VTVM Mod

[Deane D McIntyre]

>  Seems to me I remember a Heath mod kit for their VTVMs which allowed
> for a "solid state" plug-in to be used in place of the 2 Tubes in
> their meters.  Anybody remember that?   es 73 Ray
> --

This was the Vacuum-Tube Voltmeter Modification Kit Model IMA-18-1

This kit consisted of solid state plugins (don't know what was
inside them) for the two tubes:

TR1002SS Diode, part No. 150-57, to replace the 6AL5
TR1119SS Triode, part No. 150-58, to replace the 12AU7

as well as a 10 megohm resistor, part No. 1-40, to replace the 22 megohm
resistor in the 6AL5 circuit.

The ENTIRE Step-By-Step Instructions for this kit were:

( ) Unplug your VTVM from the AC Outlet
( ) Refer to your Manual's "Final Assembly" steps and remove the back
    cover or remove the instrument from its cabinet
( ) Use the partial schematic below and locate the 22Mohm (red-red-blue)
    resistor at location "A". Remove this 22 Mohm resistor and replace it
    with the 10 Mohm (brown-blacl-blue) resistor supplied with this
    Modification kit.
( ) Your VTVM may or may not have a 22Mohm (red-red-blue)
    resistor at location "B". If your VTVM does have this resistor, cut it
    out and discard it. Do not replace this resistor.
( ) Remove the 6AL5 and 12AU7 vacuum tubes from their sockets
( ) Install the TR1002 SS diode (#150-57) in the 6AL5, 7 pin tube socket
( ) Install the TR1119 SS diode (#150-58) in the 12AU7, 9 pin tube socket


The two 22 Meg resistors were both connected to pin 7 of the 6AL5; the
one going to ground ("B") was removed, the other ("A") was replaced
with the 10 Meg.

I don't have the kit, just the manual copy (all two pages of it!)

I presume the TR1009 was just a pair of diodes; what was in the TR1119
I wonder?

73, Deane D McIntyre VE6BPO
dmcintyr at acs.ucalgary.ca

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