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 Post subject: Alternative method for taking voltages
PostPosted: Dec Tue 09, 2014 7:37 pm 
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Kind of silly. But for those still a little uncomfortable probing around a live chassis or for those who have short meter leads or bulky meter leads/clips. With the radio unplugged, leisurely and safely hook up your jumper leads to the points you'd like to measure for voltages. Run the leads to your bench and tape them SECURELY down and separated from one another. You can label the tape with the test points. And leave room to jot down the voltages, or label with letters and then corresponding letters on a notebook. Then when you're ready. Fire up. Of course do not brisk these uninsulated connections with your arm or hand . Jot down the voltage. Then you can turn off radio. Unplug. And remove leads. Simple. I hate reaching into a live chassis. I'm just not comfortable enough yet, and my meter leads are bulky/awkward, which makes probing in a rats nest a little worrisome.

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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Tue 09, 2014 8:12 pm 
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Huh, I figured you were going to make recommendations like...

"Stick the tip of your tongue on it." (Sorta like you do when testing 9V batteries.)

:-)

Actually, its not a terribly bad idea. Just be careful not to bump those leads while they're taped down. FWIW/IMHO, I think I'd make certain the yellow & black on the left were definitely *not* hanging over the edge to help minimize risk of bumping them.

I do something similar when testing high voltage of any sorts, particularly TV's/CRT's.

Turn off the equipment.
Discharge the CRT, if necessary.
Hook the probe and meter up.
Make certain the probe is attached well. (My HV probe has a little hook attachment for the end.)
Step away, and power up the DUT. (Usually by flipping switches/adjusting the iso-variac)
Look at the meter, and note the measurement.
Power off/Discharge/Disconnect

The main thing I don't want to be anywhere near the HV while its "live".

David


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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Tue 09, 2014 8:41 pm 
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Joined: Jun Sat 09, 2007 8:14 am
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Location: Florida
Another way is to make some probe extensions using a pin jack and some stiff insulated wire. I have two of these, one about 4 inches long, the other 8 or so. Good for probing down in a chassis and for keeping fingers away from HV.

Some like to connect probes with power off between measurements. Years ago, I did this to measure an 800 V power transformer. When I turned power off there was a loud snap from the inside of my new VTVM and it quit working on ac. The inductive kick had caused an arc that burned a cap lead in two.

RRM


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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Wed 10, 2014 12:33 am 
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Be VERY careful when using those little jumpers in tube radios.

The jumpers I've encountered are only rated for 30 volts.

- Leigh

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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Wed 10, 2014 12:47 am 
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They were holding on just fine. The wire's around 20 gauge or so, could be sturdier, but no ill effects. Insulation seemed fine too. In time I will get myself some nicer quality leads. If anyone has any suggestions, lemme know.

However, they needed to be reworked/soldered at the gator leads.. Previously just crimped. Cheesy.. But fixed that.

Hey, what's the scoop on that tracer Leigh? :wink:

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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Fri 19, 2014 2:29 pm 
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I use these 6" grabbers.
http://www.ebay.com/itm/Pomona-4724-Max ... 7675.l2557
or
http://www.walmart.com/ip/POMONA-5830-2 ... 3b0a19946z


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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Fri 19, 2014 3:08 pm 
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+1 for those gadgets---but sold at WALMART???!!!

The OPs idea has a lot of merit--the only thing I woulkd worry about is RF behavior with all the extra capacitance / coupling

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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Fri 19, 2014 4:54 pm 
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Joined: Sep Fri 07, 2007 2:27 am
Posts: 5134
Location: Grand Chute, Wisconsin
pixellany wrote:
+1 for those gadgets---but sold at WALMART???!!!
Not at Walmart, but sold by Zoro, through Walmart.com.

Walmart.com wants to be the first place people look for items, so they have thousands of outside "Marketplace" vendors that they partner with to fill the voids. There is an option box on search pages to look only at items actually supplied by Walmart.com. I always check this box when searching Walmart.com, as I don't want any surprises later.

The Walmart "Marketplace" program is very confusing to a lot of people. The rules for your purchase change, even though you think Walmart being the seller would support the items they list on their site. They don't.

Walmart Marketplace Buying Options
Here's what you need to know about buying from our approved Marketplace Retailers:
Marketplace items are not returnable to Walmart.com or Walmart stores
You can buy Walmart.com and Marketplace items in the same order
It's safe - we don't share your credit card information with Marketplace Retailers
Marketplace Retailers ship the items you buy from them
Tracking details (if available) can be found in your Walmart account
Marketplace Retailers provide customer service for the items you buy from them

.


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 Post subject: Re: Alternative method for taking voltages
PostPosted: Dec Fri 19, 2014 6:10 pm 
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Location: Rochester, NY
I need to find me some of those grabbers. I remember you using them a while back Lou when I visited the club at St. Rose and have wanted some ever since!

Yep--I kind of figured draping wires around like that could wreak havoc, so your mileage may vary, but so far so good.

One thing to note is yes....to be very careful what leads you're using. I need some high quality test lead material and quality gator clips to use with that lead material. My leads are cheesy and it seems the clips get loose sometimes/the insulator over the clip actually squeezes them so they don't snap shut as tight as they should. ALSO--B+ voltage I've been OK, but last night I tried measuring across the output of an 80, ramping up slowly on my variac. Once it hit 300V I shut the show down and went the tough route with my quality fluke leads. I didn't want to subject those flimsy leads to much more than they could "potentially" handle.

Just use caution, be smart ,and if one way doesn't work, try another. That's all. :)

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