ard at p850ug1.demon.co.uk
Thu Sep 23 12:49:29 CDT 2010
> On 22/09/10 20:52, Tony Duell wrote:
> > I am going to be very wary about buying an old Fluke instrument now.
> > Since they don't have spares for old models, and since they use a lot o=
> > custom parts which are not used elserwhere, if there are any problems I
> > could be in the same situation I am in now.
> Yeah, I had a bit of a re-think when I saw the service manual for my=20
> Fluke. One custom ASIC, and a bunch of passives...
Yes, I looked at the service manual for my 85 to get the part number of
the display. That one you were supposed to repair to component level, but
it's one SMD ASIC, a handful of precision resisotrs, etc, the display,
the range swtich parts, and so on. The only source for most of the parts
would be Fluke.
And of course the time you tend to need spares is when the instruemnt is
getting old. Whcih is when they no longer have them :-(
> (Agilent U1251A)
> >> =3DA3300 ish from Farnell.
> > I've looked at those on THe Agilent website. They look nice, but withou=
> > seeing one and/or a full service manual (which doesn't seem to be
> > available) I can't comment any further.
> There isn't a full service manual -- there's a "board swapping guide"=20
> which IIRC just tells you how to get the mainboard out. Their suggestion=20
> for aligning the mode switch?
I think there are instructions on calibrating it, something which I
probably don't need...
> (paraphrasing a little here, I don't have the S/M in front of me)
> "When removing the Main PCB from the unit, ensure the mode switch is set=20
> to one of the OFF positions. The switch may be difficult to re-align if=20
> this instruction is not followed."
> I went with the highly scientific method of "figure out what mode it's=20
> in now, then set the switch to that mode and put it back together again".
:-) This is one thing that Fluke got right on the 85. The mode switch
consists of a normal swich wafer soldered to the PCB. There's a plastic
splndle that goes inot that with a hexagonal socket on the top end. A
wiper assembly clips on the back (it will on;y fit one way round) to
contact the resistive tracks on the PCB to tall the ASIC what mode it
should be in. (the wafer does things like selecting current shunts IIRC).
The switch knob comes off with the top case. Now the neat part is that
there's a mounted pointer on the top of that little plastic spindle, and
legends mounlded itno the top PCB cover (which also carries the display.
So what you do is put he spindle throug hthe wafer (I can't rememebr ifit
will fit 2 ways round, if so, you have to work out which one makes sense,
then clip on the wiper (that will only fit one way. Then fit the PCB
covers/display. The pointer on the spindle now points to a legend on the
upper PCB cover. you set the user knob to the same position (say DCV) and
then put the case together.
> To my knowledge, there isn't a CLIP available for it, nor are any of the=20
> parts on the mainboard available separately, except the fuses. Those are=20
Err, no thanks. \ppounds 300 is a considerable expenditure for me, and I
expect ot be able to keep it going...
What has gone wrong with the world? Surely the sort of person who buys a
300 quid multimeter may well be an electronics engineer quite capable of
> about =A320 EACH (there are two of them). That money will get you a set o=
> four Littelfuse DMM fuses (two to use and two spares), which work fine=20
Yes, I discovereed this too...
> and meet all the specs of the Agilent parts except for breaking=20
> capacity... though I doubt I'll be measuring any 1kA circuits with a=20
> handheld DMM!
I just hope the current range probes neer get connected straight across
the mains, or if the do, then some other fuse/breaker trips first. Or
across a chargerd car battey (which could easily supply 1kA). Both of
those I do work with, of course, but it's never eeally worried me...
More information about the cctalk