What is an idea behind OVP in Korad PSU? - Page 1
Forum section: electronics / general

author: firehacker
author_rank: Contributor
timestamp: January 13, 2025, 10:56:28 pm
content: Just became an owner of Korad KA3010D lab PSU. For a few decades I was using pure analog coarse/fine linear lab power supplies and got tired of ringing/bouncing wipers of potentiometers leading to unstable voltage/current control.Well, this Korad PSUs have OVP and OCP features.An idea behind OCP is absolutely clear: when actual current reaches (for whatever reason) a set point, instead of just limiting the current by lowering output voltage the device will completely switch its output off. Indeed, in some cases if you know your load will not draw more current under constant voltage than some known value, if it eventually start to draw, it DEFINITELY means something went wrong in your circuitrarty and immediate shutdown will indeed PROTECT something in your load.OVP is different story. I can't get an idea behind this feature. If your load is always sinking current/energy, then UNDER NO CIRCUMSTANCES voltage on the output terminal may become higher than what you set on you Korad PSU. And thus OVP is just useless since in never happens to have OV condition. But if your load can sometimes become a source of electromotive force itself and start producing power, then, yes, voltage on output terminals may become higher than what you just set. An example of this may be a DC motor which, if spinned by some external force, may become a voltage generator rather than consumer.Okay. But! Turning off series pass transistor of the PSU in such condition does not make any difference. If you set your PSU to output 15V and your load started to produce 20V on it's terminals, switching off PSU will not cancel this 20V to be present on output/input terminals.So what does this overvoltage protection really protect? What it intended to protect? If it is intended to protect the load from overvoltage condition, then it is useless since the load itself generate this overvoltage condition and it will keep producing it despite of PSU series-pass transistor state. If it is intended to protect the PSU itself (rather than "load"), then, again, it doesn help at all since voltage produced by load will be still present on internal circuitrary of the PSU (unless there is a relay which physically disconnects PSU's output terminals from PSU internal circuitrary).On the other hand, if an idea behind OCP is "instead of current-limiting just immediately prevent any current from flowing out of PSU", OVP must (by analogy) work as follows "instead of voltage-regulating just immediately prevent any voltage to be present on PSU terminals". To achieve this PSU must short its terminals when OVP is triggered. However, even if such such OVP is not turned on, "voltage-regulating" ability of the PSU has to include sinking current from extenal device to keep voltage on predefined level, not just sourcing current.At this point we come to something what is called four-quadrant power supply.An ideal voltage source is four-quadrant: it can produce positive voltage and source current, positive voltage and sink current, negative voltage and sink current and negative voltage and source current. I believe (even though I didn't look though schematic or revese-engineer it) Korad PSU is not even a two-quadrant PSU — as it is true for almost every lab bench PSU of this class and price. It can only produce positive voltage and it can only SOURCE current (but not sink).So, if it has single-quadrant operation by design, then having OVP which shorts PSU's terminal is inconsequent. If only it was, it would be reasonable if without OVP the PSU tries to keep voltage at defined value even by sinking current from the "load" (in quote-marks, because the "load" itself produce a voltage) literally pulling down "V+" rail to "V-" and with OVP switched instead of clamping voltage by sinking current it shorts its terminal to completely remove any voltage from the terminals (like in case with OCP it completely "removes" a current from the output).So, I am almost sure Korad is single-quadrant operation. And if so, it is likely not going to short its terminals on OV-condition. And just switching off series-pass transistor does protect neither the PSU nor a "load" from overvoltage.So, what's the point and how it is intended to work?

author: ataradov
author_rank: Super Contributor
timestamp: January 14, 2025, 12:43:25 am
content: I think the idea is to just disconnect the power supply when something unexpected happened to not make things worse potentially. It may not be a constant thing, but if something in the powered circuit periodically starts to be a source, then it makes sense to turn the power off as soon as possible and not subject the circuit to over-voltage condition longer than necessary.

