Glitchy Enertec 7150 ( Solartron / Schlumberger ) - Page 1
Forum section: electronics / repair

author: jtu
author_rank: Unknown
timestamp: August 24, 2017, 08:20:01 pm
content: Hi,I've got my hands on one a few days ago. It is not working stable. It can be working for hours one day, but the other day it has one of the 3 behaviours:1. Upon turning it on it continuously clicks relays very fast, buzzing actually. "Fail 1" on the display.2. Upon turning it on it shows "Fail 1" on the display. No relay sounds.3. But most often it seem to be resetting itself repeatedly in a matter of seconds to minutes. Sequence of action on the display is: OL, Fail 1, reset, normal. Relays clicking slowly meanwhile.I have checked power rails, those are within specs and seem stable over time. I have not logged voltages, but I have measured on multiple occasions either cold or warm, good or failed state.IC103 clock is stable.I've got impression that it generates some signal on the HI input which causes overload or autorange fail. It can be vice versa of course. Autorange works normally when it is in a "good mood".I have seen the following. Usually voltage fluctuates a bit (nothing connected). OL happens when the fluctuations go from last 2 digits to next one(s). I tried to catch it on the scope, it goes up to 0.2-0.7V when that happens.I have read posts here about this model. I have not found any with similar symptoms. Elsewere out there too.I would like to continue to debug it, but have not enough knowledge. Any advice, suggestions, ideas?Schematicshttp://www.ko4bb.com/getsimple/index.php?id=download&file=06_Misc_Test_Equipment/Solartron/Solartron_7150/Solartron_7150_Maintenance_Manual.pdf. I have newer model from the two described, first power schematic from two.Veiksmi,J?nis

author: jtu
author_rank: Unknown
timestamp: August 25, 2017, 07:59:57 am
content: Today I put some attention to data transfer between floating analogue and earthy logic parts. This was because I read here that optocouplers might be the culprit.Logic -> analogue seem almost normal TTL levels, but the opposite direction seems weird to me. See pics. It's almost like something is pulling the line down by more than 2V. Is this normal behaviour?

author: Armadillo
author_rank: Super Contributor
timestamp: August 25, 2017, 09:21:26 am
content: Check the reference voltage at;Measure;R14 with respect to the anode of D20, can you get 13v or 14v [either Leg of R14].

author: jtu
author_rank: Unknown
timestamp: August 25, 2017, 04:11:49 pm
content: Thanks for the clue!R14 measures 12.9V and 13.9V (I'm dropping last digit of my multimeter, it is no precision device).

author: Armadillo
author_rank: Super Contributor
timestamp: August 25, 2017, 08:04:56 pm
content: Does the meter measures input correctly?Example apply a known voltage to the input terminal, what voltage is read out?Apply a known resistance to the input, what voltage is read out?

author: jtu
author_rank: Unknown
timestamp: August 25, 2017, 09:07:52 pm
content: Yes, it measures voltages and resistance correctly when it is in "a good mood". Accuracy might be questionable, but it compares with other meters.

author: Armadillo
author_rank: Super Contributor
timestamp: August 25, 2017, 09:57:39 pm
content: Quote from: jtu on August 25, 2017, 09:07:52 pmResolder all dull solder joints, check connectors, WD40 contact cleaner on all mechanical switches and contact surfaces.If the meter is expensive, I would begin to change all the coto relays or parts therewith.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: August 26, 2017, 07:31:38 pm
content: QuoteThis is absolutely normal start up feature - "relays contacts refreashing"."Fail 1" has nothing to do with the voltage reference, COTO relays or anything in the analog signal path. The most common cause of Fail 1 is optocouplers LED degradation.

author: Armadillo
author_rank: Super Contributor
timestamp: August 26, 2017, 08:10:03 pm
content: Quote from: Mickle T. on August 26, 2017, 07:31:38 pmHey Dude, did you not see the strong optocoupler pulses in the attached oscilloscope traces attached above?Since you are so sure about yourself, then why don't you tell us how do you propose to test the optocoupler degradation to justify your assertion.

author: jtu
author_rank: Unknown
timestamp: August 26, 2017, 10:20:03 pm
content: Took it apart today. Looked for solder problems.Noticed that somebody has already done a repair on this. IC15, IC5511, C4 has been replaced. Soldering job did not look convincing (some pins were not wetted on the other side). Resoldered those. No other visible soldering problems.Cleaned it a bit.Same behaviour. Thinking about the next step now...Meanwhile, take a look at the pictures

author: jtu
author_rank: Unknown
timestamp: August 26, 2017, 10:25:48 pm
content: Noticed that Schaffner filter makes noise sometimes. I should replace it.But it would be good to find the problem first.

