[volt-nuts] Fluke 732A schematic re-drawn?

Todd Micallef tmicallef at gmail.com
Sat Jan 20 14:33:48 EST 2018


Bill,

The reason why Q14 was dropped was that there was an additional pcb added
to the reference. The A8 preheater did not exist on the older models. It
appears the heating was changed to a split design where the heaters were
divided into two groups.
The control line still goes out P2-1 but connects to A8.

One of my 732A has this board and the reference also has the higher value
thermistor reading between 4k-5k ohms.

Todd

On Sat, Jan 20, 2018 at 2:06 PM, Bill Gold <wpgold3637 at att.net> wrote:

> David:
>
>     I will be guessing that you are discussing the lack of Q14 that is
> chassis mounted on some versions of A4, driven by Q13.
>
>     I have sent you by PM a pdf of a 732A manual that I probably got from
> FLUKE.
> If you look at the schematic for A4 this one has the chassis mounted Q14
> shown and listed in the parts list for A4.
>
>     The interesting thing here is that a manual I sent you is P/N
> 645051 dated May 1983, while another manual P/N 788414 dated
> May 1986 does NOT show Q14.
> So for some reason known only to the people at FLUKE Q14 must have been
> dropped by May 1986.  Go figure.
>
>     I don't have any other manuals except those two P/Ns.  The best I can
> figure out at this time is that Q14 was dropped between A4 Rev A and A4 Rev
> D.  According to the parts list in the May 1986 manual Q13 is a 2N3906.
> The
> Ic maximum is 200 ma.  I know that the overall current draw from the
> batteries when no AC power applied is about 250ma, but I don't know how
> much
> of that is for the heaters.
>
> Bill
>
>
> ----- Original Message -----
> From: "David C. Partridge" <david.partridge at perdrix.co.uk>
> To: "'Discussion of precise voltage measurement'" <volt-nuts at febo.com>
> Sent: Friday, January 19, 2018 4:16 AM
> Subject: [volt-nuts] Fluke 732A schematic re-drawn?
>
>
> > The schematic for the A5 Reference and Oven Controller Board has to be
> one
> > of the worst schematics I've seen in a while, breaking pretty much all
> the
> > rules on making a schematic understandable.  I suspect this was done
> > deliberately.
> >
> > Has anyone ever re-drafted this (to include the A4 pass transistor
> > components) to make sense of it?
> >
> > May your volt always be stable
> > Dave
> >
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