EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: xrunner on February 28, 2015, 06:49:28 pm
-
Here we go again ...
Glutton for punishment I know, but here we have a Keithley 179 TRMS DMM gotten off Ebay. It has cosmetic issues of course, such as broken pieces of plastic and a peeling front overlay, but it also has an electronic problem of some sort.
The issue is that the display has random variations of intensity and glitches and little fits. I took a pic of it but it doesn't really show the variations you would see in real time. I also hear a faint buzzing in the back that sortof comes and goes. Anyway, let's see where we go with this baby. Be back later with more info. 8)
(https://lh5.googleusercontent.com/-CiICXMGDNqQ/VPIDtsNNj2I/AAAAAAAABsU/N-hgwvkzvOc/w1024-h768-no/IMG_0650.png)
(https://lh6.googleusercontent.com/-8RFAUvPnsGY/VPIFTOBOFBI/AAAAAAAABss/YR0z1MCGC_U/w1024-h768-no/IMG_0654.png)
(https://lh3.googleusercontent.com/-rlYbFZzbV24/VPIDtkcTHXI/AAAAAAAABsI/eV6PNDCTXSg/w1024-h768-no/IMG_0652.png)
-
Obviously someone's been in this before. I don't like that because it's not a virgin repair, there's no telling what's been mucked with. As in the last meter I worked on, it looks like the +5V rail has problems. What's with all the meters I get having +5V issues? :-//
But I'll press on. I love the wires going to the front test lead jacks. :palm:
(https://lh4.googleusercontent.com/-RzhscqsdzaA/VPJQEBKmZDI/AAAAAAAABtc/8AD-l0uf_Fk/w1024-h768-no/IMG_0655.png)
(https://lh4.googleusercontent.com/-AVKK463Eo54/VPIDuEnK4_I/AAAAAAAABsQ/VPcXDsVXCb8/w1024-h768-no/IMG_0651.png)
(https://lh5.googleusercontent.com/-qGUh0RFJn6A/VPIDukr2lCI/AAAAAAAABsY/wUo_1lsNnQo/w768-h576-no/IMG_0653.png)
-
I had the exact same problem with the digits on my Keithley 191. It was a cracked solder joint on the transformer, which is soldered directly to the PCB, which can explain why it cracked in the first place. Try that first.
I'd also clean that flux off and take it to a cal lab if budget allows. Screw that, I would resolder the parts completely. Someone messed with the low leakage circuitry. Let's hope they didn't mess with binned parts or matched pairs or anything like that. ***Is that metal can the voltage reference???!!!*** :-[ Go download the schematic off keythley.com while you can. You will have to leave your email address but it's okay, they don't spam. Try to figure out what was botched/repaired.
Subscribed.
P.S. if you're going to restore the plastics, do tell us. I'm interested.
-
Good luck. That 4 wire resistor/relay(beside the switches, furthest from viewer ) doesn't look very good.
-
Good luck. That 4 wire resistor/relay(beside the switches, furthest from viewer ) doesn't look very good.
That must be the current shunt. Not critical unless you care about it.
-
I have one winging it's way across the Atlantic to me. Saving 5l of pure methanol for cleaning the board in places ( not the switches) and then will see how it behaves. Has the battery removed by now, to cut the shipping mass.
-
Looks like a bit of a challenge, good hunting!
Thanks for sharing your work.
-
I had the exact same problem with the digits on my Keithley 191. It was a cracked solder joint on the transformer, which is soldered directly to the PCB, which can explain why it cracked in the first place. Try that first.
I'd also clean that flux off and take it to a cal lab if budget allows. Screw that, I would resolder the parts completely. Someone messed with the low leakage circuitry. Let's hope they didn't mess with binned parts or matched pairs or anything like that. ***Is that metal can the voltage reference???!!!*** :-[ Go download the schematic off keythley.com while you can. You will have to leave your email address but it's okay, they don't spam. Try to figure out what was botched/repaired.
I got the schematic off the internet when I bought it, so I'd have it ready. If you go by the solder flux residue, it looks like what was replaced was a small bridge rectifier, a low power 15V regulator, and some signal conditioning components in the attenuator section.
