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Re: [OT] Shocks in a large market. How to check ESD direction?
I like the ideas about the anti static heel straps.
How can one check the direction of ESD? How to find out if it's me being charged, or the furniture? On Sat, May 4, 2024 at 9:11?PM Bruce Atwood via groups.io <CCDman1@...> wrote:
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Re: [OT] Shocks in a large market. How to check ESD direction?
OK, I'll try to post again.
Try a simple experiment by wrapping a small damp rag around one of your shoes, and secure it with duct tape. Then wander around with the cart and see what happens. This can also be an ice breaker for conversations - but not with yourself. It will appear more interesting if you carry a clipboard and take notes. Walking around on well insulated surfaces will tend to charge you up, while a discharge path should undo it. You could try barefoot too but that's probably frowned upon in stores. Ed |
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Re: [OT] Shocks in a large market. How to check ESD direction?
It's been like this for at least a year (probably much longer) and the
staff and other patrons are experiencing shocks too. No one gives a crap It's any time of the day There aren't any other stores in the neighrborhood. But I own a storage room about 100m away and that has metal walls on a concrete slab and those don't shock me. I don't manage them at all. The best way I've found is to first touch the metal fixtures using my knuckles, where shocks don't hurt. But I'll often forget to do it. On Sat, May 4, 2024 at 7:43?PM Clark Foley via groups.io <clarkfoley@...> wrote:
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Re: [OT] Shocks in a large market. How to check ESD direction?
I suggest a casual investigation to learn from the employees what they might be experiencing. Do not jump to conclusions with a solution or lead them. Just ask if they are experiencing electric shocks as they work in the store and see where it leads you. Your might discover something interesting.
If they are getting shocked, look for details: Has anyone complained? Is anyone concerned? Has it always been this way? Is it all day long? Is it this way at other stores in the neighborhood? How do you manage or mitigate the shocks? |
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Re: [OT] Shocks in a large market. How to check ESD direction?
On 5/4/2024 12:28 PM, cheater cheater wrote:
My third theory is that this whole facility has a lifted earth I was wondering how people would approach diagnosing this problem, andI would investigate that supermarket for proper facility grounding using my Biddle Megger Earth Tester, model 250260. I use it for testing radio station facilities where proper grounding can be vital. If the ground resistance is too high there are a number of techniques to reduce it, including specialized techniques for areas with particularly low soil conductivity. -- Dale H. Cook, Retired AM/FM/TV Chief Engineer, Roanoke/Lynchburg, VA |
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[OT] Shocks in a large market. How to check ESD direction?
Hi all,
I frequent a large grocery market nearby and inevitably every time I go there I get electrical shocks. I walk around with a cart and often if I touch a metal fixture (fridge, mesh rack) I get a painful shock. Sometimes I get a shock if I leave the cart for a few seconds and then touch its metal mesh. I was wondering what everyone thought. At first I thought it would be ESD, but why would it be so extreme? It happens every time. I live in a place that's pretty dry - RH goes under 20% regularly - and being on a plain it has a lot of wind, which could create triboelectric charging. But I'm not really sure about this. I don't know which way the ESD happens. Is my body discharging into the cart? Is the cart discharging into my body? Is my body discharging into the racks or vice versa? How can one check the directionality of ESD? One theory about ESD I have is that the fixtures get charged and my body gets the charge applied to it. This however isn't necessarily true to me because eg today I got a painful shock from touching the inside metal surface of a fridge, and that's supposed to be earthed. Another theory is that as I walk around in the store, as I move around with the cart, that charges my body. I wear rubber sandals and the cart has rubber wheels. That would mean I'm a conductor, attached to a large antenna (the cart's mesh frame), moving through dry air, insulated from the ground. The ground is made out of some sort of high impact ceramic-ish tile. But then why would my own cart shock me just mere seconds after letting go of it? I was unloading my groceries for the cashier. My third theory is that this whole facility has a lifted earth potential. There's an industrial area nearby and they may be dumping a lot of current into earth which would create a situation where walking on the ground charges you, and then touching something that's low-Z to neutral discharges your body (in this case this would be the earthed fridges etc). I was wondering how people would approach diagnosing this problem, and how you would fix it if you had the ability to change anything about the facility at hand - more as a thought exercise, but if I figure out what's going on I'm going to write to the company. Thanks |
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Re: 503 HV Transformer
When I wound up with the 561 from my dad's company, 30 years ago, it had a replacement filament transformer. I discovered that, in fact, the problem was a breakdown in the filament winding, not a problem in the original power transformer. I slipped some shrink tubing over the offending wire and used the 'scope, without the flying transformer, for many years. Right now it is, sadly, sitting without its HV transformer. It had a hard failure and was immune to baking. I've wound a new one but have not gotten around to potting it, 50-50 paraffin/bees wax. Someday.
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Re: Keithley anyone?
