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Need info on RCA Isolation Transformer

Discussion in 'Electronic Basics' started by NeoVolt, Jul 30, 2003.

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  1. NeoVolt

    NeoVolt Guest

    I got an RCA Isotap II at the flea market on sunday.
    I thought,"Wow, cool, a cheap form of variac!" and talked
    the guy down to $4 from $20.

    I can see that the original power cord was replaced at some
    point. The guy selling it had no idea what it was or most of
    the other equipment he had for that matter. He had a couple
    old HP power supplies, an HP Frequency counter with Nixies
    and original manual, some Sencore test equip and various other
    goodies. I got the HP Freq Counter for $8 and had a friend
    test it for me, it works great! One PSU was almost totally burned
    up inside but the other I got for $9. It works great too!

    The RCA Isotap has 2 switches a 2 prong plug socket and 2
    small round sockets labeled "Monitor", possibly for meter test
    leads. The first switch has 6 positions marked SEC OFF, 25,
    50, 75, 100 and 125 for voltage. The second switch has
    voltage markings of 0, 5, 10, 15, 20, 25 and that voltage is
    added to the voltage from the first switch.

    There is a schematic diagram of the circuit on the back of the
    unit but some of it is worn off. The problem is that I assumed
    ( I know it makes an ass out of me) turning switch one to OFF
    would prevent any power to the plug socket or the "Monitor"
    sockets but instead I measure a voltage of 75VAC from both the
    plug socket and Monitor sockets..

    I'm wondering if any mistakes were made in replacing the power
    cord or if a winding is shorted somewhere.

    Could anyone help me out with this? I can not find any
    documentation for this thing anywhere.

  2. Uns Lider

    Uns Lider Guest

    Have you tried it with a night-light plugged into the socket? Maybe it's
    just picking up a few nanoamps from the air... Or maybe someone messed
    with the switch.

    -- uns
  3. NeoVolt

    NeoVolt Guest

    Just tried it out with a couple NE1's and there's power there.
    I guess I'll have to open 'er up.

  4. Guest

    Don't trust the neons. Plug a 100 watt lamp into it, then
    measure the voltage. The neon's have a 100k series resistor,
    so they draw very little current. 4 bucks for that is a
    really good deal for you!
  5. NeoVolt

    NeoVolt Guest

    Yep the 100watt lamp did the trick! Thanks for reminding me
    about using the lamps.
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