author: jtu
author_rank: Unknown
timestamp: August 26, 2017, 10:29:04 pm
content: Quote from: Mickle T. on August 26, 2017, 07:31:38 pmNot a big problem to replace optocouplers. It would be good to confirm it first somehow...

author: Mickle T.
author_rank: Frequent Contributor
timestamp: August 27, 2017, 07:25:21 am
content: Quote from: Armadillo on August 26, 2017, 08:10:03 pmHey Dude, It's not my assertion. Did you not see the service manual?

author: Armadillo
author_rank: Super Contributor
timestamp: August 27, 2017, 09:15:27 am
content: Quote from: Mickle T. on August 27, 2017, 07:25:21 amThe optocoupler was "CHECKED" by OP and if it failed, it won't be doing any measurement reading and the "fail 1" will be shown upon power on and remain shown, won't you say, howeverthe texts also said to "Check the connecting wires and plugs", which you conveniently left out.So, would you propose how to test your assertion that is it "optocoupler DEGRADATION despite the oscilloscope traces shown to you?From the OP description, fail 1 appears somewhat cyclic and furthermore coupled with relay cycling, so I reckon the "possibility" of relay stiction or intermittent failures of contacts which is a common failure mode of such reed relays causing the microcontroller to time-out and failed on communication intermittently. It could be a degradation of the optocoupler but the strong pulses have been shown to written it off. What do you think about the oscilloscope traces shown to you.You are absolute with what you "read". So would you propose the tests to complete this repair other than what you "read". And do comment on the traces in your reply.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 27, 2017, 11:22:47 am
content: I have seen LEDs fail in a kind of intermittent way, likely due to a loose bond wire. It is possible that optocoupler can show a similar type of failure - working sometimes and not working if at a different temperature / board stress. So even if the scope measures Ok there might be still a failure in the Opto-couplers. The DMM seems to work sometimes. The failure is of an intermittent type, like a bad solder joint, connector or similar and according to the manual in the path of the optocouplers.Compared to the relays optocouplers are cheap and easy to replace.The relays used are difficult to get and soldering it somewhat critical as it is in the low leakage area - so the relays are among the last parts to replace, unless one knows for sure they are bad.

author: Mickle T.
author_rank: Frequent Contributor
timestamp: August 27, 2017, 11:41:50 am
content: Among many of the repaired DMMs, I has a Solartron 7150+, 7081 and Datron 1071 with the same (or similar) problem. 7081 was very old (revision F) and has a two failed optocouplers: 1/4 of ILQ74 in the analog section and one 6N136 in the floating link (similar to 7150+). The quick and dirty o/c checking is very simple: decreasing a current limiting resistor, e.g. by 50%.

author: Armadillo
author_rank: Super Contributor
timestamp: August 27, 2017, 12:23:44 pm
content: Quote from: Kleinstein on August 27, 2017, 11:22:47 amBased on your cheaper economical theory hypothesized with element of stress and temperature variants might be a convenient way out, but a way out, nevertheless. No arguing about it.Replace and change the cheaper components is the way of repair, so to speak.But since you agreed the scope measures OK, but still chance the opto-couplers failure. I would add that, technically speaking, one should also understand how the pulses are generated in the "integrator" in the first place that could also mask as a fail 1.With that said and judging from the age of the instrument and the retrospective failure and repair of the optocoupler, I should say, experience do count and so be it.

author: Armadillo
author_rank: Super Contributor
timestamp: August 27, 2017, 12:48:07 pm
content: Quote from: Mickle T. on August 27, 2017, 11:41:50 amIts quite an interesting dirty method actually, except I don't understand if you want to increase If or decease it. Can you elaborate further.But on the hindsight, this method definitely warrant a lot of failed optocoupler, nevertheless. It that a standard practice?

author: 2N3055
author_rank: Super Contributor
timestamp: August 27, 2017, 02:55:43 pm
content: Quote from: Armadillo on August 27, 2017, 12:48:07 pmWith optocouplers, with age CTR of coupler starts to degrade.. Mostly LED degrade with their light efficiency.So you increase LED current by some margin and check if that will cleanup signal on other side...You can do that by temporarily connecting a resistor in parallel with existing LED current limit resistor and see if it helps..If it does, CTR od optocoupler is getting out of specs marginally, just enough for circuit to intermittently stop functioning reliably, but not fail completely so it is obvious...But it is ready for replacement..