author: thm_w
author_rank: Super Contributor
timestamp: January 14, 2025, 01:11:19 am
content: If I'm working with a sensitive 3V device, I can set OVP to 3.5V and prevent accidentally sending excess voltage to the device.Yeah?https://www.reddit.com/r/AskElectronics/comments/48ujfe/please_help_me_understand_the_over_voltage/https://www.us.lambda.tdk.com/resources/blogs/20231025.html

author: ataradov
author_rank: Super Contributor
timestamp: January 14, 2025, 01:50:29 am
content: I guess it also helps against wrong user input too. If you get too happy with a knob, it will prevent damage. Although more useful version of the feature would be a user limit where PSU itself does not generate more than some set limit. And may be turn off the output if it sees that it can't regulate the output.

author: firehacker
author_rank: Contributor
timestamp: January 14, 2025, 09:27:37 am
content: Quote from: thm_w on January 14, 2025, 01:11:19 amNo, you can't. There is no two different voltage settings in Korad PSU: normal output voltage and overvoltage threshold. There's only one voltage setting: output voltage. That's it.And if you are working with sensitive 3V device, you are going to set 3.00V as output voltage. And even without OVP functionality any decent PSU will not go higher than what you set, so the PSU itself can't cause overvoltage. The device-under-power actually can cause overvoltage if it contains switchable caps or inductors or other source of EMF such are thermo- or photovoltonic cells, motors and so on. But in this case the device overvoltages itself, not the PSU. I mean PSU can't protect device from creating overvoltage on device's power rails.QuoteYou are confusing LOCK button functionality with OVP functionality. If you mean unintentional rotation of the know leading to overvoltage.If you mean the other thing: trimming upper boundary of the range in which user can change voltage by rotating know, this is not the case for KAxxxx PSUs since there are no such thing as adjustable upper boundary of accessible voltages range.For KA3010D full available voltages range is 0V to 31V. If you mean that one want to limit himself say for being able to adjust voltage (by turning a knob) only in range from 0V to 5V — no, that isn't how OVP works on Korad. You can't set OVP to 5V and then go anywhere from 0V to 5V by careless rotating knob being sure that PSU won't let you above 5V.a) You can't set OVP threshold to arbitrary voltage, there's no such settings. There's only one voltage setting: the output voltageb) There is no setting that limits the range of voltage adjustment.

author: tom66
author_rank: Super Contributor
timestamp: January 14, 2025, 12:58:04 pm
content: A good example of use might be if testing a sensitive semiconductor. You might want 0.05A to flow, which drops 3V, e.g. a laser diode. If you are probing the circuit maybe you open the connection briefly and voltage goes up to e.g. 5V. This might be bad, so you want the supply to turn off, not limit the voltage. Perhaps as temperature changes, the forward voltage might increase, so the protection provides an upper limit without having to tweak the operating voltage.Remember often PSUs like these are used in production control by non-skilled operators. That means you don't necessarily want to explain something like this to them, you want a supply that won't kill your devices.

author: firehacker
author_rank: Contributor
timestamp: January 14, 2025, 03:03:15 pm
content: Quote from: tom66 on January 14, 2025, 12:58:04 pmGood example. Assume we set U=5V and I=0.05A. Laser diode is connected, current is limited to 0.05A and PSU is in CC-mode. Real voltage drop is 3V — less than what we set (5V).If diode connection becomes loose, indeed voltage on PSU terminals will start to increase up to 5V.But!1. No matter whether OVP is turned on, output voltage will go up to 5V in both cases (engaged and disengaged OVP). Even if OVP is enabled, immediate shutdownwill not occursince it requires voltage to be a bit greater than 5V, but it will stop growing at exactly 5V (unless we have totally crappy PSU which tends to overshoot).So OVP will never be triggered in your scenario with laser diode.2. There is a big electrolytic capacitor across PSU output terminals. The current sensor (shunt) is located before this cap and thus the process of charging this cap is subject to overall current-limiting. And if you set current to 0.001A and voltage to 31V and enable PSU output, it takes around 10 seconds to gain full output voltage (because cap is charged by constant current and its voltage is described byI=C·du/dtlaw). So will not "blast" to full value immediately: it's relatively slow process and slew rate it limited by CC mode and amperage setting, and is not affected by OVP in any way.And returning to you example: setting U to 3.000V will prevent output voltage to goint up to 5V when opening the circuit. So OVP is not necessary in this scenario (just set proper output voltage) and wont be triggered at all.

