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" <[email protected]> To: "Discussion of precise voltage measurement" <[email protected]> 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 <[email protected]> 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" <[email protected]> > > To: "'Discussion of precise voltage measurement'" <[email protected]> > > 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 > > > > > > _______________________________________________ > > > volt-nuts mailing list -- [email protected] > > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > > > and follow the instructions there. > > > > _______________________________________________ > > volt-nuts mailing list -- [email protected] > > To unsubscribe, go to https://www.febo.com/cgi-bin/ > > mailman/listinfo/volt-nuts > > and follow the instructions there. > > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