author: SeanB
author_rank: Super Contributor
timestamp: August 27, 2017, 03:06:42 pm
content: The dropping resistor trick was very common on HP printers where the opto switches lose coupling ratio with time, so increasing current will gain a good extension of life.

author: Armadillo
author_rank: Super Contributor
timestamp: August 27, 2017, 05:22:55 pm
content: At least we have 3 different versions of the poor-man's trick, I mean the poor man days without an oscilloscope.Well, facing with the OP measurement of strong oscilloscope traces with a pk to pk swing exceeding 5volts,do you think that the Pk to Pk swing looks like a problem of CTR Opto degradation to you?What's the threshold of standard TTL logic or CMOS logic?We heard 3 version of it.One say O/C for open circuit, [don't understand what's he talking about?]One say intermittent, on the basis that parallel the resistor will alleviate the problem, if it doesn't then its marginal opto degradation. [not positive, may miss other causes of failure].One say life extension [I agree, depends on how hard the Opto LED was driven, depend on the opto collector load resistor value also].But I am not against the proposal to doubt the opto and change it on the basis of the age of the instrument.

author: 2N3055
author_rank: Super Contributor
timestamp: August 27, 2017, 09:25:18 pm
content: Those scope traces doesn't look like anything to me.. First, they look like they were done with AC coupling, and you can see baseline of signal moving as capacitor is charging...Average DC component of square wave that is not 50% duty cycle is not 0V...So it looks like it has negative component and goes below 0 volts...Second, timebase is too long, can't see edges at all... If CTR of optocouplers is marginal, you might get distorted edges, and also unstable jitter on timing of edges and shortened pulses... Timebase is such on those snapshots that you can't really see any detail..So while voltage swing seem ok, it is far from saying that everything is OK...Like Mickle said, he should check both Rx and Tx, on optocouplers and after TTL buffers.Communication could very well be TTL level RS232, it might even be possible to decode traffic...And since somebody was already inside, check whether jumper SP1 is shorted as it should be.....

author: Armadillo
author_rank: Super Contributor
timestamp: August 27, 2017, 11:00:09 pm
content: Quote from: 2N3055 on August 27, 2017, 09:25:18 pmThat is because there is a floating Board and a Earthly Board, and the reason why optocouplers are used for intercomm. They don't call it floating for no reason. On the floating board, the common is not better defined, so irregardless of how he hooked the probe, as long as there is a delta V. forward voltage onto the LED of the optocouplers, it will transmit those pulses..Quote from: 2N3055 on August 27, 2017, 09:25:18 pmFrankly, its appalling of what you are saying about those edges but I think you are trying to say the rise/fall time of the pulses that is deemed acceptable. For the fun of it, what's the value?Quote from: 2N3055 on August 27, 2017, 09:25:18 pmHe should, might as well.

author: jtu
author_rank: Unknown
timestamp: August 28, 2017, 09:31:30 pm
content: Quote from: Mickle T. on August 27, 2017, 11:41:50 amThanks for the advice!I tried it today.First, I made a test rig, see picSecond, I tried to play with resitances.But I must say that the meter had "a very good day" today. It worked without problem for couple hours before I started on it. I got Fail 1 only three times today in total around 5h time. First, before I attached resitances, I poked RX and TX lines on both sides of the optocouplers with an oscilloscope proble. Fail 1 happened when I touched pin 3 IC519, diode part of the optocoupler responsible for the direction earthy logic -> floating analogue. Later, out of the blue, no action from me at that moment. That was in between and after my play with test resistances.No action to watch, no conlusions for today.Just a feeling that I should replace optocouplers anyway, it's cheap and simple. I'm going to replace mains filter because I don't like noisy parts which should be silent anyway, that's much more expensive.I'm leaving it overnight measuring cheap 5V USB supply.PS Btw, have anybody stumbled on 7150 service manual with Fail 1 explanation? I can see the explanation in the 7150+ manual, but not in 7150's. I still think it is the same, because that part of the schematic seem identical.