author: tom66
author_rank: Super Contributor
timestamp: January 14, 2025, 03:13:14 pm
content: Right, but you're missing what I'm saying - it's a protection that applies in non-normal conditions, not a normal operating limit.So the PSU has a cap on the output. That cap if charged up to 5V @ say 470uF could easily nuke that laser diode since theoretical current will be several amps if it is reconnected while live. I have done this before in the lab when I was a junior engineer. It is embarrassing explaining to the senior engineer there that you just destroyed that £300 laser diode because you were careless.Now you don't want to set the PSU voltage to 3.000V because as the diode warms up its forward voltage increases to say 3.5V.And you don't want to have to constantly tweak the diode forward voltage because you are trying to characterise it under constant current, like measuring forward voltage at 50mA.Setting OVP to 5V means that as soon as the load opens on the PSU, the voltage will climb above 5V and PSU will shut off - this is a fault protection rather than a dynamic limit. Now, your unskilled operator (err... or junior engineer) doesn't blow up the diode when they fiddle with the PSU leads. The PSU has turned off ... in most cases locked out ... so the instinct to just turn back on won't work, you get a moment to 'think' and fix the problem.

author: firehacker
author_rank: Contributor
timestamp: January 14, 2025, 03:45:26 pm
content: Quote from: tom66 on January 14, 2025, 03:13:14 pmWhich conditions exactly? Could you please bring an example of such conditions?And the main question: is it to protect DUT from PSU, or to protect PSU from DUT? It is important, but, finally, neither of these takes place in case of just turning off series-pass transistor.Quote from: tom66 on January 14, 2025, 03:13:14 pmTrue. And I expect you understand that neither OVP nor OCP helps here. No way diode can be saved by PSU since there is nothing between big CAP charged to 5V and non-linear (in terms of Ohm's law) load such as laser diode. So this example with laser diode is legit but is has nothing to do with OVP mechanism at all.Quote from: tom66 on January 14, 2025, 03:13:14 pmSet it initially to 3.5V or whatever voltage you consider absolute maximum for your particular diode. It is really enough to just set maximum allowable voltage for you diode as the output voltage of Korad PSU to not let it become above that value. OVP is not needed and, anyway, it will not be triggered in your scenario. Shutdown will not occur!QuoteYet again: there is no such things as "setting OVP to 5V" as soon as there is no separate "OVP threshold voltage" parameter. OVP cannot be set to 5V or whatever in this PSU. It may be turned on or turned off.QuoteNo wayoutput voltage will ever climb above 5V if you suddenly disrupt the circuit. CV-mode has always a priority over CC-mode. This PSU cannot work as constant-current-source with uncontrollable voltage growth in no-load condition.You probably talk about some hypotetical PSU, but I ask about Korad KA3005. KA3010 and so on.

author: tom66
author_rank: Super Contributor
timestamp: January 14, 2025, 04:01:55 pm
content: I already gave a detailed explanation. Sorry, if that's not good enough, I'm not writing it again.If you set the PSU to 3.5V output, when the diode is cold, if the PSU is in OC condition, it could still burn the diode. Therefore, you want to be really, really sure that the load is present before the PSU turns on.Now you probably would not use cheap Korad PSU for something like that, but this explains why the function exists, OVP is to shut the output off, voltage limit is a different parameter. I do not have a Korad PSU to test right now, so can't see what the function actually is like. If it is like you have described, maybe it is not that useful.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 14, 2025, 04:06:01 pm
content: I agree it won't make much sense.Maybe they copied theideaof OVP from some other (2-quadrant) power supplies so that they can say they "have OVP". But it is possible it protects the DUTin case of some type of power supply failure. Of course, fixing the power supply not to fail that way, or forcing this OVP always-on would be then better idea.E.g. in some HP/Agilent power supplies there is an actual crowbar circuit which activates at configurable OVP (for example, by default at 22V with maximum CV setpoint is 20V), capable of sinking a lot of current - of course fused, I managed to blow this fuse by connecting a battery to output and accidentally triggering the OVP.These Korad things are cheap-ass supplies, I don't think there is any great design behind them and as you say I can't understand the OVP function either and apparently nobody else can do (they are just making up some illogical excuses in an attempt to explain it to no avail).