I'm assuming the failed FET is in a metal can, if so the failure could be tin whiskers. Several cures have been discussed in TekScopes recently. The simplest was to rap the can to mechanically dislodge the offending whisker. More in the last resort category was finding a short and fusing it with a voltage low enough to not damage the semi when the short disappears. 1st step is to ohm out the device to see if there is a short. Good luck.
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Re: 503 HV Transformer
The vert front ends are 8393 Nuvistors and they are enclosed in a metal shield at the front of the scope.
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Hoping that will be enough, have to wait for the transformer to know for sure. ChuckA On 5/4/2024 11:36 AM, Dave Wise wrote:
"Other circuitry" is a risk too. The field can induce voltages in nearby wiring, so you want to stay away from the amplifier front-ends. I had trouble with this when I was modifying a 500-series Type W plugin to use 6DJ8's instead of 8416's. --
See Early TV at: www.myvintagetv.com |
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Re: 503 HV Transformer
"Other circuitry" is a risk too. The field can induce voltages in nearby wiring, so you want to stay away from the amplifier front-ends. I had trouble with this when I was modifying a 500-series Type W plugin to use 6DJ8's instead of 8416's.
Dave Wise ________________________________ From: [email protected] <[email protected]> on behalf of ChuckA <chuck@...> Sent: Saturday, May 4, 2024 8:28 AM To: [email protected] <[email protected]> Subject: Re: [TekScopes] 503 HV Transformer Yep, Gonna mount it on the opposite side of the CRT, full metal plate between them. Have a oversize temp transformer there now with no issues. ChuckA On 5/4/2024 11:22 AM, Dave Wise wrote: Before you drill mounting holes, experiment with orientation in case the field gets into the CRT or other circuitry.-- See Early TV at: www.myvintagetv.com<> |
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Re: 503 HV Transformer
Yep,
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Gonna mount it on the opposite side of the CRT, full metal plate between them. Have a oversize temp transformer there now with no issues. ChuckA On 5/4/2024 11:22 AM, Dave Wise wrote:
Before you drill mounting holes, experiment with orientation in case the field gets into the CRT or other circuitry. --
See Early TV at: www.myvintagetv.com |
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Re: Keithley anyone?
I've got a older 155 analog voltmeter. My favorite analog bench voltmeter.
1 microvolt to 1000 volt full scale, zero center, battery powered. Unfortunately, one of the chopper fets in the input circuitry died and I have no idea what they are. I keep my eyes open for another unit for sale.... On Sat, May 4, 2024 at 9:20?AM Dave Wise via groups.io <d44617665= [email protected]> wrote: I have a 179 bench DMM also. I usually leave it running because I'm |
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Re: 503 HV Transformer
Before you drill mounting holes, experiment with orientation in case the field gets into the CRT or other circuitry.
Dave Wise ________________________________ From: [email protected] <[email protected]> on behalf of ChuckA <chuck@...> Sent: Friday, May 3, 2024 9:30 PM To: [email protected] <[email protected]> Subject: Re: [TekScopes] 503 HV Transformer To finish this thread the problem ended up being leakage from the CRT filament winding in the LV transformer. Seems I didn't "hear" Alberts description of the problem until I got an email from Ferrous Steinka and the light went on. I removed the CRT leads from the LV transformer and all the voltages from the HV transformer came on and stayed on. I connected a spare transformer I had to the CRT leads and now have an excellent display on the CRT. I was able to find a NOS 6.3V transformer with 3KV isolation for $5 that should fit on the bottom of the scope cabinet. And another TEK scope joins the "herd" Thanks to everyone who shared their ideas on fixing the problem ChuckA -- See Early TV at: www.myvintagetv.com<> |
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Re: Keithley anyone?
I have a 179 bench DMM also. I usually leave it running because I'm always using it to check this and that.
I also have a 147 Nanovolt Null Detector. After I capacitor-discharge welded all the crimp connections, it works well AFAICT but I don't have the cable and it turns out I'm not enough of a volt-nut to make proper use of it. I'd rather have a 155 or an HP 419 or a Fluke 845. Dave Wise ________________________________ From: [email protected] <[email protected]> on behalf of jmr via groups.io <jmrhzu@...> Sent: Saturday, May 4, 2024 6:24 AM To: [email protected] <[email protected]> Subject: Re: [TekScopes] Keithley anyone? I've got a Keithley 2015THD DMM, and I also have a basic Keithley 2000 DMM. I've also got one of the Keithley 2200 programmable power supplies plus another 2200 that needs to be repaired. I usually operate all of these remotely via GPIB although the 2200 also supports USB. |
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Re: Keithley anyone?
I have some Keithley too: some 7001 fresh refurbished by me and waiting for
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any hand-made board :) And Keithley 230 (not sure regarding working). I switched it on about a 15 years ago. Peter сб, 4 мая 2024?г. в 16:24, jmr via groups.io <jmrhzu= [email protected]>: I've got a Keithley 2015THD DMM, and I also have a basic Keithley 2000 |
Bill Riches
Dale H. Cook
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