Electronics > Repair

Fluke 332D DC Voltage Standard Restoration

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TERRA Operative:
So I got me an old Fluke 332D.
Paid 10,000yen (about US$90) all up including shipping for it, and it was listed as kind of working but intermittently doing weird things with the output, something that screamed 'dirty contacts' to me seeing as this thing is full of rotary switches.

Got it home and it fired up fine. :D a bit scratchy on the dials here and there, so I spent some time on the lower dials with the deoxit and a light scrub with the fiberglass pen on the switch contacts and deoxit fader in the two pots. Still have to tackle the voltage selector switches.

The output is a little out, but I'll have to get my hands on an 8.5 digit multimeter to really dial it in, my best multimeter is a 6.5 digit Keysight 34461A.

I've also read that the caps in these tend to go bad, so I took inventory and made a full list on the Mouser website of caps to replace.
I won't be touching the tantalums as they are dry slug axial and are very reliable and generally fine unless obviously bad (and they are uber expensive to buy these days), but I did find all the 30D series electro caps to match perfectly (with only a little increase in rated voltage here and there). All the other standard electro caps will be replaced with Vishay axial, using the high temp and lower ESR versions where possible.

Also, what should be the Y caps on the input aren't marked with any specifications, so they will be replaced with new caps of the correct rating, along with a new mains cord so it's all shiny (The brass contacts are a bit tarnished and I have a limitless supply of mains cords).

The only thing I'm a little stuck on is the main filter capacitors.
They are 125uF, 450V Sprague caps, part number 106336 and have a really funky 5 pin footprint that no other modern caps use.
I don't know if they even need to be replaced, but if I do need to, I could either solder in some standard radial caps and just bend the leads a bit to match, or make a secondary board to piggy-back the new caps on and use jumper wires to attach it to the main PCB.

Last pic is of this type of cap.
Any thoughts?

tggzzz:

--- Quote from: TERRA Operative on July 06, 2019, 11:31:18 am ---The only thing I'm a little stuck on is the main filter capacitors.
They are 125uF, 450V Sprague caps, part number 106336 and have a really funky 5 pin footprint that no other modern caps use.
I don't know if they even need to be replaced, but if I do need to, I could either solder in some standard radial caps and just bend the leads a bit to match, or make a secondary board to piggy-back the new caps on and use jumper wires to attach it to the main PCB.

Last pic is of this type of cap.
Any thoughts?

--- End quote ---

They can be awkward to remove; care is required,

The best way is to make a secondary PCB for the new caps. One technique to avoid jumper wires is to

* measure the width of the existing lugs and diameter of holes in the existing PCB
* on the secondary PCB, put two holes slightly smaller than that distance apart
* solder a bog-standard 0.1" header into the two holes, then insert the two headers into one of the PCB holes, and solder
Ensure gaps between tracks on the secondary PCB are sufficient to avoid HV breakdown!

Edwin G. Pettis:
I have the 332B and I had to go through and replace virtually all of the caps, many had leaked.  Those large Sprague caps can be replaced with newer radial caps but be aware that (at least in the B model) they used the cans as part of the interconnect circuits, you will have to put shorts in place of the cans or you will have open circuits.  Not difficult to see where to put the wire shorts in on the PCB.  No modifications to the PCB were needed.

TERRA Operative:
Yeah I thought that might be a thing to watch for, but I just took a look and it seems like I'm safe, they aren't using the case of the cap as an interconnect on this one.

One thing I'll have to figure out is how I'll fix an adapter board in place so it doesn't stress the PCB etc.
I think I'll have to squint at it intently for a bit and maybe frown a little too until I come up with an idea.

The problem is, it's so clean inside that I want to try to keep it looking as untouched as possible. :)


Maayybbeee I could restuff those caps, but maybe I can't be bothered..... hmmm.

bitseeker:
Yeah, apart from the bit of corrosion on the controls, it's immaculate inside. Nice find, TO. :-+

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