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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Anyone know how these old singer foot pedals work? There's not much
to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete |
#3
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wrote:
Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. The contact resistance between the carbon discs is varied by the pressure on the stack (in a similar way to the action of a carbon microphone). There will be some sort of compression spring between the operating lever and the top of the stack (it might be a leaf spring). When the spring is almost fully compressed, a contact by-passes the resistance stack and gives full power. It sounds as though the compression system isn't functioning or the by-pass contacts are closing too quickly. You need to identify an adjustment screw somewhere in the linkage to the compression spring and set up the pressure on the stack so that the compression is minimal when contact is first made with the stack and increases until the motor is nearly at full power before the by-pass contacts close. I can supply a photograph of the inside of the controller for a 1950s Model 201K (for 150 to 250 volt operation) if that would help you. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#4
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lid (Adrian Tuddenham) writes:
wrote: Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. The contact resistance between the carbon discs is varied by the pressure on the stack (in a similar way to the action of a carbon microphone). There will be some sort of compression spring between the operating lever and the top of the stack (it might be a leaf spring). When the spring is almost fully compressed, a contact by-passes the resistance stack and gives full power. It sounds as though the compression system isn't functioning or the by-pass contacts are closing too quickly. You need to identify an adjustment screw somewhere in the linkage to the compression spring and set up the pressure on the stack so that the compression is minimal when contact is first made with the stack and increases until the motor is nearly at full power before the by-pass contacts close. I can supply a photograph of the inside of the controller for a 1950s Model 201K (for 150 to 250 volt operation) if that would help you. It may also be possible to simply buy a replacement foot-pedal rheostat but it would have to be matched up in terms of resistance range. Of course, if you want authenticity, you'll have to repair it! -- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#5
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No one has said anything about replacing the pot with an SCR or triac
controller. |
#6
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On Thu, 23 Apr 2009 04:20:31 -0700, "William Sommerwerck"
wrote: No one has said anything about replacing the pot with an SCR or triac controller. Sacrilege! It's probably an antique Singer sewing machine. Trends towards modernization of antiques are highly discouraged by convention among collectors. The desecrations of cherished antiques never seems to end. The slippery slope of modernization and evil upgrading will soon lead to the total replacement of the entire sewing machine. Such things cannot be tolerated. Maintaining an old machine is an art. Doing the same to a modern plastic equivalent is often a waste of time. Best to restore the old Singer to its original condition than to butcher it into some manner of hybrid contrivance. It's a marginal idea anyway. Small sewing machine motors use solid carbon brushes. That's fine for low duty cycle, variable speed, and minimal load motors. Add an electronic speed control and the brushes now see a higher frequency component in the wave form. The result is a slight increase in arcing of the brushes, which causes increased wear of the copper commutator sections. Modern brushes are a sandwich of graphite (for lubrication) and carbon (for conductivity) to prevent this type of wear. My guess(tm) is that an electronic speed control will take about 25% off the life of the motor. Some instructions and clues on rebuilding sewing machine motors: http://reviews.ebay.com/HOW-TO-OVERHAUL-YOUR-SEWING-MACHINE-MOTOR-IN-30-MINUTES_W0QQugidZ10000000004665359 "The next step is to clean the armature commutator. This is where the carbon brushes make contact. 90% of motor's troubles comes from a bad commutator. Heat, oil, carbon accumulation and dirt are the ideal mix to provocate(sic) sparkling when electricity is applied to the motor. Under load, the sparkling will increase and some motors will start smoking..." -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#7
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Wow - nice to see there's still activity on this list, and thanks for
