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 Post subject: Jameco GRP-1200 isolation transformer
PostPosted: Sep Fri 24, 2021 5:24 am 
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Joined: Jun Sat 13, 2009 12:44 am
Posts: 785
Location: Calgary Alberta Canada
I just purchased this unit and thought I would share a few pics of the interior if any one else is interested in picking one up. Seems well put together, however two issues did concern me. The first was how close the transformer was to the front wiring. The sharp edge of the transformer was really digging into the outlet wiring. The second issue was the ground connection to the metal case. No serrated washer and connected with out sanding the paint as well as the nut and bolt were only finger tight.
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I did Move the transformer to the rear by one inch to clear the front wiring. Yes, I did change the center of mass to the rear but insignificantly so. I removed the paint and installed a serrated washer as well as a locking nut for the ground issues. Some pics of my fixes which were very easy to do and took maybe 15 minutes.
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My apologies if this has been covered already. I did do a search but only went so far...


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 Post subject: Re: Jameco GRP-1200 isolation transformer
PostPosted: Sep Fri 24, 2021 11:41 am 
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Joined: Oct Sun 15, 2006 12:57 pm
Posts: 7903
Location: Liberty, Missouri
Use an Ohm meter and verify that neither of the two BLADE connections are connected to ground. If so be sure to correct the problem. The secondary, output, winding should be totally isolated from ground.

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 Post subject: Re: Jameco GRP-1200 isolation transformer
PostPosted: Sep Fri 24, 2021 10:48 pm 
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Joined: Jun Sat 09, 2007 8:14 am
Posts: 5112
Location: Melbourne, Florida
Data sheet. I'd still check though.

https://www.jameco.com/Jameco/Products/ ... 214336.pdf

RRM


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 Post subject: Re: Jameco GRP-1200 isolation transformer
PostPosted: Sep Sat 25, 2021 1:02 am 
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Joined: Jun Wed 08, 2011 2:33 am
Posts: 12214
Location: Ohio 45177
Looks isolated. But there are some commercial "isolation transformers" out there with the neutral outputs connected to ground. I have a hospital grade unit and was happily thinking it was the berries until I found out it was that way and then modded it to isolate the outputs from ground and marked it as such. But it was not something I was using on radio repairs.

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 Post subject: Re: Jameco GRP-1200 isolation transformer
PostPosted: Sep Sat 25, 2021 3:16 am 
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Joined: Jun Sat 13, 2009 12:44 am
Posts: 785
Location: Calgary Alberta Canada
No connection between neutral and ground. While it is tempting to cut the ground connection to the isolated outlets to make it truly isolated, i think I will use the ungrounded blocks that ttx450cap uses. That way when i pass on and the wife disposes of all my useless stuff the isolation unit has no hidden surprises for the new owner.
Other than the issues I found it seems well put together and the price is certainly right. I do like the fact it has the outlets on the front as well...

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 Post subject: Re: Jameco GRP-1200 isolation transformer
PostPosted: Sep Sat 25, 2021 3:29 am 
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Location: SW, MI
Don't get me involved here, I use 5-20w.

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 Post subject: Re: Jameco GRP-1200 isolation transformer
PostPosted: Sep Sat 25, 2021 3:46 am 
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Joined: Jun Fri 19, 2009 6:34 pm
Posts: 11029
Location: Long Island NY
I think your modifications are sound. The transformer will likely get hot in operation and that would not be good for the wiring pressed right up against it. That could lead to deterioration of the insulation on the wires. And yes the ground lug should be connected to bare metal, preferably with a toothed washer to give it some "bite." I always leave the ground prong connected at the outlet; the need for a ground connection does not necessarily go away with isolated power. Many electronics products with filtered power inlets use ground for common mode noise rejection in any event. The ground is not used if you only plug in a two-wire cord, and no "hot chassis" AC/DC equipment should have a three wire cord installed!

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