VTVM probe modification

[Ron]

I have received a couple of requests for details of
the probe mod discussed recently in this email list.
Here it is (but do keep in mind the pros and cons).
The following pertains directly to the IM-11, IM-18'
IM-13, and IM28, but applies (possibly, with slight
changes) to most (all?) Heathkit (and similar) VTVM
models.

1. Locate the wire going from the probe phone jack
    'tip' to function switch lug A5. Disconnect wire
    from the switch.
2. Locate the wire going from function switch lug A5
    (just disconnected from) to lug A3 on same wafer
    of switch. Remove that wire and discard.
3. Connect a 1 Megohm, 1/2W (I'd use 2%) resistor
    from lug 5 (S) to lug 3 (NS) identified earlier.
4. Connect the free end of the wire disconnected in step
    (1) to lug 3 (S). You may have to lengthen it.
5. You may now use a straight through probe for both
    DC and AC/Ohms measurements. The resistor will be
    switched into the circuit in the DC positions of
    the function switch.

I'll be happy to email drawings to anyone that wants
them.

-- Ron

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