P.S. if you're going to restore the plastics, do tell us. I'm interested.
Will do. I will have to re-attach plastic parts and repair others, and general clean-up.
Good luck. That 4 wire resistor/relay(beside the switches, furthest from viewer ) doesn't look very good.
It doesn't look good but that's just the way it's made. I thought the same thing but it just has a case that looks bad, it has not been damaged.
I have one winging it's way across the Atlantic to me. Saving 5l of pure methanol for cleaning the board in places ( not the switches) and then will see how it behaves. Has the battery removed by now, to cut the shipping mass.
Yea mine needed cleaning too. I need to get some methanol.
Looks like a bit of a challenge, good hunting!
Thanks for sharing your work.
Thanks, I'll post more today as I investigate things.
In the meantime I need to repair the front panel, because the overlay has been mucked up by being re-assembled improperly. Some of the edges are curled up pretty badly. What I'm doing now is not gluing it but trying to impart a flat "memory" to the mucked up plastic overlay. I want the plastic to lay flat by itself before I glue it down, so it won't try yo pull off later. :)
(https://lh3.googleusercontent.com/-h2SEPAdIX1g/VPJQOoqUqwI/AAAAAAAABtk/ZMyTR14v7N0/w768-h576-no/IMG_0657.png)
-
Any plans for scratch mark removal? I might follow your steps here.
https://www.eevblog.com/forum/testgear/scored-this-keithley-191-multimeter-on-ebay/ (https://www.eevblog.com/forum/testgear/scored-this-keithley-191-multimeter-on-ebay/)
It's just that I have no idea how to do this sort of restoration, except for the electronics.
-
Any plans for scratch mark removal? I might follow your steps here.
https://www.eevblog.com/forum/testgear/scored-this-keithley-191-multimeter-on-ebay/ (https://www.eevblog.com/forum/testgear/scored-this-keithley-191-multimeter-on-ebay/)
It's just that I have no idea how to do this sort of restoration, except for the electronics.
Oh yea, gotta restore it. 8)
I'm trying to track down the display issue, hope to be back later today with some progress, gotta do some house chores though.
Oh, I just found while inspecting the board that the current protection fuse is blown. Every meter I get is like that LOL. :-//
-
Oh, I just found while inspecting the board that the current protection fuse is blown. Every meter I get is like that LOL. :-//
Every meter I use is like that at some point. :-BROKE
-
Oh, I just found while inspecting the board that the current protection fuse is blown. Every meter I get is like that LOL. :-//
Every meter I use is like that at some point. :-BROKE
Not my case. I'm proud I have only blown a single multimeter fuse in the last 3 years :-+
-
Another good oldie ! , I have a Keithley 177 re branded to a RACAL DANA 4003.
As Ivan noted check the transformer solder joints, not unusual to see dry joints on these older Keithley's !.
And I see you have those little spring loaded clamps too!. I have found many little jobs that require some holding pressure and these little things work like a champ, where the more traditional clamps just wont work.
-
Another good oldie ! , I have a Keithley 177 re branded to a RACAL DANA 4003.
As Ivan noted check the transformer solder joints, not unusual to see dry joints on these older Keithley's !.
And I see you have those little spring loaded clamps too!. I have found many little jobs that require some holding pressure and these little things work like a champ, where the more traditional clamps just wont work.
Yea I did check the transformer solder but it seems to be OK, but I'm beginning to think this guy has a few tricks up it's sleeve.
Back to the display issue, I measured about 4V on the 5V rail, but I also suspect it has fast fluctuations. When I inspected the 7805 regulator (VR104), it looked like Hell. It was really black and looked like it had overheated, so I pulled it. Since the 5V devices were then isolated from the transformer input, I hacked in an external 5V supply and connected it's ground it to the system ground, so it would act as a substitute 5V supply. When I did that, all the display problems went away and it looked beautiful. So I'm very pleased with that.
I then replaced the 7805 with a new one on hand ... but that did not fix the problem. :( Obviously, the issue is ahead of that component. It would seem the bridge is OK (supplying voltage) and I can't find anything wrong with it. So I'm still investigating what the cause is. Here is the schematic of the PS showing the +5V supply and +/- 15V supplies.