author: jtu
author_rank: Unknown
timestamp: August 28, 2017, 10:16:51 pm
content: Quote from: 2N3055 on August 27, 2017, 09:25:18 pmSorry, my bad, it really was AC couplingI just got this scope, this is actually the first project with it. I'm still used to my old analogue...Much to learn.Attaching a few more pics, DC coupling this time. Measured on pin 6 (collector) of the optocouplers. 1st channel (yellow) is floating analogue -> earthy logic direction.But it's getting too late for me to continue today.

author: jtu
author_rank: Unknown
timestamp: August 28, 2017, 10:20:42 pm
content: PS Scope earth was attached to floating.

author: jtu
author_rank: Unknown
timestamp: August 31, 2017, 08:52:49 am
content: Now it has been running almost non stop since my last post. What I can see while I'm not away - it does Fail 1 thingy much less with reduced resistors for optocouplers' diodes. Of course, it can be just a coincidence, "a mood". But it definitely does not go against optocouplers hypothesis.Another question. I poked RX & TX lines further. What I can see is that TX (from the analog) signal is a bit noisy on logic side when it is 1. You can see it in the scope pics I posted before. This noisiness exceeds NAND gate (IC515C). The RX line is not noisy. The power rail is not noisy. Noisiness does not depend on which ground I use for the scope. Can the gate be noisy? Can something beyond the gate be noisy? If yes, I'd like to replace the gate, I could order parts in one order with optocouplers and filter.

author: 2N3055
author_rank: Super Contributor
timestamp: August 31, 2017, 09:37:41 am
content: Quote from: jtu on August 28, 2017, 10:20:42 pmJust a reminder, you must measure against LOCAL ground. On analog board with analog board ground, on floating board, floating board ground.Boards are isolated from each other, any current and voltage you measure will be parasitic and not good.

author: jtu
author_rank: Unknown
timestamp: August 31, 2017, 02:10:51 pm
content: Quote from: jtu on August 31, 2017, 08:52:49 amSorry, I have mixed up some things definitelyIC515 is on the input of RX line... Will recheck the noisiness later today.

author: Twoflower
author_rank: Frequent Contributor
timestamp: August 31, 2017, 04:58:22 pm
content: Nothing related to the problem. But you might consider to make sure that the EPROM-Sticker is fixed. It would be bad if the EPROM start to lose its data.

author: jtu
author_rank: Unknown
timestamp: August 31, 2017, 05:39:09 pm
content: Quote from: Twoflower on August 31, 2017, 04:58:22 pmYes, sticker is not fixed, it has curled. I tried to put it back a few times by simply pushing it down, but it is obvious the glue has died. Any recommendations about how?

author: Twoflower
author_rank: Frequent Contributor
timestamp: August 31, 2017, 06:03:41 pm
content: I would probably use some good sticking insulation tape to replace the sticker. Eventually with a piece aluminium foil at the area of the window to be sure no UV is passing through the tape. And write the data of the sticker on the tape.Or just use some glue to glue the sticker back on. But do not super glue as this could have some nasty side-effects to the device.In the Old Days(TM) the 5 1/4" Floppy Discs came with a sheet of write protection stickers. Some were metallized. That would be a nice replacement.

author: jtu
author_rank: Unknown
timestamp: August 31, 2017, 07:15:27 pm
content: Quote from: Twoflower on August 31, 2017, 06:03:41 pmYeah, I have used thoseUnfortunately I have none 5 1/4" left. Just a few 3.5"

author: jtu
author_rank: Unknown
timestamp: September 05, 2017, 07:07:05 pm
content: Sorry, my "later today" or "tomorrow" tends to be overoptimistic...Finally, I have poked through RX / TX lines with a scope. Two findings:* I can confirm, that TX line 1 (or "high") is a little bit noisy "after" the optocoupler. After meaning, on logic side. Not much, but still.* I was surprised to see data line signalI start to doubt if I know how to use the scope againI'm attaching two pics here showing abovementioned. Anybody wants to go through all the points I poked? All the pics herehttps://goo.gl/photos/kj3hLedzVtKwgBf89and the table herehttps://docs.google.com/spreadsheets/d/10az8yuaGpXJiQ2TQBqEZ0myO_NRuVFA45nJF3TZ0CoY/edit?usp=sharingAnother observation: I removed extra resistors and Fail 1 seem to happen more often again. No data collected, just a feeling.Anyway, optocouplers and filter ordered.PS I tried to buy parts from RSDelivers (for the first time). It was a big fail. They lost my order, but took the money. And told me they do not deliver (under certain circumstances, whatever that means) to Latvia after we started to investigate. So, refund it is. Ordered from DigiKey just a minute ago.