author: Siwastaja
author_rank: Super Contributor
timestamp: January 14, 2025, 04:08:01 pm
content: Quote from: tom66 on January 14, 2025, 04:01:55 pmI didn't understand it either. The only way it makes sense is that the internal OVP mechanism had better reaction time than the CV mode. Which is a remote possibility of course, but it would be nice to see it documented somewhere.Output capacitance is a big issue when lab power supplies are used on sensitive constant current loads (like laser diodes), but I don't see how that is relevant with the OVP question at all. A super-fast OCP (with very little output capacitance behind it) would be relevant.

author: tom66
author_rank: Super Contributor
timestamp: January 14, 2025, 04:12:46 pm
content: It makes sense when you want the function of the power supply to turn off the output when the load is open circuit and the output voltage of the PSU would deliberately go over the OVP limit because that is the behaviour you intend. In that case you might set the PSU voltage to 5.5V, OVP to 5V, that means with no load, PSU voltage will hit OVP, PSU will shut down. Any load that brings PSU voltage below OVP threshold will keep PSU on.I do not know whether the Korad PSUs do this though, I thought the question was more general than that.

author: firehacker
author_rank: Contributor
timestamp: January 14, 2025, 05:40:42 pm
content: Quote from: tom66 on January 14, 2025, 04:12:46 pmKoradDOES NOT HAVEtwo separate settings for voltage. That's the point. I repeated this many times.Only output voltage and output current. Neither of these can be delibetery exceeded by the PSU, this PSU like many other linear lab PSUs will never produce a voltage greater then what you set to force the current up to your setting. I.e. the PSU itself never overvoltages in flavour of keeping constant-current mode. CC mode is active only when load tries to draw more than you allow to feed. Otherwise CV-mode is doing its business.The only way overvoltage condition can occur with this Korad (in my point of view) is only if a device connected to the PSU (a "load") is producing its own voltage and the current flowsintopositive PSU terminal from the "load" (rather from PSU to load as in normal case) charging Korad's output capacitor above Korad's set point. Yeah, in this and only in this case Korad will detect overvoltage, but switching everything off inside Korad won't prevent external device (feeding current to Korad instead of drawing current from Korad) from resuming charing of Korad's internal output cap.This means neither Korads output capacitor is protected from overvoltage (it will be overcharged by the "load" behaving as power source), nor the strange "load" (or at least parts of it that are sensible to overvoltage) is.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 14, 2025, 05:46:52 pm
content: Quote from: firehacker on January 14, 2025, 05:40:42 pmOne thing that comes in mind: maybe it is useful to detect short externally generated voltage spike and react to it by alarming user that overvoltage was present, and refusing to continue operation after the external spike is gone. LC ringing from hotplugging a large low-ESR capacitor bank would be a typical example where the DUT sees overvoltage - and probably the supply also sees it. But this is probably far-fetched and not the correct explanation.

author: mawyatt
author_rank: Super Contributor
timestamp: January 14, 2025, 05:51:48 pm
content: Our Korad KWR102 and 103 behave as described, basically the OVP and OCP seem to do nothing wrt to the supply outputs.See later post!!The Instek GPP4323 behaves as we expect when the OVP or OCP limit is reached the supply quickly turn the output OFF.Same for Korad KWR102 and 103, see post below.The Instek behavior is what we expect from a Lab Bench Type Supply wrt the Over Limits and why we don't consider the Korad for that type use. It's a high current & power source (SMPS type) not intended for sensitive electronics use, where we used these for driving motors/solenoids/heaters and other high current loads.SMUs are intended for 4-Quadrant use, and their price reflects such!!Best

author: tom66
author_rank: Super Contributor
timestamp: January 14, 2025, 05:53:27 pm
content: In which case, yes, I agree, it doesn't seem to be much use to have the OVP as implemented. I do not have a Korad PSU to evaluate the behaviour and wasn't aware of that limitation. Perhaps it's a case of someone in sales/marketing saying "we need OVP" but the engineers not really understanding why.