It's beer time now, so I'll listen to any suggestions anyone has and hit it again tomorrow. :)
(https://lh6.googleusercontent.com/-LYersSHWNBw/VPNGdq90AaI/AAAAAAAABuo/lrm0h0jW3Vs/w544-h556-no/PS_Notes.png)
-
Buzzing sound may indicate a short in the transformer perhaps!!. Although the +/- 15v were still coming from the transformer when you applied the external +5v ?.
There's not much to it though , transformer bridge electectro's and regulator.
Perhaps a bit of contact cleaner on the power and line selector switches to take care of any old age oxidation not causing intermittent contact.
-
Buzzing sound may indicate a short in the transformer perhaps!!. Although the +/- 15v were still coming from the transformer when you applied the external +5v ?.
Yep!
There's not much to it though , transformer bridge electectro's and regulator.
Perhaps a bit of contact cleaner on the power and line selector switches to take care of any old age oxidation not causing intermittent contact.
You're right - not much left. :-//
It's got to be a switch or cap or bad transformer. I should be able to isolate it tomorrow. Man, if it's just a simple thing this will be a steal. That's how you can score with these Ebay finds. People give up and just want to dump things for a song. I hope by posting these refurb threads it will give people some ideas and if they have the same instrument, some help with their own troubleshooting.
Also, it is dangerous poking around these things when they are connected to the mains - so if anyone out there is just getting into the hobby -be careful! :-/O
Anyway - we will see! 8)
-
The power supply section is pretty much identical to the Keithley 191. I too suspected a dried cap when I had a similar problem, but as I said, it turned out to be a cracked join. I don't know how you will be able to detect a short in the transformer, though. If the switch contacts aren't gold plated, my next bet is the switches.
-
Fixed!
I focused on C108 - 2200 uF cap. Thought it may have been bad so I connected another large cap in parallel with it, but that made no difference. Then, having noticed how bad some of the solder joints were here and there, I tried another test. I connected the positive lead of the cap I had placed in parallel to the far end of the trace it was supposed to be connected to, and the problem was fixed. Looking at the board with a magnifying glass, I saw that the trace was completely cracked right where the + end of the original cap was soldered. I then simply ran a new wire to the far end of the trace and the problem was fixed.
You can see pics of that below. You can also see pics of C108, and how they nicely soldered it "upside down" so you can't see the markings on it. Why do they do that?
Now I will inspect the board further and make sure there are no other obvious issues. Then I can check whether it really measures what it's supposed to, and the cal, and see exactly where I stand on this - whether or not this baby is going to be a useful DMM, but it's looking pretty promising now. I then will proceed to cosmetically clean it up and fix broken plastic - of which I just found another part about to break off yesterday. I will show that and what product I use to fix this kind of plastic.
(https://lh6.googleusercontent.com/-W7pMNZA1PR8/VPRqRgHmUNI/AAAAAAAABvo/cVGoDlyETeE/w565-h567-no/PS_fix.png)
(https://lh5.googleusercontent.com/-TSd7mC8haD4/VPJQD4N4X6I/AAAAAAAABtY/oFGarFFnIjs/w1024-h768-no/IMG_0656.png)
(https://lh3.googleusercontent.com/-NdLuRGIo1TE/VPNer6UnwxI/AAAAAAAABvQ/a9V5kwiCn5A/w1024-h768-no/IMG_0660.png)
(https://lh4.googleusercontent.com/-FmDqL-R6V_g/VPRqRwYF-6I/AAAAAAAABv0/FCB12zRQTx8/w1024-h768-no/IMG_0662.png)
-
Found this on the bottom. Looking at the pinouts of the switches, it connects pin 9 of the "20" switch with pin 7 of the "200" switch. On the schematic, it does show these pins connected with a hard connection. It just doesn't look like a factory installed wire though. I'd be interested if anyone else has a meter like this with this wire.
(https://lh6.googleusercontent.com/-f-G7phksdl4/VPR0YgYOP2I/AAAAAAAABwM/4gPbzNRWts0/w1024-h768-no/IMG_0663.png)
-
Wow, there are so many lifted pads in that last photo!! Have you checked every one of them for broken traces?
