EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: Zucca on February 22, 2014, 10:07:56 pm
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Hi EE dragons,
yes, I got a Keithley 220 from Ebay. It is not properly calibrated but it works! No repair needed, cool!
The manual is ... well what I can say? Now I strongly believe all the EE devices in paradise will have manuals like this ("Open Hardware" devices in the mid-80's!).
I'm so happy.
Now as always on used ebay gear I would like to clean out the dust and do a little of general service on the unit (check for not good looking elco caps etc.).
Since it my first freaking precision unit in my bench (the Agilent 34461A is in the pipe line as soon I get the money from selling my Suzuky) I post here something before damaging the unit in some inappropriate actions.
Here my cleaning process proposal:
1) Dust: I want first vacuum very gently the unit and the I plant to do a final touch with air compressed.
With fast moving air I will hold (or disconnect?) the fan to avoid induced voltage into the board.
2) Does it make sense to do a full IPA bath at home of the precision resistors board?? Yes I plan to rinse everything with virgin IPA at the end (I will use gloves and try to not contaminate with my salivation). I also got the idea to use an ultrasonic toothbrush, bah...
Should I save me time and stress and buy a used ultrasonic bath device? (you know an EE lab always needs a new devices and toys).
(PS: I searched for DIY IPA bath in google but I got just beer related results back)
What other steps I am missing? Any suggestions? How do you normally clean old stuff?
I searched for cleaning procedure on the blog but I found only isolated discussions and I am missing the full picture.
Here some pictures, yes it is in good shape:
(http://s30.postimg.org/tsi5jdl0h/IMG_0973.jpg)
(http://s15.postimg.org/nn5cakeyj/IMG_0968.jpg)
(http://s22.postimg.org/51goma3yp/IMG_0970.jpg)
@Admin: I just realized this discussion fits better in "general discussion". Sorry for that.
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Nice purchase!
You may want to review:
http://thesignalpath.com/blogs/2012/11/26/teardown-repair-and-calibration-of-a-keithley-220-programmable-current-source/ (http://thesignalpath.com/blogs/2012/11/26/teardown-repair-and-calibration-of-a-keithley-220-programmable-current-source/)
I think Shahriar raises some concerns about getting contamination on critical parts that may impact the terra-ohm impedance of the unit.
From the pictures it looks like a really nice unit - enjoy.
Rastro
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Thanks Rastro, I love that review. I also read this post:
https://www.eevblog.com/forum/testgear/video-teardown-repair-and-cal-of-a-keithley-220-programmable-current-source/msg166849/#msg166849 (https://www.eevblog.com/forum/testgear/video-teardown-repair-and-cal-of-a-keithley-220-programmable-current-source/msg166849/#msg166849)
Shahriar reveals he used an ultrasonic bath to clean up the unit. But I have no ultrasonic bath in my lab...
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If it's clean and working well leave it as it is. This is an extremely high impedance device. Greater than 1014 ohm! I think an IPA rinse will degrade it's performance. The solved dirt in the IPA will contaminate the high impedance circuit. Even on a bench multimeter (1010 - 1012 ohm) an IPA rinse can make things worse.
Generally avoid any contamination. Don't touch the high impedance circuit, Don't breath on it, etc.
btw: manual describes the cleaning procedure:
5.8.1 Servicing High Impedance Circuitry
High impedance circuitry is extremely sensitive and must be
kept clean of oil, dirt, dust and contaminants. Replacing a
component or components within a high impedance circuit
requires special cleaning and handling to maintain the high
impedance level of the circuit. After replacing any compo-
nent in the high impedance circuitry, or if the high impe-
dance circuitry (InA-1rA range resistors) are contaminated,
use the following procedure to clean the circuit:
1. Clean the entire high impedance circuit with methanol
and a clean cotton swab.
2. Blow dry the circuit with dry nitrogen gas.
3. Inspect the circuit for any residue (contamination) and
repeat steps 1 and 2 if any residue is found.
4. Reassemble taking care not to touch the clean com-
ponets
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What is this IPA?
For me so far, IPA is an fairly hoppy and strong beer :)
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What is this IPA?
For me so far, IPA is an fairly hoppy and strong beer :)
isopropyl alcohol
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ah!
Ok, here in Norway, it's not easy to get that for private use, I have small amounts of it that I use with an brush.
Since you say bath, does it mean that you have access to abundant volumes of this fairly cheaply to bath pcb's in it?