author: mawyatt
author_rank: Super Contributor
timestamp: January 14, 2025, 06:03:33 pm
content: Quote from: firehacker on January 14, 2025, 05:40:42 pmThis is not exactly true with respect to our Korads KWR102 and 103, you can set the OVP and OCP independent of the VSET and ISET,but they apparently do nothing.So they have the Separate Settings but the OVP and OCParen't engaged, which brings up an interesting point; Did/Does Korad intend for these to become active or are they just Ornaments for Perceived ValueUpdate: Classic case of RTFM in detail!! On the KWR102 for the OCP and OVP function to be enabled you need to short press the function key after entering the value then the ON/OFF key which different than the way the CC and CV Limits are set where you press the rotary knob to enter the value. The short key press followed by short ON/OFF key press toggles the OCP or OVP function On and Off. You must also use the respective VSET and ISET buttons to change the decimal range for the rotary knob, but they are separate settings between VSET and OVP also ISET and OCP.We've never used this function, but it seems to work altho the sequence and means to activate these functions seems somewhat awkward.With due respect for the Korads we have (after somewhat bashing them) they have good accuracy and noise considering they are a high current/power SMPS, another nice feature is the 4 wire Kelvin Sense built-in, altho wish these were available on the front.Anyway, thanks to this thread we've discovered a feature within our Korads that is new to us and potentially useful in the futureBest

author: thm_w
author_rank: Super Contributor
timestamp: January 15, 2025, 01:54:00 am
content: Quote from: firehacker on January 14, 2025, 09:27:37 amMakes no sense, OVP/OCP are always independently configurable.

author: mawyatt
author_rank: Super Contributor
timestamp: January 15, 2025, 02:05:38 am
content: Quote from: thm_w on January 15, 2025, 01:54:00 amAgree, even if it's a little awkward with our Korads, and they both work as they should IMO....disabling the output when exceeded (either Current or Voltage)."firehacker" needs to remove that statement and the other related to such in our post above, or at least change statement as not all Korads behave this way, ours don't!!Best

author: firehacker
author_rank: Contributor
timestamp: January 15, 2025, 10:33:20 am
content: QuoteI thought it's obvious that (since my topic starts with "Just bought Korad KA3010D") here in this topic "Korad" means this particular device or this particular family (Korad KA3005, KA3010, KA6005, etc).Quote from: thm_w on January 15, 2025, 01:54:00 amMakes for OCP.The current setting is already a sort of limit.Load tries to take more current than you set and OCP=off ———> Current limiting occurs.Load tries to take more current than you set and OCP=on ———> Immediate shutdown occurs.The same analogy cannot be spreaded onto voltage, because while current is defined by the character of load (and PSU can react on it), voltage is defined by the PSU itself (and there's not much sense reacting on wrong voltage if the voltage is completely depdentent on PSU's "will").

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2025, 11:01:04 am
content: Quote from: firehacker on January 15, 2025, 10:33:20 amOf course the same thinking can be applied to OVP:Load goes low-resistance enough and OVP=off --> voltage limiting occurs (CV mode)Load goes low-resistance enough and OVP=on --> immediate shutdown occurs.Then the supply would act like a current source does, and load needs to be connected before enabling the output (or, output shorted externally) to prevent unwanted OVP triggering.I don't know if it works that way or is even supposed to work that way, but just saying that a lab supply is in control ofbothcurrent and voltage, and there are at least three sensible operating modes:CC - CVCV - OCPCC - OVPedit: typo fix

author: firehacker
author_rank: Contributor
timestamp: January 15, 2025, 01:43:54 pm
content: Quote from: Siwastaja on January 15, 2025, 11:01:04 amWhat OCV stands for?Same thinking could be applied if this PSU were capable of working in CC-mode primarely. I.e. "it going to produce any voltage in order to keep current at specified level". But no, it becomes CC only on overcurrent and lowers output voltage in order to reduce the current down to the required level.So PSU control logic can make output voltage either exactly as you wished (if no overcurrent happens), or make it lower (in order to fight overcurrent), but it never makes voltage higher than you configured. And thus overvoltage can never occur (caused by PSU control logic). No matter how you configure this particular Korad, no matter what the load is trying to do, overvoltage can never happen. One exception is the the case when a "load" can somehow produce it's own voltage that is greater than PSU's output voltage (reversing current/power flow direction from normal "PSU to LOAD" to "LOAD to PSU").

