and systems.
Don’t get caught up in the excitement of thinking you are getting that bargain or rare item you are after. Some even justify getting scammed by saying “well, I was willing to take the chance at that price”.
Posted on November 10th, 2014 8 comments
Part teardown, part repair, Dave looks at an Australian designed and manufactured Ness D16X alarm panel that has failed.
What’s that smell?
Can it be fixed?
How do you repair solder mask on a PCB?, or add solder mask to your own home etched PCB’s?
And another look at PCB spark gaps.
Previous PCB Spark gap video