negative voltage regulator

Does shorting a charged tantalum in fact form a defect? They do get charged a lot more often than they get hot-shorted.

Am 24.05.2018 um 16:39 schrieb John Larkin:

I have made no tests, but a hard short can produce bigger current spikes than charging with probably some current limiting. Remember how rail guns work. Long precharge and then - kaboom!

I was wondering if it actually happens.

Tantalum failures are so erratic that it's difficult to test for them. Sometimes an entire reel seems to be bulletproof.

Easy, yes, but sometimes painful. I remember a producton tech where it popped, flew off and hissed through his shirt. The company bought him a new shirt ...

It might be different when at the end of the transient the cap is fully charged--the EDN "cap-astrophe" article on my website says that the failure surface microstructure looks exactly like an overvoltage failure, and that the thermal history of the part affects the voltage where that happens.

Cheers

Phil Hobbs

My VIXIA's clamped 14.5" up on a chem stand with +16 (+10 +4 +2) of mag lenses screwed together as a test to get a feel for things. So far the only minor glitch is some standard VIXIA icons that appear just inside the perimeter to frame the shot. Although my lab monitor has plenty miles left on it, it lacks an HDMI port. It's also connected to a KVM switch so there's no future in constantly disconnecting the KVM to connect the VIXIA and vice versa. My best bet for now is to just use an AVerMedia stick to connect the VIXIA to an open USB port on my video processing PC, fire-up the video software, and put the video feed into full screen mode. This is a sweet setup. The view is rock solid. When you want to zoom in you just lift your work and the VIXIA re-focuses.

Thank you, 73,

Thanks for the description. Doesn't your VIXIA have zoom? I have never heard of a VIXIA without it.

The Canon VIXIA HF R800 has 32x optical zoom and is currently on sale for CAD $279.99 at BestBuy in Toronto:

The VIXIA HF R70 has 57x zoom and is sold by Canon for USD $399.99. I'm thinking of getting one. 57X would be awsome, but I don't know if it would actually make sense for pcb work.

Newegg has some HDMI monitors as low as CAD $99:

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That's why active quenching circuits are popular, you kill the high voltage shortly after the SPAD has avalanched, and keep the voltage across it belo w breakdown for long enough for the charge carriers to go away before jacki ng the voltage up again above the value that will sustain avalanche break-d own.

It's supposed to give you less dead-time.

Another source that might be interesting is Kijiji. Here's a link to the Toronto region with several VIXIAs for around CAD $100:

As far as zoom capability, my VIXIA has 20X. I rarely go to the max, and never stay there long, so 27X or 32X should be more than adequate.

I'm starting to think that 57X may be overkill. Good for the WOW factor when showing a visitor, but useless in practise.

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Right, I'm going to a work shop this week and will get a better grip on the count rates and such. If the coincidence rate is low (~1kHz) then the dead time may not matter much. The dead time is now ~ 0.5 us. A factor of ten less should be fairly simple, he says naively.

George H.

My Canon VIXIA HF R800 does indeed have 32x optical zoom. Remember, my VIXIA sat on the shelf until now. This is all new to me. The W-T slide control is now used by me to zoom. The only minor nuisance that remains are the icons that appear around the view's perimeter. Although the icons don't block my view, they do bug me enough to at least perform a cursory investigation on how to turn them off. Thank you, 73,

Good info. Congratulations. You are making very good progress. Do you have a closeup lens, or does the HF R800 need one? What is your working distance?

You may want to get a polarizing filter from eBay, and a flat plate glass to keep solder fumes from clouding the lens. Your filter diameter is 43mm. Here is the user manual:

You can also place a small 3" fan to one side to blow the fumes away from the working area.

Once you get going, you may want to get a cheap HDMI monitor. It has much higher resolution than the tiny LCD screen on the VIXIA. You will be amazed at how much more clarity and detail the monitor gives. You don't need a new one. A minor scratch may be of no consequence. I just checked Kijiji, and they had some for CAD $20

Good Work!

Ex-VE3CKS, VE2BLB, F7CD, VE3CWF

The working distance is about 14". A 49mm to 43mm adapter enables me to connect all of my Pentax lenses, which include +10, +4, +2, and +1 magnification. The input path of my video feed is: VIXIA > AVermedia AV-to-USB adapter > W2016 Server > Videostudio The output path is: Videostudio > W2016 Server > KVM switch > 24" monitor Videostudio renders a video stream in full screen mode. So an HDMI video stream to a 24" monitor is essentially achieved without any HDMI. The VIXIA's 3.5mm AV jack is used instead of its HDMI jack. Thank you, 73,

You got me beat. My working distance is only 10"

Good job. Thanks.