On Tue, 08 Dec 2015 08:36:42 -0800, John Larkin <jjlarkin@highlandtechnology.com> wrote:>Might the weight of the needle affect the meter linearity?The counterbalance has to be adjusted or more than linearity will be affected: <http://www.herrong.com/KH200_COLOR.jpg> The counterbalance is the orange blob opposite the needle. Others are made from a piece of solid wire. Some are adjustable, but most are just preset. It's difficult to get this right because the springs affect the adjustment. The replacement needle will probably be heavier than the original. So, some mass needs to be added to the counterbalance. The easiest way is apply tiny blobs of viscous epoxy to the counterbalance while rotating the meter to different positions. If it's off balance, the needle will move when the meter is rotated 90 degrees vertically. If it's properly balanced, the reading will not change. See section on meter balancing in: Rejuvenating Old Meters February 1943 QST Article <http://www.rfcafe.com/references/qst/rejuvenating-old-meters-feb-1943-qst.htm> Finding a suitable replacement needle is a problem. If I don't care about accuracy or looks, I just use a piece of stiff stainless wire. If I want perfection, I cannibalize another similar meter. Another major problem is finding a clean work area. The meter magnet really attracts difficult to remove junk. I usually don't need to replace the needle. It's made from brass and will bend back into shape as long as it's not excessively mangled. Flat duck-bill tweezers seem to work well for needle straightening. In the distant past, I used to do this type of precision work without much difficulty. Today, my eyesight and steady hand have deteriorated to the point where I'm not sure I still can do it. It's been many years since I've replaced a meter needle. I couldn't find any YouTube videos on the process, which suggests that nobody is doing this level of repair. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Keithley 610C repair
Started by ●December 1, 2015
Reply by ●December 8, 20152015-12-08
Reply by ●December 8, 20152015-12-08
On Tue, 08 Dec 2015 09:42:10 -0800, Jeff Liebermann <jeffl@cruzio.com> wrote:>On Tue, 08 Dec 2015 08:36:42 -0800, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >>Might the weight of the needle affect the meter linearity? > >The counterbalance has to be adjusted or more than linearity will be >affected: ><http://www.herrong.com/KH200_COLOR.jpg> >The counterbalance is the orange blob opposite the needle. Others are >made from a piece of solid wire. Some are adjustable, but most are >just preset. It's difficult to get this right because the springs >affect the adjustment. The replacement needle will probably be >heavier than the original. So, some mass needs to be added to the >counterbalance. The easiest way is apply tiny blobs of viscous epoxy >to the counterbalance while rotating the meter to different positions. >If it's off balance, the needle will move when the meter is rotated 90 >degrees vertically. If it's properly balanced, the reading will not >change. See section on meter balancing in: >Rejuvenating Old Meters February 1943 QST Article ><http://www.rfcafe.com/references/qst/rejuvenating-old-meters-feb-1943-qst.htm> > >Finding a suitable replacement needle is a problem. If I don't care >about accuracy or looks, I just use a piece of stiff stainless wire. >If I want perfection, I cannibalize another similar meter. Another >major problem is finding a clean work area. The meter magnet really >attracts difficult to remove junk. > >I usually don't need to replace the needle. It's made from brass and >will bend back into shape as long as it's not excessively mangled. >Flat duck-bill tweezers seem to work well for needle straightening. > >In the distant past, I used to do this type of precision work without >much difficulty. Today, my eyesight and steady hand have deteriorated >to the point where I'm not sure I still can do it. It's been many >years since I've replaced a meter needle. I couldn't find any YouTube >videos on the process, which suggests that nobody is doing this level >of repair.Seems like buying a junker 610 would be easier. Buy two and you could probably make one good one, if you have time to play with it. Get a Mantis; it's fabulous for close work.I couldn't solder insane things like US8 packages without mine. https://dl.dropboxusercontent.com/u/53724080/Mantis/Bench_Mantis.jpg https://dl.dropboxusercontent.com/u/53724080/Mantis/Mantis2.JPG https://dl.dropboxusercontent.com/u/53724080/Mantis/MVC-277X.JPG https://dl.dropboxusercontent.com/u/53724080/Mantis/4xLens.JPG
Reply by ●December 8, 20152015-12-08
