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

[Bill Gold]

All is now explained.  I just never considered all of this before, nor has
it ever come up.  This should help David understand what is happening in his
732A.  His is a later model obviously.  I will have to examine all of my
instruments next time the opportunity presents itself.

Thanks,

Bill

----- Original Message ----- 
From: "Todd Micallef" <tmicallef at gmail.com>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Saturday, January 20, 2018 11:33 AM
Subject: Re: [volt-nuts] Fluke 732A schematic re-drawn?


> 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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