Keithley 2001 defective relay - Page 1
Forum section: electronics / testgear

author: exit_failure
author_rank: Regular Contributor
timestamp: December 20, 2021, 07:16:31 pm
content: Hello,I recently got a hold of a Keithly 2001 DMM. The meter react to button presses as expected but makes a noise shortly after turning on which sound like one of the relays is being switched very quickly. If the meter hasn’t been turned on for a while, the noise takes a couple of seconds to appear. If the meter has been turned on and off recently the noise can be heard immediately when the unit is turned on again.The noise seems to be coming from one of the relays:I’ve also attached a zip-file with a video in which the noise can be heard. The relay in question is a MATSUHITA (PANASONIC?) AROMAT DK1A1BE-6V.I have three questions:What does the 'E' in 'DK1A1BE' mean?The relay doesn’t seem to be produced any more. What would be a good stand-in?Could be something else or at least additional things wrong with the meter? Could the fast-switching relay just be a symptom for something else? What should I look for?Many thanks in advance.PS:How do a inline an attached image properly?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 21, 2021, 04:52:41 am
content: Some meter do have clicking relays when they start, the input Kinda place itself for the needed measurements functions ... DO the measurements work okay ?? DO you have some problems with the meter ?But some K2001 user(s) can or could answer you, be patientIf you need themhttps://www.ebay.com/itm/353249936558It depend how the relays is made Ex: some of them are reed switches, some are mechanical contacts ... you could have some wear over time, oxidation in some case with unsealed casings ...For an example, at my work some relays develop an non infinite conductance between the contacts pins, meaning it affect one detection circuit on a pcb, if you measure the normally open contacts we have some 20 to 30 mega ohms of impedance, not infinite as we should havePop a new one (tested) and it's okay

author: exit_failure
author_rank: Regular Contributor
timestamp: December 22, 2021, 03:14:22 am
content: Quote from: coromonadalix on December 21, 2021, 04:52:41 amIf you listen to the noise in the video, you'll notice that this is not the normal few clicks on instrument startup but a permanent noise sounding like dozens of switching operations per seconds as a continuous tone.Quote from: coromonadalix on December 21, 2021, 04:52:41 amI already saw this exact offer. Unfortunately they're almost 30€ for one incl. shipping to Germany.Quote from: coromonadalix on December 21, 2021, 04:52:41 amWhat I meant was what problems there might be in the surrounding circuitry possibly being able to damage a potential replacement relay.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 22, 2021, 03:31:21 pm
content: No problemoI think some partial reversed schematic work have been done on the 2000 and 2001Or some K2001 user could help you with the input control logic / switching ??

author: Kleinstein
author_rank: Super Contributor
timestamp: December 22, 2021, 05:22:40 pm
content: The should be some schematics available one xdevs: both a reverse engeniered and some "official" Keithley parts.With latching relays there is often some switching going on after turn on to bring them to a defined state. In some cases there can also be a power on self test the operates some relays.From the schematics it looks like the K501 relay is for the AC volts input. So there is little chance is would get damaged by the control side (unless the 5 V supply is way too high, witch would cause way more damage).The K2001 meter has an odd way to switch between 115 and 220 V mode with a relay. This may also react with a delay and there a fault in the ciruit could damage the relay and maybe more from repeated switching between the 2 cases.

author: commongrounder
author_rank: Frequent Contributor
timestamp: December 22, 2021, 06:11:06 pm
content: I haven’t seen this mentioned yet, but when I hear a relay chattering, the first thing I look at is excessive ripple on the coil voltage supply line. It could be as simple as a bad capacitor, and the relay itself might actually be okay. Just a thought.

author: exit_failure
author_rank: Regular Contributor
timestamp: February 20, 2022, 11:54:01 am
content: So it wasn't the relay after all.Instead I noticed some damage around the caps C114 and C115. after removing the capacitors and cleaning up the board I saw that the electrolytics had leaked and that the electrolyte had eaten a veritable crater into the board. I desoldered all the caps in the instrument and saw that ALL of the Nichicon UVZ series caps were leaky on the bottom where the lead penetrates the case. fortunately none of the other have leaked that badly. I just ordered a set of replacement caps. let's see, if I can get the meter working again.

author: exit_failure
author_rank: Regular Contributor
timestamp: February 20, 2022, 12:32:21 pm
content: I almost forgot: In the photo in the previous post you can see that the rectifier CR106 must have gotten really hot as well. I still measures good but I'll replace it just to be on the safe side. Since some of the tracks have been destroyed and some pads have been lifted by the heat and the electrolyte, I'll have to run some jumper wires as well.