MA-18-1(?)

[Jack Crenshaw]

There's a place called Antique Electronics which might have what you need.  During the
transition from tubes to transistors, a few companies made plug-replaceable units, i.e.,
transistors that mimicked their tube counterparts, in 7- or 9-pin packages.  I do believe
that they included the 12AT7 and other tubes used in Heathkit's VTVM's.  I recall seeing
them in a catalog, and not too expensive, either -- no more than the current prices of
tubes, for sure!

Sorry, I don't have the URL, and not positive on the name, but it's a lead.

Jack

Chuck Penson wrote:

> Got this message from a fellow looking for details on the solid state
> replacements for the tubes in Heath VTVMs.  If anyone can help him out
> please respond directly to him.
>
> Many thanks!
>
> Chuck / WA7ZZE
>
> --------- Begin forwarded message ----------
> From: "John H. Gibson" <gibson at alma.edu>
>
> I remember when Heath sold solid-state replacements for the vacuum tubes
> in their VTVMs. I believe the part number was IMA-18-1(?), but I do know
> that
> these solid-state replacements appeared at the same time that the IM-18
> VTVM came on to the market.
>
> I have several old Heathkit VTVMs and would like to install solid state
> replacements for the tubes in at least a couple of them. Do you know what
> was inside
> the two components of the IMA-18-1? I assume a pair of FETs for the 12AU7
> replacement, and a pair of diodes for the 6AL5 replacement, but I would
> like details.
>
> One other question: Have you seen a good circuit for a battery
> replacement for the VTVM? I assume I can do something with a 317 voltage
> regulator, but I am
> curious to know what others have done.
>
> Merry Christmas and 73
> John Gibson
> Office phone: (517) 463-7187
> Secretary: (517) 463-7198
> Office FAX: (517) 463-7076
> Home phone: (517) 463-3632
> e-mail: gibson at alma.edu
>
> --------- End forwarded message ----------
>
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