all the replies! KISS is my driver. I'd like to keep it simple, and cheap. Fixing the existing part (if possible) is nearly always my first choice. Besides, I no longer have access to my bench and most of my equipment - all I have here is an old Weller soldering iron, some solder, my favorite Tek scope, and a box full of parts I needed to fix something recently. All the rest is in storage ![]() Anyway, here's a shot of the pedal's guts, with some labels to help clarify. http://i151.photobucket.com/albums/s...y/P4231021.jpg 1. Spring and Linkage. This is pressed downward when the pedal is depressed. 2. Brass Linkage/Contact. This moves to the right via linkage 1 when the pedal is depressed. 3. Copper Contact. This moves to the right and toward the graphite contact on the left end of the Carbon Pile when the pedal is depressed. 4. Carbon Pile. This is a long ceramic tube filled with ~100 graphite discs and a graphite contact on either end. 5. Bypass Contact. When the pedal is fully depressed, the Brass Linkage touches this contact and bypasses the Carbon Pile. Now - here's what I didn't mention previously... I got this thing in pieces at a garage sale, along with the sewing machine. The previous owner had dropped the pedal, cracking the bakelite and spilling its innards all over. He assured me nothing was missing, and when I fiddled with it, it all seemed to fit into place (as shown). BUT, I'm not 100% sure I'm not missing something, and I'm also not 100% sure I have it assembled correctly. The Copper Contact was as shown (nearly straight) when I got it - it doesn't make contact with the Carbon Pile until the Brass Linkage is nearly touching the Bypass Contact. Also, the slot where the Copper Contact and Brass Linkage tie together is held together very tenuously - I'm afraid it's going to fall apart every time I fully-depress the pedal. So what I could use here is an evaluation of the parts and placements - do I have everything? Is it all in the right place? I can't figure any other way to set it up. Any other thoughts? Thanks all! -Pete |
#8
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On 4/23/2009 10:12 AM spake thus:
Anyway, here's a shot of the pedal's guts, with some labels to help clarify. http://i151.photobucket.com/albums/s...y/P4231021.jpg 1. Spring and Linkage. This is pressed downward when the pedal is depressed. 2. Brass Linkage/Contact. This moves to the right via linkage 1 when the pedal is depressed. 3. Copper Contact. This moves to the right and toward the graphite contact on the left end of the Carbon Pile when the pedal is depressed. 4. Carbon Pile. This is a long ceramic tube filled with ~100 graphite discs and a graphite contact on either end. 5. Bypass Contact. When the pedal is fully depressed, the Brass Linkage touches this contact and bypasses the Carbon Pile. Now - here's what I didn't mention previously... I got this thing in pieces at a garage sale, along with the sewing machine. The previous owner had dropped the pedal, cracking the bakelite and spilling its innards all over. He assured me nothing was missing, and when I fiddled with it, it all seemed to fit into place (as shown). BUT, I'm not 100% sure I'm not missing something, and I'm also not 100% sure I have it assembled correctly. The Copper Contact was as shown (nearly straight) when I got it - it doesn't make contact with the Carbon Pile until the Brass Linkage is nearly touching the Bypass Contact. Also, the slot where the Copper Contact and Brass Linkage tie together is held together very tenuously - I'm afraid it's going to fall apart every time I fully-depress the pedal. So what I could use here is an evaluation of the parts and placements - do I have everything? Is it all in the right place? I can't figure any other way to set it up. Any other thoughts? Pretty clear how it works now; as someone described up-thread, the pile of carbon discs gets compressed, reducing their resistance. So obviously this happens when the spring on the left (3) pushes on the metal stud at the left end of the ceramic tube. So apparently the problem is either that the carbon discs aren't making enough contact with each other inside the tube, or are contaminated, or that there's not enough pressure being exerted on the left end of the tube by that spring. Which could mean that either it's not put together correctly, that there's a part missing (though I can't see where), or that something needs bending or some other adjustment to work correctly. -- Save the Planet Kill Yourself - motto of the Church of Euthanasia (http://www.churchofeuthanasia.org/) |
#9
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wrote:
[...] It looks as though you hve got everything in the right place [...] The Copper Contact was as shown (nearly straight) when I got it - it doesn't make contact with the Carbon Pile until the Brass Linkage is nearly touching the Bypass Contact. That's why you aren't getting a gradual start-up, the resistance isn't coming into play until too late in the operating sequence. Also, the slot where the Copper Contact and Brass Linkage tie together is held together very tenuously - I'm afraid it's going to fall apart every time I fully-depress the pedal. Gently curving the 'copper' (more likely phosphor bronze) strip towards the pile would cause it to make contact earlier and would also change the angle of the fork so that it held the brass linkage more positively. Perhaps the fork should be angled more sharply to make sure it is well hooked into the strip (be careful not to crease the metal and snap it). Have you checked the carbon discs to make sure that some of them aren't shattered - or some might be missing?. That would make the pile too short to touch the 'copper' strip properly. -- ~ Adrian Tuddenham ~ (Remove the ".invalid"s and add ".co.uk" to reply) www.poppyrecords.co.uk |
#10
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On Thu, 23 Apr 2009 10:12:49 -0700 (PDT), wrote:
