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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Fri 14, 2014 2:08 pm 
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Location: Long Island
There's no need to buy an expensive gadget to measure leakage, unless you have to certify the results for a medical or institutional setting. The standard UL leakage test consisted of a sensitive AC voltmeter with a 1,500-ohm resistor and a 0.15-uF capacitor shunted across the input. We used an HP 400D VTVM for the purpose back in the day, but just about any modern high impedance DMM would work as well. The ground terminal of the meter is connected solidly to ground, and the input terminal goes to the probe which you touch to any conductive surfaces (including plated plastic) on the appliance in question. The appliance is energized, and the test has to be run twice, once with neutral and hot connected normally and again with them flipped. The ground prong on the appliance plug, if so equipped, has to be lifted during the test. Ohm's Law can be used to figure the actual leakage current if desired, but we just went by limits, i.e. 2.25 volts on the meter meant 1.5 mA through the resistor = failure.

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Fri 14, 2014 2:19 pm 
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Joined: Feb Tue 07, 2012 9:32 pm
Posts: 1789
Location: Middlesex,NJ
HI:

BOTH SENCORE UNITS WERE DESIGNED FOR THE TV SERVICE INDUSTRY.

LATER TV'S WERE TRANSFORMERLESS SO YOU HAD TO TAKE THE SAME PRECAUTIONS AS WHEN SERVICE RADIOS OR ANY OTHER ELECTRICAL DEVICE.
REMEMBER THEY HAVE A 4 AMP. LIMITATION.

SENCORE HAD A PRACTICE OF COMING OUT WITH NEW PRODUCTS EVEY COUPLE OF YEARS.
MOST OF THESE WERE VERY SIMILAR TO PREVIOUS UNITS BUT WITH MINOR CHANGES AND A DIFFERENT ENCLOSURE.

YOU WILL NOTICE THE ENCLOSURES FOR NEW LINE.ALWAYS TRYING TO GET THE TECH TO UPDATE WITH A FEW MIOR CHANGES.

LET US NOT FORGET ABOUT THE DIM BULB TEST AND RCA ISOTP.

WALTER-W2WIQ


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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Fri 14, 2014 3:16 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
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Location: Long Island
It might also be remarked that leakage testers were in vogue in the late 1970s and early '80s because there were rules being considered on Federal and state levels that would have required a leakage test be done on any consumer electronic product before a repair shop could return it to a customer. But by the time the few localities that did have such rules actually got around to enacting them, there were no TV repair shops left in business!

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Fri 14, 2014 3:46 pm 
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Location: Erie, PA
Chris summed it up well in the one post. The only real advantage these things offer is having an all-in-one in a good looking compact case. Not worth paying up the wazoo for a decent one IMHO, and any that are priced realistic always seem to be all beat up. For much less you can grab a variac, an isotap, and a P3 Kill-A-Watts meter, the advantage is you can separate those three items for other uses if needed.

-Mark-

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Fri 14, 2014 9:21 pm 
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Location: Lexington, KY
For an affordable all-in-one unit I agree with Dawn and recommend the Sencore PR-57 or the BK 1655. I had better luck finding a clean (and affordable) 1655 on eBay and have been happy with it... easy to service and calibrate.

If you want separate components look for a variac like the General Radio W5MT, an RCA Isotap for isolation, and a P3 Kill-A-Watts meter like Mark suggested.

I think I'd recommend the separate components starting out. Later if you get an all-in-one and it has problems you'll have the separate pieces to fall back on, plus it's nice having a more portable variac to tote around.

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Sat 15, 2014 4:26 am 
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Joined: Jan Thu 01, 2009 6:58 am
Posts: 267
How about these[code][/code]

http://www.alltronics.com/cgi-bin/item/ ... --Isolated

http://www.ebay.com/itm/ADJUST-A-VOLT-i ... 43c57a789a


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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Sat 15, 2014 7:22 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 4066
Location: NJ, 07645
darkwaterdevil wrote:
Variac
or
Sencore PR570 Variable Isolation Transformer & Safety Analyzer



I have 2 Sencore PR57's on my bench and I would not trade them for any other unit. They both work flawless.


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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Sat 15, 2014 10:26 pm 
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Joined: Sep Thu 23, 2010 6:37 am
Posts: 9532
Location: Powell River BC Canada
Just a few things I do with my Powerite, is powering up lightbulbs, and watching charging rates
of batteries.

The light bulbs are old , some made 100 years ago or more. Others, have markings that are hard to
read, and I want to gently know the wattage.

As to the batteries, if I plug the wall wart into the Powerite, the line current will reflect the
rate of charge.

Another function is the settable current trip, which works at any AC voltage. Ever try powering
up a built in intercom unit that runs off doorbell wiring ?

It is hard to know what Sencore is doing these days. A while ago I left a message about a part I
needed for an instrument I bought, and the person who left a message on my machine, was the same
Sales Engineer, I bought the TV stuff from 20 years ago.

I think that if Sencore got one of the American transformer makers to build the Powerite again,
they would sell everything they produced. After all, the thing is mostly copper and iron.

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Sat 15, 2014 10:44 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1717
Location: Chillicothe, Ohio 45601
I see no reason to get a PR570 for twice the price of a PR57. I had a PR57 in the past and liked it but sold it when I needed some money. Last summer I picked up a BK1655 for $70 shipped and it works as well as the PR57. I think the PR57 looked a little nicer though. The main reason I like the isolated variable transformers is just to save bench space but you would be hard pressed to find a good issoltion transformer and variac for the price of a BK1655.

Rod

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Mon 12, 2018 10:43 am 
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Posts: 322
Location: los angeles, california, usa
For reference, the B&K 1655A is actually a Global Specialties 1420 and can be purchased currently $73.26 less than the B&K 1655A. I have no relationship with Global Specialties or TEquipment.

https://www.tequipment.net/Global-Specialties/1420/AC-Power-Supplies/

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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Wed 14, 2018 12:31 am 
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Joined: Dec Tue 29, 2015 8:23 am
Posts: 155
Location: Australia
Monarke4 wrote:
For reference, the B&K 1655A is actually a Global Specialties 1420 and can be purchased currently $73.26 less than the B&K 1655A. I have no relationship with Global Specialties or TEquipment.

https://www.tequipment.net/Global-Specialties/1420/AC-Power-Supplies/

For the record, I think its actually the other way around - the B&K Precision 1655/1655A is the original (or, more correctly, one of their subsidiaries e.g. Itech, is the OEM), and the Cal Test / Global Specialties 1420 is the rebadge.

(Not that it matters, and for $73 less then go for the GS, but you'd be surprised how much "branded" low-mid level test gear traces back to B&K...)


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 Post subject: Re: Should I get a variac or Sencore pr570
PostPosted: Feb Wed 14, 2018 8:08 am 
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Posts: 322
Location: los angeles, california, usa
Rod FeC wrote:
Monarke4 wrote:

(Not that it matters, and for $73 less then go for the GS, but you'd be surprised how much "branded" low-mid level test gear traces back to B&K...)


I agree, in this day and age, a significant savings is most definitely work it.

Sometimes is very difficult to figure out the "cross mix" of root manufacturers for most anything.

The on going crazy eBay asking prices for a used PR57 or B&K1655 and not "really" knowing the condition until you receive it continues. It's nice once in a while to purchase new out of the box with no hassle(s).

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