McBryce.
-
Wow, there are so many lifted pads in that last photo!! Have you checked every one of them for broken traces?
McBryce.
Yes I did McBryce. After what I found above, yes, I inspected
every
single
one.
With a magnifying glass. However, the proof is in the pudding, so to speak, so later today I'm going to compare this meter to my Rigol and see how it reads before I calibrate it. Then I'll find out if anything more is amiss. But as of right now, this basket case is starting to look like a real steal. But that's just the electronics, I have barely even begun to restore it, so keep looking here for a lot more pics of the restoration. :)
-
I will. The 179 is the device I used in University, so I've been toying with the idea of getting one to restore for myself. Just to bring back the memories.
McBryce.
-
What could have lifted so many pads? It seems to me the lifted pads are only there on larger, heavier components. Vibration?
-
What could have lifted so many pads? It seems to me the lifted pads are only there on larger, heavier components. Vibration?
I don't really know. If anyone else has one I'd like to know if the circuit board is in the same condition.
-
Dropped in a rack onto a concrete floor, so there is no case damage but the insides are heavily jarred. Or on a bench and had a few falls onto a carpeted floor.
-
Dropped in a rack onto a concrete floor, so there is no case damage but the insides are heavily jarred. Or on a bench and had a few falls onto a carpeted floor.
Yea could be, because it actually does have case damage and a cracked handle. Those are the next things I'm going to tackle (cosmetics) because it's looking like this meter is going to be a winner. I'll be showing the case damage and how I fix it in the coming days. :)
-
A quick check shows we got a winner! After all these years and abuse it's not bad! I'll go through the cal procedure later, but I'm very happy that it's going to live again! :clap:
(https://lh5.googleusercontent.com/-Geb7iXSPnfc/VPXRhAAq79I/AAAAAAAAByE/Kq8Q6jw4PAI/w654-h490-no/IMG_0673.png)
-
Hopefully you are going to adjust that...
-
Just in case you were wondering what that unused dip socket at the front RHS was for. It was the connection to the optional GPIB interface PCB which was used in a number of instruments ie 179 ser 24000 and up , 177 ser 16500 and up, 480 picoammeter. The model number for the option was 1793.
-
It would probably be a good idea to let a drop of superglue wick under each of those lifted pads to get them immobilized.
-
Congratulations on getting it running.
Aren't those lifted pads on the pins of the selection switches? They've probably just lifted due to years of being pressed.
McBryce.
-
Just in case you were wondering what that unused dip socket at the front RHS was for. It was the connection to the optional GPIB interface PCB which was used in a number of instruments ie 179 ser 24000 and up , 177 ser 16500 and up, 480 picoammeter. The model number for the option was 1793.
Interesting - Looking at the schematic and a quick flick through the 30535D(Model1793).pdf (http://www.keithley.com/support/data?asset=951) manual shows it would be very easy indeed to knock up an equivalent with a microcontroller. Ignore all the GPIB stuff like addressing and just implement the talk only mode at 2.5 readings/second. Use an 8 bit data bus to read in OVER, /STROBE, B1, B2, B4, B8, D5 and SIGN from J1008 dip connector and get the +5V power too. /STROBE is the latch. D5 indicates the first digit of five. B1-8 are BCD. Do some simple ASCII conversion to the same spec as detailed in 3.8 DATA FORMAT, and finally send it out a serial port to an opto-isolated RS232 interface much the same as all those cheap DMMs do.
Nice little project. :-+
-
Hopefully you are going to adjust that...
Well of course. Right before it's all ready to be put back together.
Just in case you were wondering what that unused dip socket at the front RHS was for. It was the connection to the optional GPIB interface PCB which was used in a number of instruments ie 179 ser 24000 and up , 177 ser 16500 and up, 480 picoammeter. The model number for the option was 1793.
Thanks.
It would probably be a good idea to let a drop of superglue wick under each of those lifted pads to get them immobilized.
I'll try that thanks.
Aren't those lifted pads on the pins of the selection switches? They've probably just lifted due to years of being pressed.