author: 2N3055
author_rank: Super Contributor
timestamp: January 15, 2025, 02:26:57 pm
content: Quote from: firehacker on January 15, 2025, 01:43:54 pmEvery (real life) CC source will have something called compliance voltage, i.e.max voltage it can apply to output while servoing to achieve set current.So on GP PSU voltage setting is actually compliance voltage, and current limit is actually required constant current.If load is such that it cannot satisfy CC requirement with set compliance voltage, it will then work in CV mode.Overvoltage protection is probably a remnant of what used to be crowbar overvoltage protection. And yes it is there to ensure something else raises the voltage.Some PSU actually still have real crowbar protection, and occasional user finds that out when trying to charge large batteries.OVP can be used for thing where you need termination when certain voltage is reached.Laboratory PSU are just that. They have some functions that might not seem obvious but when experimenting might come in handy for some idea.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 15, 2025, 02:49:17 pm
content: Quote from: firehacker on January 15, 2025, 01:43:54 pmTypo for OVP (overvoltage protection), fixed in the post now. OCV would be open-circuit voltage (e.g. of a battery), somehow my brain was consistently producing the same wrong three-letter acronym.

author: mendip_discovery
author_rank: Super Contributor
timestamp: January 16, 2025, 07:05:43 pm
content: I have always taken it as a safety measure for when you don't want to accidentally set the voltage too high when you are having amoment and want to avoid having amoment after sending too much voltage into a very expensive bit of kit.OVP = Over Voltage ProtectionOCP = Over Current ProtectionHow often are you, not quite paying attention and going to turn the power up by 1 V and accidentally put it up by 10 V as it was highlighting the wrong digit, or adjust the voltage when you thought you were adjusting the current. Remember there are many members in EE that have yet to realise they are actually meant for R&D (wReck-it & Destroy)

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2025, 08:15:33 pm
content: Are people really not reading?You can't treat it as a safety feature, since there is no separate setting for the "safe" threshold. You just set the voltage you want and it turns off the output if it senses that the actual output is higher. This can only happen if the target sources the current into the supply. Which seems marginal ans useless.

author: thm_w
author_rank: Super Contributor
timestamp: January 16, 2025, 10:25:37 pm
content: Quote from: ataradov on January 16, 2025, 08:15:33 pmThe manual seems to be confused too:Quotehttps://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/4151/KA3000_6000_Series_Man.pdfCan you set the voltage, turn on OVP, and then reduce the voltage? Maybe that is how you adjust it.

author: tom66
author_rank: Super Contributor
timestamp: January 16, 2025, 10:34:27 pm
content: Yes but as firehacker has made clear that doesn't really make sense as a feature. I guess it could beep at you if the voltage goes over the limit, but it can't do anything to stop that.I can only see this function as needed as I described it, to protect certain devices from overvoltage when an open circuit occurs, but even then it is a very niche case.

author: ataradov
author_rank: Super Contributor
timestamp: January 16, 2025, 10:54:28 pm
content: I poked around at KA3005 and I see no way to set the voltage. Anything you can adjust leads to the output voltage change.And I tried to connect 9V battery to the output and it does disable the output in that case.I think they are just reusing the firmware or documentation and did not correct it for this device.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 17, 2025, 08:51:59 am
content: Quote from: ataradov on January 16, 2025, 10:54:28 pmYeah. This is what you get with this cheap crap. To be fair, these Korad supplies (and many of their copies) are still much much better than the previous generation of cheap crap lab supplies which literally blew up as short circuits if you applied the 9V battery to the output. Or were not able to current limit at all below 1.2V. Or just blew up randomly for no reason whatsoever.But it is not surprising they have implemented extra feature which they don't understand themselves and neither do the users. Oh well, at least it doesn't blow up when enabled.

author: tom66
author_rank: Super Contributor
timestamp: January 17, 2025, 11:33:58 am
content: The early Korad supplies definitely had a really bad problem with shorting their pass transistors. That is one case a non-adjustable OVP function may benefit, since the supply has a relay on the output, at least you could refuse to turn the output on after such a fault occurred. It should just be a default function if the output voltage climbs over the normal voltage set point by more than 1-2V. But no...they work fine, just with raw transformer voltage on the output, range dependent.

author: ataradov
author_rank: Super Contributor
timestamp: January 17, 2025, 02:25:41 pm
content: Quote from: Siwastaja on January 17, 2025, 08:51:59 amIt is a fine supply and over the years of using it I have not given that feature a second thought. My guess is that they just had rubber buttons made and did not want to change things for the new supply, so they implemented the feature the best they could. And it does something. There may be limited applications where it is useful, but it is not broken and works for what it is. I'm sure someone will find it helpful.