Author Topic: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown  (Read 19240 times)

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Offline krivx

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #25 on: September 08, 2015, 08:12:34 am »
Since it works so well and there's no repair video needed, maybe you could do a video about cleaning yellowed plastic enclosures.

http://www.retr0bright.com/

Unfortunately, this is only a temporary "fix". The yellowing eventually returns, even if the plastic isn't exposed to light.

Retr0Bright (or RetroBright) treated plastics re-yellowing even with minimal light exposure?

Apparently there have been good results with using a UV-protective clear coat immediately after the Retr0Bright.
 

Offline Dave

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #26 on: September 08, 2015, 11:30:36 am »
You completely derped your error calculations.
9.9974mA with a 10mA reference means it's 0.026% off, not 0.26%.  It's well within the 0.05% + 5 counts spec.
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Offline German_EE

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #27 on: September 08, 2015, 07:29:07 pm »
There is a type of elevator that I used to service that has a VFD display for the floor indicator, a common complaint from customers was that the display was too dim. Our solution was easy, strip the display down and clean the inside of the smoked plastic cover, a design error meant that it got coated with a film of oil and then a layer of dust.

Try it with a Fluke 45.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

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Offline Tothwolf

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #28 on: September 08, 2015, 08:41:18 pm »
Unfortunately, this is only a temporary "fix". The yellowing eventually returns, even if the plastic isn't exposed to light.

Retr0Bright (or RetroBright) treated plastics re-yellowing even with minimal light exposure?

Apparently there have been good results with using a UV-protective clear coat immediately after the Retr0Bright.

Nope. Treated plastic re-yellows even when stored in a dark closet. Note the photos in the link I posted are followup photos to those in the original "Retr0Bright" link.

UV / light are not the reason the plastic returns to a yellow color, so a clear coat will not stop the chemical reaction. There are more free bromides below the surface layer, and a peroxide treatment can only work on the outermost surface of the plastic. Multiple re-treatments might eventually slow down the re-yellowing process (although that also risks damaging the plastic), but even that won't stop it completely. A clear coat over the plastic would actually be worse than no coating because once the plastic had been coated, you could no longer re-treat the plastic.

http://www.vintage-computer.com/vcforum/showthread.php?35227-Retr0Bright-Does-re-yellowing-occur-even-in-the-absence-of-UV-light&p=359591#post359591

"Retr0Bright" in its current form is only temporary, and in many cases, probably isn't worth the trouble since the results are not long lasting or permanent.
« Last Edit: September 08, 2015, 08:48:19 pm by Tothwolf »
 

Offline krivx

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #29 on: September 08, 2015, 09:11:05 pm »
Unfortunately, this is only a temporary "fix". The yellowing eventually returns, even if the plastic isn't exposed to light.

Retr0Bright (or RetroBright) treated plastics re-yellowing even with minimal light exposure?

Apparently there have been good results with using a UV-protective clear coat immediately after the Retr0Bright.

Nope. Treated plastic re-yellows even when stored in a dark closet. Note the photos in the link I posted are followup photos to those in the original "Retr0Bright" link.

UV / light are not the reason the plastic returns to a yellow color, so a clear coat will not stop the chemical reaction. There are more free bromides below the surface layer, and a peroxide treatment can only work on the outermost surface of the plastic. Multiple re-treatments might eventually slow down the re-yellowing process (although that also risks damaging the plastic), but even that won't stop it completely. A clear coat over the plastic would actually be worse than no coating because once the plastic had been coated, you could no longer re-treat the plastic.

http://www.vintage-computer.com/vcforum/showthread.php?35227-Retr0Bright-Does-re-yellowing-occur-even-in-the-absence-of-UV-light&p=359591#post359591

"Retr0Bright" in its current form is only temporary, and in many cases, probably isn't worth the trouble since the results are not long lasting or permanent.

IIRC the theory of clear coat was to not to just to prevent UV damage but also oxidation. I can't remember where I saw this though, sorry.
 

Offline Macbeth

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #30 on: September 08, 2015, 09:24:42 pm »
"Retr0Bright" in its current form is only temporary, and in many cases, probably isn't worth the trouble since the results are not long lasting or permanent.
I disagree. It seems the discoloration comes back after YEARS. So really, pretty much just like the original equipment!

I can't think of a better way of restoring something than to then have its real genuine crap-factor to be restored too! as a purist surely this is better than an artificial cover-up?

I have to admit some of my PC PS/2 keyboards are in a sorry state and I tend to strip them down and give them a good scrub every few years, adding the Retr0bright treatment doesn't look like much bother.
 

Offline linux-works

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #31 on: September 08, 2015, 09:24:57 pm »
question to the plastics engineers out there: is it just a matter of cost, at manufacturing time, that could avoid the ugly yellowing, or was it that they simply did not have the ability to make plastic stable that long and not change color?

is it just about economics?  something tells me it was always the vendor's choice in how long they wanted the color to remain 'clean' and new looking.

admittedly, how many things are designed to 'look good' over decades?  if its commercial, who cares what it looks like; and if its commercial it will be expensed over time and rarely do you carry old equipment on the books for decades (does anyone, ever?)

so its only us collectors who would care; and I bet its not worth any money to the vendors to make the plastics last any longer than they currently do.  shame, of course.  but I assume its all about money and not due to it being particularly 'hard'.

Offline Muttley Snickers

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #32 on: September 08, 2015, 10:24:51 pm »
If it's any help I have a couple of function generators that are severely affected that came from a university and these were the two best out of all of the ones that they were getting rid of in regards to the discolouration. the underside of the units are pretty much unaffected and they show clear "bra lines" on the top where the handles had been left in situ for who knows how long.