3. Copper Contact. This moves to the right and toward the graphite contact on the left end of the Carbon Pile when the pedal is depressed. I would try adding some (conducting) padding at the centre of the bronze spring (around the "3" area) to make contact with the carbon. Is it possible a copper/brass disc is missing around there? -- Geo |
#11
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On Wednesday, April 22, 2009 3:17:37 PM UTC-5, wrote:
Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete Just fixed one of these and found this ancient thread. Thought I might put this up for people finding this thread. The carbon discs get burned, so go through the stack and discard any that have broken, then take a very fine sand paper (600 grit)and lightly sand both faces of each disc. Make up the space for any discards or accidentally broken while sanding discs with some small washers. It is important that the gap be filled with something strudy, not foil or steel wool. We don't want springinees to the stack. The discs are poor conductors and need to pushed very hard together to decrease the resistance, therefore increasing the motor speed. You don't want the little metal nub at the end of the tube that engages the arm to be mobile. Do not bend the leaf spring unless you think it has been changed, it's tension is set to not break the discs. Good luck. |
#12
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On 24/10/2014 22:31, just fixed it wrote:
On Wednesday, April 22, 2009 3:17:37 PM UTC-5, wrote: Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete Just fixed one of these and found this ancient thread. Thought I might put this up for people finding this thread. The carbon discs get burned, so go through the stack and discard any that have broken, then take a very fine sand paper (600 grit)and lightly sand both faces of each disc. Make up the space for any discards or accidentally broken while sanding discs with some small washers. It is important that the gap be filled with something strudy, not foil or steel wool. We don't want springinees to the stack. The discs are poor conductors and need to pushed very hard together to decrease the resistance, therefore increasing the motor speed. You don't want the little metal nub at the end of the tube that engages the arm to be mobile. Do not bend the leaf spring unless you think it has been changed, it's tension is set to not break the discs. Good luck. Good on you. I went to an open day with these people http://www.tfsr.org/ they have a room , with expert retirees , repairing hand and powered sewing machines as well as all the carpentry and engineering tool repair/reconditioning |
#13
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On 25/10/2014 14:09, N_Cook wrote:
On 24/10/2014 22:31, just fixed it wrote: On Wednesday, April 22, 2009 3:17:37 PM UTC-5, wrote: Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete Just fixed one of these and found this ancient thread. Thought I might put this up for people finding this thread. The carbon discs get burned, so go through the stack and discard any that have broken, then take a very fine sand paper (600 grit)and lightly sand both faces of each disc. Make up the space for any discards or accidentally broken while sanding discs with some small washers. It is important that the gap be filled with something strudy, not foil or steel wool. We don't want springinees to the stack. The discs are poor conductors and need to pushed very hard together to decrease the resistance, therefore increasing the motor speed. You don't want the little metal nub at the end of the tube that engages the arm to be mobile. Do not bend the leaf spring unless you think it has been changed, it's tension is set to not break the discs. Good luck. Good on you. I went to an open day with these people http://www.tfsr.org/ they have a room , with expert retirees , repairing hand and powered sewing machines as well as all the carpentry and engineering tool repair/reconditioning just noticed this resource on their site http://www.tfsr.org/publications/tec...achine_manual/ |
#14
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On Fri, 24 Oct 2014 14:31:21 -0700 (PDT), just fixed it
wrote: Just fixed one of these and found this ancient thread. Thought I might put = this up for people finding this thread. The carbon discs get burned, so go = through the stack and discard any that have broken, then take a very fine s= and paper (600 grit)and lightly sand both faces of each disc. Make up the s= pace for any discards or accidentally broken while sanding discs with some = small washers. It is important that the gap be filled with something strudy= , not foil or steel wool. We don't want springinees to the stack. The discs= are poor conductors and need to pushed very hard together to decrease the = resistance, therefore increasing the motor speed. You don't want the little= metal nub at the end of the tube that engages the arm to be mobile. Do not= bend the leaf spring unless you think it has been changed, it's tension is= set to not break the discs. Good luck. Very interesting. I started with my mother's treadle machine, and I have a barely "portable" from about 1950, but I mostly use a White rotary that 35 years ago my girlfriend's roommate found on the sidewalk being thrown away in NYC and managed to squeeze into the back of her VW bug, even with the table. She was gay and said that I was the only guy she liked at all. But I'm posting because, in my search for zig-zag, I came across a Singer that depended on vacuum to control the speed. The person who gave it to me had lost the foot pedal, but I could test it by putting a hose on the connector and sucking on it. The harder I sucked the faster it went!!! Eventually I found a used pedal that wasn't too much money. I wonder if that uses the same carbon discs. I sort of doubt it, but to find out I'd have to take apart the machine, not just the pedal. |