Maybe, those switches have a lot of pins, and the pins are pretty big wire. But anything's possible.
Interesting - Looking at the schematic and a quick flick through the 30535D(Model1793).pdf (http://www.keithley.com/support/data?asset=951) manual shows it would be very easy indeed to knock up an equivalent with a microcontroller. Ignore all the GPIB stuff like addressing and just implement the talk only mode at 2.5 readings/second. Use an 8 bit data bus to read in OVER, /STROBE, B1, B2, B4, B8, D5 and SIGN from J1008 dip connector and get the +5V power too. /STROBE is the latch. D5 indicates the first digit of five. B1-8 are BCD. Do some simple ASCII conversion to the same spec as detailed in 3.8 DATA FORMAT, and finally send it out a serial port to an opto-isolated RS232 interface much the same as all those cheap DMMs do.
Nice little project. :-+
Good info thanks. I'll post some pics later today because I'm starting to restore the case now. Hopefully it will be interesting to some people.
Well here's one. I got an ultrasonic cleaner from Harbor Freight a few years ago. It really cleans things well. I pulled off the button covers and threw them in it. I just put a few drops of dish soap in. It's amazing what dirt flies off when the cleaner is turned on. Highly recommended for cleaning all kinds of things. :-+
(https://lh5.googleusercontent.com/-5t7e4-3Dk00/VPNerE0XaHI/AAAAAAAABvE/aKUIC4LGMqw/w768-h576-no/IMG_0658.png)
-
Good info thanks. I'll post some pics later today because I'm starting to restore the case now. Hopefully it will be interesting to some people.
Well here's one. I got an ultrasonic cleaner from Harbor Freight a few years ago. It really cleans things well. I pulled off the button covers and threw them in it. I just put a few drops of dish soap in. It's amazing what dirt flies off when the cleaner is turned on. Highly recommended for cleaning all kinds of things. :-+
That looks very interesting indeed:
http://www.harborfreight.com/25-liter-ultrasonic-cleaner-95563.html (http://www.harborfreight.com/25-liter-ultrasonic-cleaner-95563.html)
But that sort of takes some space on the bench, doesn't it? Anyway, I'll be looking for the before/after comparison. And I guess I'll have to use a toothbrush and soap in my case.
-
Careful of the ultrasonic cleaner on some things. it can take paint off and destroy certain plastics.
-
And I guess I'll have to use a toothbrush and soap in my case.
Funny you should mention toothbrushes, I took some pics of what I do to some of my used toothbrushes. I like to bend the handles of some, because it makes them easier to use in certain circumstances. Just stick the brush part in a vise and grab a propane torch, and heat right behind the brush part and bend the handle up to whereever you like. The plastic is surprisingly tough, but it will bend.
Some of these bent brushes are really useful - plus, who doesn't like melting plastic with a torch? ;)
(https://lh3.googleusercontent.com/-Rdj00oXlseA/VPcttrNYxrI/AAAAAAAAB0A/J1NOn577HzY/w1024-h768-no/IMG_0675.png)
(https://lh6.googleusercontent.com/-jDUqXxS91LE/VPctuUUs4zI/AAAAAAAAB0E/v7jtgXuvcWc/w1024-h768-no/IMG_0676.png)
-
The third one looks like it would have been good for a few more weeks of dental care :D
McBryce.
-
I just use new tooth brushes. They are cheap enough, and you often find a sale where you get 5 in a pack for the price of 2, or I just order them wholesale. That way you do not get contaminants in the work you are cleaning.
-
I use used toothbrushes. It's more important that you have several of them, so that you don't use a toothbrush with etching fluid remnants to clean switch contacts etc. I doubt any "dental contamination" would effect the electronics.
McBryce.
-
I just use new tooth brushes. They are cheap enough, and you often find a sale where you get 5 in a pack for the price of 2, or I just order them wholesale. That way you do not get contaminants in the work you are cleaning.
Contaminated with what? My used toothbrushes are only "contaminated" with whatever was in my mouth, which I don't think is contaminated enough to have any effect whatsoever on what I'm using them to clean after I discard them. Even if there was some sort of residue, I can just throw it in my ultrasonic cleaner.