On Tue, 8 Dec 2015 12:22:08 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 12/08/2015 04:56 AM, RBlack wrote: >> On Tue, 01 Dec 2015 10:07:53 -0800, Jeff Liebermann (jeffl@cruzio.com) >> said: >>> On Tue, 1 Dec 2015 10:22:23 -0000, RBlack <news@rblack01.plus.com> >>> wrote: >>> >>>> Any advice? For $100 I'm tempted to take a gamble and have it delivered >>>> to our US office, one of our guys can bring it over next time he visits. >>>> OTOH if the parts are unobtainium I'll wait for a working one to appear. >>> >>> At $100, there's almost certainly something wrong with it. Still, >>> methinks it's worth trying to fix it. 610c manual at: >>> <http://122.physics.ucdavis.edu/course/cosmology/sites/default/files/files/Ferro%20Electricity/Keithley610manual.pdf> >>> The schematic is dated 1968 so I would suspect that the big >>> electrolytics in the power supply have dried out. If that doesn't do >>> the trick and it looks like the two input FETs are fried, carefully >>> remove them (using static protection) and replace them with whatever >>> you can find that's close, just to see if it works. If it works, but >>> leaks badly on the higher sensitivity scales, try to find suitable >>> substitute FETs. The manual does not list a replacement part number >>> for the input FETs, which are designated as part of the input PCB, >>> Keithley 23733A. However, the photo looks like they're easily >>> replaced: >>> <http://holzleitner.com/el/keithley-610c-electrometer/keithley-610c-input-section.jpg> >>> Note the black Fairchild xsistors above the FETs. They're epoxy >>> filled and might be IR light sensitive. >>> >>> Internal detail and photos: >>> <http://holzleitner.com/el/keithley-610c-electrometer/index-en.html> >>> >>> Calibration costs about $250 to $300 which might make it more >>> attractive to buy something that works and is calibrated. >>> >>> Interesting readings and photos: >>> <http://www.eevblog.com/forum/projects/electrometer-input-stage/> >>> >> >> I had a closer look on eBay's US site and as John L pointed out, there >> is more than one available - unfortunately all non-working. One has the >> meter glass missing, I don't think the movement would survive the >> shipping. The one I was originally looking at has the protective cap >> for the input connector missing, I'm assuming this is important for >> protection from contamination and ESD? >> >> Looking at the completed listings, 610Cs in complete working order don't >> sell for much more than the $100 being asked for the broken ones, so >> I'll wait for one of them to turn up. >> >> >> >They come along periodically. Inspired by this thread, I bought one >with a 30-day DOA warranty for a $125 (best offer) a week or so ago. >Should be here Thursday. > >Cheers > >Phil HobbsThat's amazing. Realistically, that instrument is worth kilobucks. Maybe I should get a spare before word gets out. The "fast" mode (TIA sort of feedback) has never worked on mine. Does it on yours? It's no big deal, just a longer settling time on the lower ranges.
Reply by ●December 8, 20152015-12-08
On 12/08/2015 12:52 PM, John Larkin wrote:> On Tue, 8 Dec 2015 12:22:08 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 12/08/2015 04:56 AM, RBlack wrote: >>> On Tue, 01 Dec 2015 10:07:53 -0800, Jeff Liebermann (jeffl@cruzio.com) >>> said: >>>> On Tue, 1 Dec 2015 10:22:23 -0000, RBlack <news@rblack01.plus.com> >>>> wrote: >>>> >>>>> Any advice? For $100 I'm tempted to take a gamble and have it delivered >>>>> to our US office, one of our guys can bring it over next time he visits. >>>>> OTOH if the parts are unobtainium I'll wait for a working one to appear. >>>> >>>> At $100, there's almost certainly something wrong with it. Still, >>>> methinks it's worth trying to fix it. 610c manual at: >>>> <http://122.physics.ucdavis.edu/course/cosmology/sites/default/files/files/Ferro%20Electricity/Keithley610manual.pdf> >>>> The schematic is dated 1968 so I would suspect that the big >>>> electrolytics in the power supply have dried out. If that doesn't do >>>> the trick and it looks like the two input FETs are fried, carefully >>>> remove them (using static protection) and replace them with whatever >>>> you can find that's close, just to see if it works. If it works, but >>>> leaks badly on the higher sensitivity scales, try to find suitable >>>> substitute FETs. The manual does not list a replacement part number >>>> for the input FETs, which are designated as part of the input PCB, >>>> Keithley 23733A. However, the photo looks like they're easily >>>> replaced: >>>> <http://holzleitner.com/el/keithley-610c-electrometer/keithley-610c-input-section.jpg> >>>> Note the black Fairchild xsistors above the FETs. They're epoxy >>>> filled and might be IR light sensitive. >>>> >>>> Internal detail and photos: >>>> <http://holzleitner.com/el/keithley-610c-electrometer/index-en.html> >>>> >>>> Calibration costs about $250 to $300 which might make it more >>>> attractive to buy something that works and is calibrated. >>>> >>>> Interesting readings and photos: >>>> <http://www.eevblog.com/forum/projects/electrometer-input-stage/> >>>> >>> >>> I had a closer look on eBay's US site and as John L pointed out, there >>> is more than one available - unfortunately all non-working. One has the >>> meter glass missing, I don't think the movement would survive the >>> shipping. The one I was originally looking at has the protective cap >>> for the input connector missing, I'm assuming this is important for >>> protection from contamination and ESD? >>> >>> Looking at the completed listings, 610Cs in complete working order don't >>> sell for much more than the $100 being asked for the broken ones, so >>> I'll wait for one of them to turn up. >>> >>> >>> >> They come along periodically. Inspired by this thread, I bought one >> with a 30-day DOA warranty for a $125 (best offer) a week or so ago. >> Should be here Thursday. >>> That's amazing. Realistically, that instrument is worth kilobucks. > Maybe I should get a spare before word gets out.<http://www.ebay.com/itm/151898747692> Boat anchors rock, like I done said. ;) It still isn't as cool as my 410, but it has a much better meter, and is way more practical generally.> > The "fast" mode (TIA sort of feedback) has never worked on mine. Does > it on yours?Dunno yet. I'll see. Usually there's enough capacitance around that it takes awhile to settle anyway. It's no big deal, just a longer settling time on the> lower ranges.Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●December 8, 20152015-12-08
On Tuesday, December 8, 2015 at 12:52:21 PM UTC-5, John Larkin wrote:> On Tue, 8 Dec 2015 12:22:08 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > >On 12/08/2015 04:56 AM, RBlack wrote: > >> On Tue, 01 Dec 2015 10:07:53 -0800, Jeff Liebermann (jeffl@cruzio.com) > >> said: > >>> On Tue, 1 Dec 2015 10:22:23 -0000, RBlack <news@rblack01.plus.com> > >>> wrote: > >>> > >>>> Any advice? For $100 I'm tempted to take a gamble and have it delivered > >>>> to our US office, one of our guys can bring it over next time he visits. > >>>> OTOH if the parts are unobtainium I'll wait for a working one to appear. > >>> > >>> At $100, there's almost certainly something wrong with it. Still, > >>> methinks it's worth trying to fix it. 610c manual at: > >>> <http://122.physics.ucdavis.edu/course/cosmology/sites/default/files/files/Ferro%20Electricity/Keithley610manual.pdf> > >>> The schematic is dated 1968 so I would suspect that the big > >>> electrolytics in the power supply have dried out. If that doesn't do > >>> the trick and it looks like the two input FETs are fried, carefully > >>> remove them (using static protection) and replace them with whatever > >>> you can find that's close, just to see if it works. If it works, but > >>> leaks badly on the higher sensitivity scales, try to find suitable > >>> substitute FETs. The manual does not list a replacement part number > >>> for the input FETs, which are designated as part of the input PCB, > >>> Keithley 23733A. However, the photo looks like they're easily > >>> replaced: > >>> <http://holzleitner.com/el/keithley-610c-electrometer/keithley-610c-input-section.jpg> > >>> Note the black Fairchild xsistors above the FETs. They're epoxy > >>> filled and might be IR light sensitive. > >>> > >>> Internal detail and photos: > >>> <http://holzleitner.com/el/keithley-610c-electrometer/index-en.html> > >>> > >>> Calibration costs about $250 to $300 which might make it more > >>> attractive to buy something that works and is calibrated. > >>> > >>> Interesting readings and photos: > >>> <http://www.eevblog.com/forum/projects/electrometer-input-stage/> > >>> > >> > >> I had a closer look on eBay's US site and as John L pointed out, there > >> is more than one available - unfortunately all non-working. One has the > >> meter glass missing, I don't think the movement would survive the > >> shipping. The one I was originally looking at has the protective cap > >> for the input connector missing, I'm assuming this is important for > >> protection from contamination and ESD? > >> > >> Looking at the completed listings, 610Cs in complete working order don't > >> sell for much more than the $100 being asked for the broken ones, so > >> I'll wait for one of them to turn up. > >> > >> > >> > >They come along periodically. Inspired by this thread, I bought one > >with a 30-day DOA warranty for a $125 (best offer) a week or so ago. > >Should be here Thursday. > > > >Cheers > > > >Phil Hobbs > > That's amazing. Realistically, that instrument is worth kilobucks. > Maybe I should get a spare before word gets out. > > The "fast" mode (TIA sort of feedback) has never worked on mine. Does > it on yours? It's no big deal, just a longer settling time on the > lower ranges.I've never had the fast feedback work on mine. It either pegs the needle, or causes it to vibrate rapidly. George H.