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Right now I´m in USA. Here if have money there is pretty much only the law limit.
Yes I could have lot of IPA 99% but I don´t know if I will soak that insane precision PCB in it.
I will probably end up with compressed air, since there is a fan in the unit I will surely not damage anything.
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You can substitute methylated spirits for IPA if need be, not as good but does the job. Cheap as well. Just do not drink it.
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What is this IPA?
For me so far, IPA is an fairly hoppy and strong beer :)
India Pale Ale :)
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ah!
Ok, here in Norway, it's not easy to get that for private use, I have small amounts of it that I use with an brush.
Since you say bath, does it mean that you have access to abundant volumes of this fairly cheaply to bath pcb's in it?
I'd sort of assume that any chemical supply store or decently large electronics supply to have large quantities at low prices, though I've yet to find one cheaper than Costco (packages of 4*500mL) in my city.
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Is it really a problem for you Skandinavians to access alcohol based cleaners? Here in Germany and probably the rest of the old world too you can easily order IPA via ebay or several shops. It is a very common medium for any kind of use, from cleaning to desinfection to thinning paints that have to dry up very fast. I ordered 5 liters for about 15€ from ebay the last time. This was not even the cheapest one but a shop I knew. As a tip: It is used often in the process of making french nails. The cheapest stuff you can get (about 95% typically) is for that use. Huge market on ebay.
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You can substitute methylated spirits for IPA if need be, not as good but does the job. Cheap as well. Just do not drink it.
Meths will tend to leave residues.
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True, but good for dirty cleaning and then you can use the IPA for a final wash.
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Is it really a problem for you Skandinavians to access alcohol based cleaners? Here in Germany and probably the rest of the old world too you can easily order IPA via ebay or several shops. It is a very common medium for any kind of use, from cleaning to desinfection to thinning paints that have to dry up very fast. I ordered 5 liters for about 15€ from ebay the last time. This was not even the cheapest one but a shop I knew. As a tip: It is used often in the process of making french nails. The cheapest stuff you can get (about 95% typically) is for that use. Huge market on ebay.
Earlier you needed some sort of license to buy it, maybe it's changed.
So far I have bought pads that i use, but they leave lint often, but what ebay seller did you order from?
I did a search now, nothing close to that price came up, but I thought shipping would be an issue, say, it's getting more and more dificult to ship batteries, what would 5 liters of alcohol do?
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Is it really a problem for you Skandinavians to access alcohol based cleaners? Here in Germany and probably the rest of the old world too you can easily order IPA via ebay or several shops. It is a very common medium for any kind of use, from cleaning to desinfection to thinning paints that have to dry up very fast. I ordered 5 liters for about 15€ from ebay the last time. This was not even the cheapest one but a shop I knew. As a tip: It is used often in the process of making french nails. The cheapest stuff you can get (about 95% typically) is for that use. Huge market on ebay.
Pure IPA (99.5%) and denatured ethanol is no problem in sweden, norway might be different...
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As an aside, where does one get the air filters for these units? I have a 230 with no filter on it.
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Rødsprit is what they call denatured ethanol, but that has additives, or is that ok for cleaning maybe?
I have only used isopropyl alcholol (isopronalol) so far, but what I have I got from someone who "stole" it from their work.
But I found one supplier, they only sells to companies, but they have it for $34 / €25 pr liter, before shipping and such.
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As an aside, where does one get the air filters for these units? I have a 230 with no filter on it.
wouldn't something like this do? http://www.ebay.com/itm/390722403763 (http://www.ebay.com/itm/390722403763)
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Rødsprit is what they call denatured ethanol, but that has additives, or is that ok for cleaning maybe?
Ethanol is the alcohol which people drink. It is "denatured" usually by adding small amounts of other solvents, often just IPA. This is to make it undrinkable and thereby avoid it from being taxed as liquor. Check the MSDS, but it should still work fine for cleaning.
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Denatured ethanol (Rødsprit ) contains: etanol: 60 - 100 %, butanon: 5 - 7 %, Aceton: 2 - 3 %
And another version for fireplaces contains: etanol: 60 - 100 %, 4-metyl-2-pentanon: 1 - 5 %, 2-propanol: 1 - 5 %, etylacetat: 1 - 5 %
60-100%.. hm
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If it's clean and working well leave it as it is. This is an extremely high impedance device. Greater than 1014 ohm! I think an IPA rinse will degrade it's performance. The solved dirt in the IPA will contaminate the high impedance circuit. Even on a bench multimeter (1010 - 1012 ohm) an IPA rinse can make things worse.