Besides, as soon as you start cleaning anything with a new toothbrush it's contaminated with the dirt you have just loosened. If you want to buy new toothbrushes go for it, but as far as my work goes, my used toothbrushes are just peachy keen. :-//
-
I really like the idea of bending the handles, will bend some.
-
I really like the idea of bending the handles, will bend some.
My dental hygienist just bends those same Oral B tooth brushes with her hands.. to reach where she needs to.. she showed me, she said they are designed to bend there. Maybe heating them up is not necessary? Now I just follow her, and bend them myself without heating.
-
Hot water works really well to soften plastic without burning. I recently used an old but 'clean' toothbrush but ended up getting small amounts of dried toothpaste on the board. So I have gone new/cheap route.
-
My dental hygienist just bends those same Oral B tooth brushes with her hands.. to reach where she needs to.. she showed me, she said they are designed to bend there. Maybe heating them up is not necessary? Now I just follow her, and bend them myself without heating.
Oh I can bend them, but they won't stay bent, at least not to the position I want. Hey do it however you want. :)
Anyway, moving on from toothbrushes, I'm proceeding to the restoration. I'm going to make it as original and clean as I can. Hence I am gluing back on the label that fell off the transformer. I'm polishing the red plastic window with some DVD disc polish I got from the now bankrupt Radio Shack (R.I.P.). It works really well and makes it like glass. Also, I'm removing all the old cal labels and any other gooy stuff with Goo Gone. Some of the dried label adhesive is very hard to get off, but if you let it set all day it will come off. Another thing you can do is put the Goo Gone on and then place a small piece of saran wrap on top of the Goo Gone so it won't evaporate and leave it all day. This is another use for a toothbrush because the plastic bristles will not scratch the plastic but will scrub well.
(https://lh3.googleusercontent.com/-HlXZzFUGiCM/VPNercFthdI/AAAAAAAABvM/GIf7rAyaS3U/w1024-h768-no/IMG_0659.png)
(https://lh4.googleusercontent.com/-PXd4pdRqRIc/VPXRhhZl7cI/AAAAAAAAByI/c0cp4g2RBOk/w1024-h768-no/IMG_0671.png)
(https://lh6.googleusercontent.com/-NW_-m_5rJXs/VPW4liADugI/AAAAAAAABxA/i0EtdIfDmyY/w1024-h768-no/IMG_0664.png)
-
How did you remove the scratch marks from the front panel overlay?
Are you gonna do anything to the 7 segment display? (is it faded?)
-
How did you remove the scratch marks from the front panel overlay?
I used as much polish as I dared to use on the overlay, I don't want to damage it. It's about as good as it can get at this point.
Are you gonna do anything to the 7 segment display? (is it faded?)
It works perfectly now that the 5V supply is fixed - good as new.
-
I don't think I can get a hold of that goo gone in the DR. I'll have to improvise.
Does anybody reckon this will work?
http://lifehacker.com/5931843/diy-goo-gone (http://lifehacker.com/5931843/diy-goo-gone)
-
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.
-
Yea I think it's based on citrus oils. I also saw some substitutes on the web made out of cooking oil or coconut oil, don't know if they would work as well. Just go buy some citrus degreaser and try it. :-//
-
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 (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'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 (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. :)
-
Input terminals cleaned up and re-installed.