Reply by ●December 9, 20152015-12-09
On Tue, 08 Dec 2015 08:22:21 -0800, Jeff Liebermann (jeffl@cruzio.com) said:> On Tue, 8 Dec 2015 09:56:35 -0000, RBlack <news@rblack01.plus.com> > wrote: > > >I had a closer look on eBay's US site and as John L pointed out, > >there is more than one available - unfortunately all non-working. > >One has the meter glass missing, I don't think the movement would > >survive the shipping. The one I was originally looking at has > >the protective cap for the input connector missing, I'm assuming > >this is important for protection from contamination and ESD? > > It appears that you do not want to do much in the way of repair work.Guilty as charged. I actually enjoy repairing stuff as a break from design work, but my boss doesn't see it that way. If there were a bigger difference in price between the working and broken instruments, I might give it a try.> Replacing a BNC cover, meter glass, or even input FET's are not major > repairs.Sure, but without access to another instrument at least as capable as the 610C I would have no confidence I hadn't screwed up the repair. The next-best meter I have is a 34410A which (IIRC) can resolve hundreds of nanoamps and up to 10 megohms. I will go and buy some of the gigaohm and teraohm resistors which were mentioned a while back in any case, to sanity-check the instrument before I use it for Real Work. What type is the input connector BTW? It doesn't appear to be a BNC from the photos, it's threaded, similar to a N type but smaller and with serrations on the mating face. The manual just describes it as a co-ax connector.> Broken glass on meters will not destroy the meter movement, but might > destroy the needle. Attaching a new needle to the meter movement is > tricky, but not impossible. I've done it a few times. The real > danger is having scrap metal and dirt enter the meter movement causing > erratic operation. Fishing out the scrap metal requires a steady > hand, needle point tweezers, and a binocular microscope. I've done it > a few times. I've also replaced an analog meter with a digital panel > meter. > > >Looking at the completed listings, 610Cs in complete working order don't > >sell for much more than the $100 being asked for the broken ones, so > >I'll wait for one of them to turn up. > > Don't use eBay "Completed" listings. Use "Sold Listings". Completed > listings include those items that did not sell in the last 30 days > while sold listings go back 90 days. > <http://pages.ebay.com/help/search/questions/search-completed-listings.html> > <http://www.ebay.com/sch/i.html?_nkw=keithley%20610c&LH_Complete=1&LH_Sold=1> > Looks like $140 to $180 were the selling prices with 0 sold in Sept, 3 > sold in Nov, and 1 in Dec. You shouldn't have long to wait. > >
Reply by ●December 9, 20152015-12-09
>> Replacing a BNC cover, meter glass, or even input FET's are not major >> repairs. ��>Sure, but without access to another instrument at least as capable as >the 610C I would have no confidence I hadn't screwed up the repair.On a normal 4-3/4 digit, 10M DVM, the 400 mV range is also a 0-40 nA range with 1 pA resolution. Cheers Phil Hobbs
Reply by ●December 9, 20152015-12-09
On Wednesday, December 9, 2015 at 8:14:39 AM UTC-5, Phil Hobbs wrote:> >> Replacing a BNC cover, meter glass, or even input FET's are not major > >> repairs. � > � > >Sure, but without access to another instrument at least as capable as > >the 610C I would have no confidence I hadn't screwed up the repair. > > On a normal 4-3/4 digit, 10M DVM, the 400 mV range is also a 0-40 nA range with 1 pA resolution. > > Cheers > > Phil HobbsYup, and with a giga ohm resistor and a fet opamp you can measure pA, (as long as you don't mind subtracting an offset.) digikey has 1G's for a few bucks. The cheapest 1T I found was at mouser. ~$10. www.mouser.com/ProductDetail/Ohmite/MOX112523100AK/?qs=sGAEpiMZZMtlubZbdhIBIA3afoNhrXdmSEazpH%252bOWJQ%3d George H.
Reply by ●December 9, 20152015-12-09
On Wed, 9 Dec 2015 05:14:29 -0800 (PST), Phil Hobbs (pcdhobbs@gmail.com) said:> >> Replacing a BNC cover, meter glass, or even input FET's are not major > >> repairs. � > � > >Sure, but without access to another instrument at least as capable as > >the 610C I would have no confidence I hadn't screwed up the repair. > > On a normal 4-3/4 digit, 10M DVM, the 400 mV range is also a 0-40 nA range with 1 pA resolution. > > Cheers > > Phil Hobbs >Doh! Of course. Good tip, thanks.
Reply by ●December 9, 20152015-12-09
On Wed, 9 Dec 2015 10:32:46 -0000, RBlack <news@rblack01.plus.com> wrote:>Sure, but without access to another instrument at least as capable as >the 610C I would have no confidence I hadn't screwed up the repair.I believe the manual has a calibration procedure. I'm too lazy|busy to check right now.>What type is the input connector BTW? It doesn't appear to be a BNC >from the photos, it's threaded, similar to a N type but smaller and with >serrations on the mating face. The manual just describes it as a co-ax >connector.I screwed up. I don't currently own a 610C, although I've used one in the past. I thought it used a BNC connector, but upon closer inspection of some online photos, it appears to be a common SO-239. Sorry about the muddle: <http://www.recycledgoods.com/keithley-instruments-610c-solid-state-electrometer.html> -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