#15
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On Wednesday, April 22, 2009 4:17:37 PM UTC-4, wrote:
Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete My wife has a 35 year old Singer with the same type of speed control. Hers developed the same problem several years ago and increasing the disc tension slightly fixed the problem. If yours is unserviceable how about an old time sewing machine store? We have a guy around here that's been in the vacuum cleaner business since Columbus came over. He has a supply of old vacuums from day one. Perhaps you might be able to find someone like that who may have one of these just collecting dust. I would have to agree with Jeff about not using a PWM type of speed control. For the same reason I never put one on my 1953 Lionel train set. Lenny |
#16
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On 25/10/2014 8:31 AM, just fixed it wrote:
On Wednesday, April 22, 2009 3:17:37 PM UTC-5, wrote: Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete Just fixed one of these and found this ancient thread. Thought I might put this up for people finding this thread. The carbon discs get burned, so go through the stack and discard any that have broken, then take a very fine sand paper (600 grit)and lightly sand both faces of each disc. Make up the space for any discards or accidentally broken while sanding discs with some small washers. It is important that the gap be filled with something strudy, not foil or steel wool. We don't want springinees to the stack. The discs are poor conductors and need to pushed very hard together to decrease the resistance, therefore increasing the motor speed. You don't want the little metal nub at the end of the tube that engages the arm to be mobile. Do not bend the leaf spring unless you think it has been changed, it's tension is set to not break the discs. Good luck. **Yep. My SWMBO thinks I am a hero. I fixed her foot control more than a decade ago, using your method. It still works fine. More recently, part of the system which feeds the cloth was dodgy. I stipped it down and fixed that too. Bugger me, those damned things are complicated. -- Trevor Wilson www.rageaudio.com.au |
#17
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On 09/11/2014 03:52, Trevor Wilson wrote:
On 25/10/2014 8:31 AM, just fixed it wrote: On Wednesday, April 22, 2009 3:17:37 PM UTC-5, wrote: Anyone know how these old singer foot pedals work? There's not much to this thing, but I can't for the life of me figure out how it's supposed to work! The one I have contains a long ceramic tube filled with a stack or maybe 100 graphite disks. One end connects to the sewing machine motor (I assume), and at the other end there's a contact that's brought closer to and eventually touching the contact on the end of the tube as the foot pedal is depressed. The foot pedal was dropped and I'm trying to repair it, but so far I can't get any variable speed out of it - I get either off (when the contact isn't touching the end of the graphite-disc-tube) or ON-HIGH when the contact touches the end of the graphite-disc-tube. Sorry for the miserable description - it's been about a month since I had the thing apart - just figured I'd post here to see if anyone had any suggestions. thanks! -Pete Just fixed one of these and found this ancient thread. Thought I might put this up for people finding this thread. The carbon discs get burned, so go through the stack and discard any that have broken, then take a very fine sand paper (600 grit)and lightly sand both faces of each disc. Make up the space for any discards or accidentally broken while sanding discs with some small washers. It is important that the gap be filled with something strudy, not foil or steel wool. We don't want springinees to the stack. The discs are poor conductors and need to pushed very hard together to decrease the resistance, therefore increasing the motor speed. You don't want the little metal nub at the end of the tube that engages the arm to be mobile. Do not bend the leaf spring unless you think it has been changed, it's tension is set to not break the discs. Good luck. **Yep. My SWMBO thinks I am a hero. I fixed her foot control more than a decade ago, using your method. It still works fine. More recently, part of the system which feeds the cloth was dodgy. I stipped it down and fixed that too. Bugger me, those damned things are complicated. Is the resistance variation due to surface effects rather than bulk effect. I dug out a couple of ancient boxes , 1930s?,of some locally made "Health Ray Infra-Red Carbons" from when you could say on the box that such rays cured everything except cancer and no namby-pamby H&S concerns about covering the heated rods to stop toasting forks or whatever. Anyway (before mm days but) about 8mm diameter and 150 mm long. The minimum resistance over that length about 0.7 ohms but is highly critical of how pointy and pressured the DVM probe tips are. |
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