The university electronics department had large surrounding windows so I would assume that depending on where particular units had been located dictated how severe the sun tan effect became. My intention was to dismantle them and use some cutting compound and then a light buff with a polishing wheel just to skim off a bit of the textured surface, I am more than happy to use these as guinea pigs if anyone has some suggestions that we could try otherwise they may just get a new coat of plastic paint unless I can find new cases, these will eventually be given away to a more needy person but I feel it is my duty to make them the best that they can be.

Competition: guess which one a was geek and enjoyed looking out the window.

Note: please do not quote this post as it may be considered as off topic and I might relocate it to another thread if I can find a suitable one.




« Last Edit: September 09, 2015, 09:06:49 am by Muttley Snickers »
 

Offline Tothwolf

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #33 on: September 09, 2015, 02:13:50 am »
question to the plastics engineers out there: is it just a matter of cost, at manufacturing time, that could avoid the ugly yellowing, or was it that they simply did not have the ability to make plastic stable that long and not change color?

is it just about economics?  something tells me it was always the vendor's choice in how long they wanted the color to remain 'clean' and new looking.

admittedly, how many things are designed to 'look good' over decades?  if its commercial, who cares what it looks like; and if its commercial it will be expensed over time and rarely do you carry old equipment on the books for decades (does anyone, ever?)

so its only us collectors who would care; and I bet its not worth any money to the vendors to make the plastics last any longer than they currently do.  shame, of course.  but I assume its all about money and not due to it being particularly 'hard'.

It wasn't about making the plastic stable. These bromine compounds were added to plastics as flame retardants.

I suspect earlier on no one realized what these bromine compounds would do long term. Later, bean counters probably didn't care if they turned plastics yellow/brown. Due to their toxicity and that they are now classified as cancerigans, many of these compounds have been phased out, so newer plastics might not be affected by this today.

Edit -- another link which explains the degradation process: http://deskthority.net/keyboards-f2/retrobrite-the-yellow-strikes-back-t6084-60.html#p228424
« Last Edit: September 09, 2015, 05:50:13 am by Tothwolf »
 

Offline Treehouseman

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #34 on: September 10, 2015, 01:34:33 am »
Got a chance to quickly tear down one of my 45's to show some differences, namely the addition of a 440mA HRC fuse for the 100mA range. Tried to take a look around for a solid date code, the relays are saying 0884, but the asic is saying 4201. The latter seems more reasonable to me because of the fact mine still has a bright screen and no yellowing, but that seems awfully recent. These were "defective" from the local community college, I nabbed 3 of them, all had blown 440mA fuses because no one could be bothered to look inside the thing past the 500mA fuse in the jack itself.

I can't upload all the photos in this post due to size, but they're here in my dropbox https://www.dropbox.com/sh/d2uza7q90yfm3m7/AAC7xDoRl8RfCbU43NXhKk84a?dl=0
 

Offline nicknails

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #35 on: September 10, 2015, 12:29:36 pm »
Dave mentioned the electrostatic shield that's between the primary and the secondary. I'm wondering what this is and where I can find some? I'm assuming it's some sort of foil and there's different versions for frequencies, etc, etc. I did a quick search on Digikey and Mouser and couldn't find anything. Is it called something else?

P.S. The company I work for has 42 Fluke 45s!
 

Offline bigsky

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #36 on: September 11, 2015, 10:11:56 pm »
I really enjoyed this video - it shows the superb quality of a Fluke meter - 22 years old, still working and in spec. I wonder if today's products will last as long.
 

Offline linux-works

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #37 on: September 11, 2015, 10:49:37 pm »
is there a way to run the 45 with the display off and only doing i/o over the serial or gpib ports?

I thought there was either a front panel seq or a scpi cmd to turn the display off, but I'm not seeing it.

Offline Stephan_T

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Re: EEVblog #791 - Ebay Fluke 45 Multimeter Teardown
« Reply #38 on: September 16, 2015, 04:16:03 pm »
Hi Dave,

regarding your isolation transformer and its electrostatic shielding you claim that this "basically cuts its capacitance completely down to zero". Well I challenge you on that one.

My experience is: "Nothing isolated has a capacitance of zero". Parasitic capacitance is every where :-)
I have a very similar isolation transformer (HP M1389A), which also has this kind of shielding (protective earth wire going into the toroidal transformer).
When i run it at 230V, the output voltages of the secondary contact measured with the 10M? DMM show 160V (at one side, 67V on the other). As far as i know, the VDE 0701/0702 (similar to PAT, portable appliance testing) specifies a 2k? resistor to ground for testing touch currents on the isolated parts of a device. These 2k? represent the internal resistance of the human body. The current limit is specified at 0.5mA.

The 160V @ 10M? drop down to about 200mV when grounded with 2,2k?.
0.2V/2200? = 91µA

230V / 91µA gives about 2.5M? impedance  (@50Hz).

With Xc = 1/(2*pi*50*C) I get an effective capacitance of about 1.27nF or 1270pF.
Close, but not quite zero ;-)
Measuring capacitance between secondary and ground also gives me a value of 1,15nF (all measurements done with a Brymen BM257)

BTW, have you seen this thread (replies #4ff) about isolation transformers? I was shocked to see that there seem to be pseudo isolation transformers, which have a direct ground connection on the secondary side of the transformer. Such devices should not be called isolation transformers.
 


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