Fluke SL935 Resistance Standard project (rare prototype teardown included)

[ap]

732B external battery charger?

[tszaboo]

So it is 3 digit, black
not a 732B
not a 731B
not a 734A because wrong shape and even you are reasonable.
not a 792A because you already have one.
and battery powered, so probably not their shunt resistor.

Must be the battery pack for a 792A.

[doktor pyta]

So simple.
Transfer switch for 792A.

[Jeroen3]

You are liking this aren't you? 

[TiN]

NANDBlog, doktor pyta
Sorry folks, it's nothing related to 792A, that would be too easy guess

ap

732B external battery charger?

This one is on Fedex now, delivery target next Tuesday 

[SvanGool]

- It is 3 digit, black
- Not a 732B
- Not a 731B
- Not a 734A because wrong shape and even you are reasonable.
- Not a 792A because you already have one.
- Battery powered, so probably not their shunt resistor.

- Many would surely want this
- It's made by Fluke
- Uses something from Fluke 732B, but it is no 732B
- Something with a battery, and supposed to be powered all the time.
- Parts used came right from some serious gray beard-designed gear.
- 792AIs about twice as large than this, even without battery block.
- It's 30% of 732B
- It's only 30% of the package on the photo

1 The heater of a 732B: an Alox (aluminum-oxide) substrate based power resistor ?
or
2 The front panel of a 732B?

 

[Vgkid]

Was it the prototype precurser to the 732. I saw a teardown on the volt-nuts mailing list/bbs-38.

[mimmus78]

Two pages and still no reply.

This is a torture.

 

[ZeTeX]

SL935

[CalMachine]

SL935

Tell the man what he has won!

[Macbeth]

Well, maybe it's 30% of 732B, but anyhow it doesn't have this model number.

This must be the world famous Fluke 219.6B, surely?

[TiN]

ZeTeX wins a thank you All my money budget depleted to thank any more  .



It's only oven assembly with resistor standard guts inside and refaced 732B front panel.
That's why I bought 7001 battery block, which is essentially everything else. So I can plonk this prototype inside, hook it up to oven and get it nice and stable.
Maybe I can find a spot for KX LTZ reference inside the oven, so I can get 10V out of it too. That would be perfect 5700A calibration travel standard 

At least that's how I comfort myself doing such purchases.

[Vgkid]

Woah, I'm really looking forward to this one.

[Jeroen3]

S/N 001 ?

[CalMachine]

ZeTeX wins a thank you All my money budget depleted to thank any more  .



It's only oven assembly with resistor standard guts inside and refaced 732B front panel.
That's why I bought 7001 battery block, which is essentially everything else. So I can plonk this prototype inside, hook it up to oven and get it nice and stable.
Maybe I can find a spot for KX LTZ reference inside the oven, so I can get 10V out of it too. That would be perfect 5700A calibration travel standard 

At least that's how I comfort myself doing such purchases.

She's a beauty!!       I am interested in what its values are   

[tszaboo]

Let me get this straigt. It is a resistance standard, with battery backup and heater. That sounds just bad. Although, I understand you have all the tools to calibrate 3458As now.

[EEVblog]

S/N 001 ?

Yeah, 

[TiN]

I don't know any history or previous owner of this unit but my best guess of this was something like this:

One of Fluke standards/metrology lab managers got tired of hauling SR104s and packs of oily Fluke 742A/Thomas resistors around to calibrate 5700A/5720A, gather a team and said :
- M: Hey guys, we have those nice 732B's, which are real bobby dazzlers, how about we take one 732B and butcher it up to convert into resistor standard
- Somebody from calibrator repair line: Hmm, I can donate stash of dead ohm boards from 5700A's for this fun
- Somebody from assembly line: sounds like a one shift break job to me..
- Somebody from ID team: I can stick some black tape and add some funny looking silkscreen, no worries.
- Accounting: Hey wait, what I do for missing parts in database?
- M: Just put it under some unused model number, let's do it! Call it 744A...
- DBA: mm,, 744 already used for calibrator...
- M: Whatever, call it Standards Lab 935 then! I need this thing tomorrow to calibrate that stash of 5700As!
...week after...
- Here's the box, we made it for 1 ohm and 10Kohm, stable enough to transfer resistances for 5700A cal. So it's a perfect match for 5700A.
...year after...
- New accounting hire: What is this SL935 thing? We don't sell this product, what to do with it?
- Just toss it into reject bin, I don't know what that is.
... some time after ...
Box travels around swapping owners, till finally ends up in my greedy hands 

My best guess  . If somebody from Fluke reads this, and actually knows, I'd love to hear.
Oven and resistors might sound bad, but it may not be that simple. For calibration or transfer purposes it might be better to have larger but known drift of resistance, instead of varying output due to tempco. Oven can be set low enough, to be just over the ambient. I don't know how hot 732B ovens usually run (yet).

[HighVoltage]

And how should we ever have guessed this one? 
And how exactly did this one end up in your hands?

Amazing!
Can not wait for tear down pictures.

[ManateeMafia]

At least I know how I came across that lone reference oven on ebay. Some sacrifices must be made. 

[TiN]

Many sacrifices are required. That's the way it works.

HighVoltage
I paid in gold for it, it wasn't easy, but my grip was firm. I was hunting down the 5700A transformer assembly, and after deal was already done, guy sending a photo of this thing asking "maybe I want this too?". Hell yes, I want, especially after seeing what's inside. 

[ManateeMafia]

It's almost believable but I don't think you could ever come across a stash of dead 5700A boards. 

[TiN]

That's one mean joke... I hold EEVBlog responsible! Chassis under bag unfortunaly not Fluke's, that's semiassembled 8753A VNA, which just sits there for almost a year already. Have nice thick layer of dust on it.

[CalMachine]

 

[Vgkid]

I'm looking forward to this.
Heck I have an ovenized resistance reference. Ok it is not overly accurate, resistors are not low TC(2 are Vishay hermetic power resistors, Why they could use more precise resistors + external trim network  )
left box