Keithley 179 TRMS DMM Repair/Refurb

[xrunner]

I'd recommend "Displex" for the panel. It's made to remove scratches on mobile phone screens, but it's great for restoring plexiglas surfaces. You can pick it up on ebay: http://www.ebay.com/itm/Displex-Scratch-Remover-Display-Polish-Cleaning-Cloth-For-Clear-Plastic-Screens-/310851033895?pt=LH_DefaultDomain_0&hash=item48602a5b27
I've restored quite a few things with this and it gives great results.

Bryce.

Interesting, I'll order some. 

[xrunner]

Input terminals cleaned up and re-installed.

Next on stage - MEK (methyl ethyl ketone) meets plastic. 

[xrunner]

It appears that the case was indeed dropped at one time. The handle is cracked as well as parts of the case. No problem, as the plastic welder I use (MEK) will make short work of it. Simply open the crack a bit and apply the welder, and then press together. Apply some pressure for a few hours and presto - good as new.

Upcoming events news: Got two more vintage meters coming - Fluke 8600A and an HP 3476A. 

[SeanB]

Lucky I have MEK in an ultra pure form, thanks to Linx printers that use it as a solvent for the ink. Really pure, in a lovely 500ml PET bottle that is nice to use aside from the lids that disintegrate. The solvent migrates through the PET and the sealed on foil top cover with time. They even have an expiry date on them, though you definitely want to store them cool, otherwise it will evaporate right through the sealed bottles. Lovely printer, never uses ink ( or at least never uses more than 300ml between service cycles when you dump the whole 1.5l ink reservoir) but simply makes up using the MEK solvent. It will print on a raw egg.

[ivan747]

Do not use the gasoline. Use citronella oil ( or just use a lemon skin and rub it on the label till it is damp with the oil off the skin) and leave for a minute or two for the adhesive to soften. Pretty much any citrus fruit, like lemon, grapefruit or Navel oranges will do, as they all have citronella oil in the sin surface. Just rub the skin outer while squeezing it firmly to release the oil.

Thanks for clearing that up. I wasn't gonna get gasoline out of my car just for that anyway, that's way too much hassle (potentially danger) when I can use a fruit.

[xrunner]

All the repairs are done. The plastic parts look good and are strong. I washed it all in warm soapy water and will apply a coat of Armour All. The bottom is missing a rubber foot, so I will just replace them all with some I have on hand so they will all look the same.

[ivan747]

I'd recommend "Displex" for the panel. It's made to remove scratches on mobile phone screens, but it's great for restoring plexiglas surfaces. You can pick it up on ebay: http://www.ebay.com/itm/Displex-Scratch-Remover-Display-Polish-Cleaning-Cloth-For-Clear-Plastic-Screens-/310851033895?pt=LH_DefaultDomain_0&hash=item48602a5b27
I've restored quite a few things with this and it gives great results.

Bryce.

I'll go to the place where glasses are sold (I don't know how that's called in english) and see if I can get a product made to clean plastic lenses on sunglasses or something like that. Or maybe a product that cleans plastic car headlights.

[ivan747]

Did the bottom sticker remained intact even with the warm water and soap wash?

[xrunner]

Did the bottom sticker remained intact even with the warm water and soap wash?

Yes it did, but I didn't wash it very hard. Boy the old case really looks good now! 

I put it together just to see what it looked like, but now it's apart again because I'm going to go through the cal procedure. Stay tuned! 

[xrunner]

Going to go through the cal today. It's nice that it has the cal points and steps are printed right on the top of the shield. All the steps are numbered for you.

Also fixed up the bottom feet with new rubber. And it came missing one case screw. I had one that was too long in my junk box so I cut it down to the correct length.

[xrunner]

Cal worked out well - looks like I'm done with this one. Will post final pics tomorrow.

Here's what I'm currently bidding on - all "not working". I'd prefer "not working" to some flaky problem, it's easier to fix (unless the entire inside is a charcoal brick).

[ivan747]

Good way to fill up emplty bench space, huh?  O0

[xrunner]

Good way to fill up emplty bench space, huh?  O0

LOL - yea but I'm quickly running out of bench space. I might have to rationalize a total redo of my lab area. 

[VK5RC]

Did you find any tricks to get the MEK in the right spot and not others? Did you use a brush or something?
Thanks Rob

[xrunner]

Did you find any tricks to get the MEK in the right spot and not others? Did you use a brush or something?
Thanks Rob

The bottle I have it in has a brush. Just paint it on the pieces. It will ruin the finish of any plastic it touches so watch for that.

[xrunner]

Calibration done -

[xrunner]

Project done! Looks good and fully functional.

Going back - this is what I got in the mail - broken case parts and not working -

[ivan747]

It even looks shiny! 

[McBryce]

Excellent work xrunner, that's one you can be proud of.

McBryce.

[xrunner]

Thanks guys! It just shows what you can do with something that somebody else doesn't want to fix. One man's trash is another man's treasure, as they say. I hope by posting these restorations it will help someone else in the future.

Just got another used DMM one in the mail.  Look for a new project w/pics tomorrow on this same board.

[Vgkid]

Good job

[Shock]

Xrunner question on how you used the "MEK", I can purchase it 100% pure does just MEK by itself weld?

According to the MSDS for PLASTRUCT PLASTIC WELD CEMENT
Methylene Chloride*# (Dichloromethane)  80-90%
Methyl Ethyl Ketone (MEK) 5-15%

[PedroDaGr8]

Xrunner question on how you used the "MEK", I can purchase it 100% pure does just MEK by itself weld?

According to the MSDS for PLASTRUCT PLASTIC WELD CEMENT
Methylene Chloride*# (Dichloromethane)  80-90%
Methyl Ethyl Ketone (MEK) 5-15%

I've used CHCl₃ (Chloroform) and CH₂Cl₂(Methylene Chloride) to plastic weld LOADS of plastics before. I have never tried using MEK though I have some in the lab. I'm not sure if the MEK works on different plastics than Chloroform but the Chloroform/Methylene Chloride works wonders. I have repaired broken parts on instruments before that were basically as strong as new. One piece in particular, was a stop on an instrument door. Someone slammed open the door on an instrument and broke the stop. Plastic weld it back in place, it hasn't broken off again in three years of daily use.


Just found a convenient list:

Plastics that both will do:

• Polymethyl methacrylate (Acrylic)
• Cellulose acetate butyrate (Butyrate)
• Low density polyethylene (LDPE)
• Polycarbonate
• Copolyester (Polyethylene terephthalate glycol - PETG)
• Polystyrene
• Polyvinyl chloride (PVC)

Plastics that only CHCl3/CH2Cl2 will do:

• Cross-linked low density polyethylene (PEX)
• Ultra high molecular weight polyethylene (UHMW)
• Polyester (Polyethylene terephthalate - PET)
• Polypropylene

Plastics that only MEK will do:

• Acrylonitrile butadiene styrene (ABS)
• Polyacetal (Delrin - POM)
• High density polyethylene (HDPE)

Plastics that NOTHING will weld:

• Nylon
• Teflon

Looks like I need to take home some MEK.

[Shock]

Have you got a source for that info? While looking I found this:

http://www.plasticsintl.com/plastics_chemical_resistence_chart.html

[rrinker]

 Plastruct actually sells multiple plastic weld products, as they make structural plastic pieces in both ABS and Styrene. MEK by itself does a nice job of welding styrene plastic - as a model railroader I do a lot of plastic assembly, mostly with styrene, and while there are various cements that are partly MEK combined with other solvents, they are often relatively expensive per volume relative to going to the hardware store and picking up a pint container of MEK.