You should listen to this. Save the alcohol baths for extreme cases.
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I start with household soap for cleaning the casing etc. In my experience ethanol is much stronger than IPA. Ethanol works great for really greasy substances but may damage plastics. I usually blow the dust from PCBs with compressed air. Cleaning is prone to causing damage due to ESD and brittle solder joints.
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As an aside, where does one get the air filters for these units? I have a 230 with no filter on it.
wouldn't something like this do? http://www.ebay.com/itm/390722403763 (http://www.ebay.com/itm/390722403763)
hmmm.. might do but it looks too thick at 10mm.
Keithley recommendations for high impedance components are cleaning with Methanol using cotton swap and then blow drying with nitrogen gas. Persoanlly, I would just blow with compressed air and leave well enough alone.
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Persoanlly, I would just blow with compressed air and leave well enough alone.
Yeah, I like it. As I said the fan is blowing air in the unit. I can not go wrong.
Here my filter (cleaned, there were so many dead zombies in it...)
(http://s9.postimg.org/vpps43cyn/IMG_1010.jpg)
it's about 5.5mm thick.
To me it looks too light, maybe 80's technology? I am tempted to do an upgrade with a more fine one...
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There is a reason they say use dry nitrogen. The air from your compressor will contain moisture and oil vapor (unless it is a diaphragm version) that is not the same as ambient air that the fan draws in.
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What about a hair dryer ??? ? :-DD Thanks robrenz for your patience and support, I´m learning a lot from you!
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ah!
Ok, here in Norway, it's not easy to get that for private use, I have small amounts of it that I use with an brush.
Since you say bath, does it mean that you have access to abundant volumes of this fairly cheaply to bath pcb's in it?
For some years now, teknisk sprit, etanol, has been free to sell and buy from paintstores. Has to be orderd to the most of them since they not Stock it. Before you had to have a permit and order it tru a monol, but not anymore. Its regulated tru EU, the comon marked regulations. I order it and pay around 50kr pr litre.
Wow, cool!, Then I can go to my paintshop, Flugger and ask, I got some way back, and was told then that people using it had to have an license from the police to buy it, so I newer checked again.
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Yeah, that's Norway alright :)
Way easier to get moonshine (atleat before) than do it the legal way.
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...Depressing picture of Insanity...
Damn, I always had the impression Norway would be pretty cool and free about stuff. It looks worse than the Cold War USSR from this!. No wonder your cost of living and taxes are so insane. Just what purpose do these interfering bureaucrats serve for society? You should resurrect the viking spirit and get rid of these controlling politicos by the sword, by Odin! Summon Thor to zap them all with lightning!
Why, a Norseman should be able to drink pure IPA for breakfast - right from the skull cup of one of his vanquished enemies! ;D Worship Odin and drink any form of alcohol from skulls. It's all part of the EU human rights act I am sure.
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I think this air compressor setup described by Aurora for cleaning lenses will do the job:
https://www.eevblog.com/forum/reviews/flir-e4-the-useful-information-thread/msg337307/#msg337307 (https://www.eevblog.com/forum/reviews/flir-e4-the-useful-information-thread/msg337307/#msg337307)
- Oil less
- water vapour separator
- more
and it is not so expensive... I like it!
Now it´s time for some IPA drink again...
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Is it really a problem for you Skandinavians to access alcohol based cleaners? Here in Germany and probably the rest of the old world too you can easily order IPA via ebay or several shops. It is a very common medium for any kind of use, from cleaning to desinfection to thinning paints that have to dry up very fast. I ordered 5 liters for about 15€ from ebay the last time. This was not even the cheapest one but a shop I knew. As a tip: It is used often in the process of making french nails. The cheapest stuff you can get (about 95% typically) is for that use. Huge market on ebay.
I Scored!, I found an german seller on ebay that sold med 5 litres of 99% ipa, got it today, second shipment, the first got lost somehow.
€12.49 + €15 in shipping, very cheap and easy, I was afraid of an big customs bill, but seems like I got away with it.
Now to find ways to dispense this, 5 liters is kinda big jug.. :)
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The first shipment that got lost will be easy to find, just look for the blind postman.