Next on stage - MEK (methyl ethyl ketone) meets plastic. :box:
(https://lh3.googleusercontent.com/-qBbpjsIyoi8/VPhtMVvYbPI/AAAAAAAAB0w/eTTtuvbPXtw/w1024-h768-no/IMG_0677.png)
-
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. :clap:
(https://lh3.googleusercontent.com/-RRpM_oQ4JvU/VPRqSDMbTzI/AAAAAAAABv4/Qsc-rBcH6rs/w1024-h768-no/IMG_0661.png)
(https://lh5.googleusercontent.com/-VxmkNNbpWWw/VPW4n9LJZaI/AAAAAAAABxg/0-T-0OdApyc/w1024-h768-no/IMG_0669.png)
(https://lh3.googleusercontent.com/-QgPVZZaNqTo/VPW4oVJt5NI/AAAAAAAABxk/IcaXgYKEkXU/w1024-h768-no/IMG_0670.png)
(https://lh3.googleusercontent.com/-lWXu4SfeQWo/VPW4mukIhxI/AAAAAAAABxQ/X2e7kVx08Cs/w1024-h768-no/IMG_0667.png)
(https://lh4.googleusercontent.com/-efchx_tpX68/VPW4lVH2zgI/AAAAAAAABw8/GQ7LjqREcGo/w1024-h768-no/IMG_0666.png)
(https://lh6.googleusercontent.com/-u0mWGdKy9Pc/VPW4nGH5CbI/AAAAAAAABxY/Vek07_QYm-k/w1024-h768-no/IMG_0668.png)
-
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.
-
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.
-
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.
(https://lh5.googleusercontent.com/-Dbct4aK8ZJw/VPXRg57pcKI/AAAAAAAAByA/Kww5fes-Yis/w1024-h768-no/IMG_0672.png)
(https://lh6.googleusercontent.com/-Qd_pZ6fe8NY/VPW4mDOrGxI/AAAAAAAABxI/ZBWsTbSrTe0/w1024-h768-no/IMG_0665.png)
-
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 (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.
-
Did the bottom sticker remained intact even with the warm water and soap wash?
-
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! 8)
-
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.
(https://lh3.googleusercontent.com/-c4TuOZd2OAI/VPhtOWxDyxI/AAAAAAAAB1I/N56KZnmc3P0/w768-h576-no/IMG_0682.png)
(https://lh3.googleusercontent.com/-XCtk9KhrUAM/VPhtM1-l9jI/AAAAAAAAB00/B4lSNVGCCfc/w768-h576-no/IMG_0680.png)
-
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).
(http://i.ebayimg.com/00/s/OTYwWDEyODA=/z/7ewAAOSwEeFU-1XP/$_57.JPG)
(http://i.ebayimg.com/00/s/OTYwWDEyODA=/z/BroAAOSwBahU-1QN/$_57.JPG)
-
Good way to fill up emplty bench space, huh? O0
-
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. :clap:
-
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
-
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.
-
Calibration done -
(https://lh4.googleusercontent.com/-QTGfLxkhyBY/VPhtM435fII/AAAAAAAAB04/gMYiqE3tK2w/w1024-h768-no/IMG_0679.png)
-
Project done! Looks good and fully functional.
Going back - this is what I got in the mail - broken case parts and not working -
(https://lh5.googleusercontent.com/-CiICXMGDNqQ/VPIDtsNNj2I/AAAAAAAABsU/N-hgwvkzvOc/w1024-h768-no/IMG_0650.png)
(https://lh3.googleusercontent.com/-nco4qIqPxGI/VPhtN3HIFvI/AAAAAAAAB1E/Htt1_foEZX0/w1024-h768-no/IMG_0681.png)
(https://lh6.googleusercontent.com/-RAzMGWN_Dys/VPuBTD3DLVI/AAAAAAAAB20/VY5YbR9rKPs/w1024-h768-no/IMG_0688.png)
(https://lh4.googleusercontent.com/-GzSrxOYzR6M/VPuBS-rokSI/AAAAAAAAB24/VPuA-Edob4I/w1024-h768-no/IMG_0689.png)
(https://lh3.googleusercontent.com/-pBnmZ8aAH94/VPuBTRh3MFI/AAAAAAAAB28/KifcCyl2z7Q/w1024-h768-no/IMG_0690.png)
-
It even looks shiny! :clap:
-
Excellent work xrunner, that's one you can be proud of.
McBryce.
-
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. :-DMM Look for a new project w/pics tomorrow on this same board.
(http://www.srkresidency.com/images/coming-soon%20(1).jpg)
-
Good job
-
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%
-
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:
Looks like I need to take home some MEK.
-
Have you got a source for that info? While looking I found this:
http://www.plasticsintl.com/plastics_chemical_resistence_chart.html (http://www.plasticsintl.com/plastics_chemical_resistence_chart.html)
-
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.