[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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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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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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The vert front ends are 8393 Nuvistors and they are enclosed in a metal shield at the front of the scope.
Hoping that will be enough, have to wait for the transformer to know for sure.
ChuckA
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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.
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.
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<>
--
See Early TV at:
www.myvintagetv.com<>
--
See Early TV at:
www.myvintagetv.com
|
"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.
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<>
-- See Early TV at: www.myvintagetv.com<>
|
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
toggle quoted message
Show quoted text
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.
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<>
--
See Early TV at:
www.myvintagetv.com
|
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
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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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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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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I have some Keithley too: some 7001 fresh refurbished by me and waiting for any hand-made board :) And Keithley 230 (not sure regarding working). I switched it on about a 15 years ago. Peter §ã§Ò, 4 §Þ§Ñ§ñ 2024?§Ô. §Ó 16:24, jmr via groups.io <jmrhzu= [email protected]>:
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.
|
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.
|
Re: Dennis Tillman Tek 575 Curve Tracer Adapter PCB?
Thanks, I saw those but unfortunately I have a 575 which doesn¡¯t have the step gen output banana plugs on it like the 576/577/370. I do have an eico 667 kicking around that I don¡¯t use anymore since finding a tv-7, so Dennis¡¯ solution seemed ideal ¡ wouldn¡¯t have to build any test fixtures either
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Re: Dennis Tillman Tek 575 Curve Tracer Adapter PCB?
I have some extra's PCBs that I designed and had made. They are based upon Dennis' (and ChuckA's) design. You can see pictures of the finished unit here: /g/TekScopes/album?id=291888. My multiplier design (like ChuckA's) does not need a tube tester (just a curve tracer). Feel free to email me, if interested. There is another gentleman on here that sells a step multiplier that uses a switching PS to generate the high voltages.
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I have a 179 as my shop DMM. It is the only instrument I own which goes to the cal lab.
--
Dale H. Cook, GR/HP/Tek Collector, Roanoke/Lynchburg, VA
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On Sat, 4 May 2024, Ilya Tsemenko wrote: It's interesting -- I also have 263 waiting in queue for refurbishment and calibration as well as several 237 and 238 SMUs and couple of 6517A units :) Almost done with my HP/Agilent boat anchors, waiting for the last 4 to return from Keysight calibration, then will take on bunch of Keithleys. Which are Tektronix now, BTW, so they all probably belong here now. <+1>
I love Keithley's and repaired quite a bit of them, mostly DC/LF stuff.
Actually have 263 on bench too for some repairs. :)
BR,
Illya
On 05/04/2024 1:33 AM, Shaun M via groups.io wrote:
<Raises hand>
I do. I am working on a 263 at the moment. The best source for discussion I have found is the EEVBlog forum.
Shaun M
--- * * KSI@home KOI8 Net < > The impossible we do immediately. * * Las Vegas NV, USA < > Miracles require 24-hour notice. * *
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<+1>
I love Keithley's and repaired quite a bit of them, mostly DC/LF stuff.
Actually have 263 on bench too for some repairs. :)
BR,
Illya
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Show quoted text
On 05/04/2024 1:33 AM, Shaun M via groups.io wrote: <Raises hand>
I do. I am working on a 263 at the moment. The best source for discussion I have found is the EEVBlog forum.
Shaun M
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Also I am considering trades for in person meets.
I will also ship.
PM me for that.
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I have an SC502 that I want to sell. I see an SC503 going for $500 on ebay, but as we all know, ebay really likes to inflate prices.
I don't see many of these SC502s being sold so I'm not sure of a good price to sell it at. I don't want to sell it for too cheap, or have the price too high so some poor fellow spends too much money.
This SC502 works perfectly fine with one issue, the trigger source select switches offset the trace? This only happens to channel 2. Channel 2 is centered when sourcing the trigger from CH2. But when I switch it to CH1, it offsets the trace by about 1.5 divisions. I don't find this much of a problem though as I can just re-position the trace. If you fiddle around with the switch a little bit you can get CH2 to center again, but it's a difficult to hit sweet spot.
I'm sure this is just some bad contacts, but no matter how much deoxit I spray into it, it doesn't help.
Well, that's the only issue! Everything else works fine. Mag registration was calibrated, and the scope seems to be in decent cal. Could use some more work, but I'm selling this anyways and don't want to re calibrate it as I would have to disassemble my TM504 unit.
This unit was modded by me to add a function so that a DC504 frequency counter can measure the frequency being inputed into the scope. This is done by soldering a wire and siphoning off the trigger input signal and connecting it to the DC504 internal input through the TM500 power unit. You will have to desolder the 51 ohm terminating resistor though in the DC504.
The SC502 also had a recent repair:
I fixed it my replacing Q350 and it works perfectly now (apart from the trig source trace offset).
I'm thinking $300?? But I really don't have that much of an idea... I'm a bit of a push over.
I have fallen into the tek scope addiction and now have 7 tektronix oscilloscopes. I need to thin a herd a bit... Then use the new money to buy 3 more tek scopes
If you are picking this unit up locally, you are free to test it all you want before finalizing the purchase. I have an FG501 and PG501 unit you can use to test it.
I am selling only the scope. No TM500 power unit nor any cables.
Located in Carmichael, California, USA.
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<Raises hand>
I do. I am working on a 263 at the moment. The best source for discussion I have found is the EEVBlog forum.
Shaun M
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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
|
Dale H. Cook
Sergey Kubushyn
Benjamin Badrakh
Shaun M