author: jtu
author_rank: Unknown
timestamp: September 23, 2017, 02:59:57 pm
content: I got optocouplers yesterday.UPS in my country Latvia really sucks. They did USA->LV in 3 days and then 15 days to get it to my door.

author: jtu
author_rank: Unknown
timestamp: September 23, 2017, 03:31:22 pm
content: I have replaced the Shaffner filter. A few notes:* The 1M resistor is shown on the schematicwithinthe filter. In real life the resistor is soldered outside the filter on the contacts. Schaffner filter does not contain the resistor, neither old nor the new one.* The old one was covered with dregs of some white matter. See pic. What was it I wonder? Does not seem like a factory made.* Plastic legs holding the old one in place broke during dismount. Crumbled. Because of age, I assume. This is controversial to the previous finding.* Schematic says fuses should be 100mA. Real life ones were T0.63.* The funny thing was to discover that the old filterdid notmake noiseIt was the screws that hold the transformer and the logic board to the enclosure! They vibrated when unscrewed and left in the sockets.Finally. Changing the filter does not seem to have had any effect on the meter.

author: jtu
author_rank: Unknown
timestamp: September 23, 2017, 03:38:59 pm
content: I have replaced the TX line optocoupler. Could have done both, but decided to do it one by one in order to catch the guilty one.I have left the meter on, measuring a resistance, for the test period. Previously it has never survived overnight without resetting itself. It has not done it for 3 hours while I'm writing this post.Previously it kept changing last 2, sometimes 3 positions of the measurement. Now it stays within a few digits. This gives hope

author: jtu
author_rank: Unknown
timestamp: September 23, 2017, 04:05:43 pm
content: Btw, replacing the optocoupler did not eliminate small noise on the TX line I mentioned before.

author: jtu
author_rank: Unknown
timestamp: September 23, 2017, 04:10:43 pm
content: I found out something new before doing abovementioned. IC305, the voltage regulator, gives -24.6V. I think it is as previously. But the IC307 in the cal mode gives -23.6V. Should be -25V, I should revisit my previous records.

author: jtu
author_rank: Unknown
timestamp: September 24, 2017, 06:14:18 pm
content: It has managed ~30 hours without resetting, still going.Changing the filter might have been a good idea. By touch it feels that power supply makes less heat now.

author: jtu
author_rank: Unknown
timestamp: September 28, 2017, 06:57:33 pm
content: Ok, found it with Fail 1 again. It happened overnight between 54 and 64 hours of working.Must be the other optocoupler.Changed it and left the meter on. Let's see now.

author: jtu
author_rank: Unknown
timestamp: October 06, 2017, 06:42:13 pm
content: 8 days of non-stop without the Fail 1. To me it is pretty conclusive.Next steps:* I'm going to change display lighting diodes and fix some mechanic defects.* Need to fix that sticker.* Ordered cheap-ass GP-IB / USB interface from ebay, waiting for it to test.* I will look for calibration service in Latvia as a last step.

author: 2N3055
author_rank: Super Contributor
timestamp: October 06, 2017, 06:52:12 pm
content: Enjoy using your "new" meter

author: jtu
author_rank: Unknown
timestamp: October 08, 2017, 09:24:22 am
content: I have replaced LEDs, reglued the flapping aluminium plate on the front panel, cleaned it a bit.Before and after pics.

author: jtu
author_rank: Unknown
timestamp: October 26, 2017, 07:57:31 pm
content: Just received my GPIB-USB interface. Looking forward to when I'll have time to test it.Normal thing to do would be to install software coming with it in a virtual Windows machine, right? I'm still going to look around if there is any solution to run directly on Mac. Any suggestions?A little rant.I bought it off eBay from China of course. Agilent 82357B likethis. Less than 100 Eur delivered including tax.I know, risks of defective, counterfeit, no warranty, etc. I know what I'm doing. Btw, looks original enough to me. Good enough for the hobby anyway.But then, look at the "original", e.g.hereat Farnell. 700+ Eur including tax and delivery. This is crazy difference!Ok, I could get some counterfeit sh.t. But let's assume it's not. Let's assume it is true that some factory worker got paid his/her salary partly in those devices and has to sell them to get money. That is existing practice, there btw. Is really all the development, branding, warranties, insurances, maybe even better boxing and safer transportation really worth 7-10 times product production value? Ok, this is very specific product. And who needs GPIB nowadaysBut still, this is crazy!Peace, read Dave'sThe Economics Of Selling Your Hardware Project

author: jtu
author_rank: Unknown
timestamp: January 12, 2018, 08:18:51 pm
content: I still have not managed to set up the GPIB...But I'm posting because I got weird behaviour of the meter. Sometimes upon turning it on it shows OL and sets to FAIL 1 again... But after trying several times I allways have got it working and stable (for days). Wondering what could be the cause... What could cause overload on data line between floating and earthed boards?

author: jtu
author_rank: Unknown
timestamp: January 15, 2018, 11:01:32 am
content: PS One thing I have noticed. Seem that problem occurs more often when leads are attached to the device. Test leads or grounding wire. I wonder if that might point to something? External interference sensitivy changed? How?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 16, 2018, 04:06:11 pm
content: The external leads could act as an antenna to catch up some RF crap. Modern DMMs often have a kind of common mode filter for the terminals - something like 2 or 3 turns through a ferrite ring. Even just a clamp on ferrite might have a similar effect, e.g. if the cable is to short.

author: jtu
author_rank: Unknown
timestamp: February 04, 2018, 03:06:43 am
content: Is it only RF?I noticed that there are fluctuations of the reading when I simply put my arm close to the inputs.Could it be mains? Would ferite rings help with 50Hz too?

author: jtu
author_rank: Unknown
timestamp: March 08, 2018, 12:10:52 pm
content: I got my ferrites delivered today. Will try, over this weekend hopefully.

author: jtu
author_rank: Unknown
timestamp: March 12, 2018, 06:25:59 pm
content: Ok, it was couple hours of fun adding the ferritesNo improvement thou.You can take a look at some before/after picshere.I had a hypothesis that maybe the problem occurs only during the warming up. Especially because unit is stable at least for days after it gets stable. But no, warming up did not eliminate the procedure of turning it on/off for several (like ~10) times before it gets stable.I'm in need of the next hypothesis.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 13, 2018, 01:02:37 pm
content: Individual ferrites to all inputs are unusual. The more normal type is having a single (maybe a second for rear terminals) large ferrite ring and all the wired going through. This would act as a common mode choke only. The individual ferrites could cause a little trouble in the current ranges in some applications. The individual chokes will still dampen common mode RF. So the more common common mode choke would not give a much larger effect, just less side effect on the current measurement.For the problem when turning on, one possible problem can be bistable relays. There are a few ways to handle the initial state - some methods may not be that reliable. The normal way would be switching them to the desired state - which is a good solution (though noisy), if there is enough delay for the power to stabilize.

author: jtu
author_rank: Unknown
timestamp: March 18, 2018, 02:51:36 pm
content: Quote from: Kleinstein on March 13, 2018, 01:02:37 pmIn the beginning of this discussion thread you kind of fought against relays as a cause for "Fail 1"The symptom again is meter showing "Fail 1", just under another circumstances. But let's discuss it. Two questions:- If we assume the meter is diagnosing the cause of the problem correctly, how bistable relays can cause data transmission line issue? The problem is repeatable this time, meaning relays do the same thing. What thing could it be?- I don't get what you mean as a remedy in the last sentence. I'd google around, but could you give a bit more?

author: Mickle T.
author_rank: Frequent Contributor
timestamp: March 18, 2018, 03:09:09 pm
content: I don't see any bistable relay in the 7150.

author: jtu
author_rank: Unknown
timestamp: March 27, 2018, 09:22:23 am
content: Just short update about interesting behaviour. This morning I got the meter working without restarting it several times. The differences from my usual power-on behaviour were two:a) There was a DUT connected before power on. It was my DYI resistance standard connected via Kelvin leads. I kind of think I had done something like this previously, but can't really remember.b) I did not use the meter's power on switch. I have another switch in the power extender. This type of power on I do not remember myself doing at any time.This is in no way conclusive, I'll try to repeat this later.

author: jtu
author_rank: Unknown
timestamp: April 01, 2018, 08:51:59 am
content: No, this behaviour is not repeatable. That would be too easy, wouldn't it?

author: we
author_rank: Newbie
timestamp: August 30, 2021, 12:56:59 pm
content: to fix fail 1 I replaced C301 (2200uF/16V)