Looking for a replacement current display for my variable power supply. - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: December 03, 2013, 12:52:40 pm
content: Alright so for some reason, my variable power supply started having issues, I first noticed this:Then I noticed that on small loads, like a fan for some reason it thinks I'm drawing 20 amps sometimes. I opened it up and all the boards looked fine so I figure somehow the micro controller on the display board got ruined, and am looking for a replacement. It looks like a fairly generic cheap one you could find on ebay from china, I haven't found any similar ones though and the number doesn't bring up anything so I was hoping some of you have seen one recently/will have better luck finding a replacement than I did. I'd much rather spend probably $4-@$10 on that part or a similar one that would fit, rather than buying a new 30v 5 amp power supply. The voltage still shows fine it just bugs me is all.That fourth character or so is a 7, not a z.

author: XOIIO
author_rank: Super Contributor
timestamp: December 03, 2013, 01:04:07 pm
content: Also on the topic of power supplies at one point I'll want a dual channel one but I came across this. What do you guys think? I figure it would actually be decent for the stuff I do that doesn't require absolutely precise voltages and a bit of overshoot doesn't matter, a triple channel one would be pretty sweet although it would take up a lot of room on my desk when I use it.http://www.ebay.ca/itm/360744987934?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649edit: ah, that other channel is fixed 5v. Still, not bad it seems although I could grab a simpler dual channel one for less.

author: dr.diesel
author_rank: Super Contributor
timestamp: December 03, 2013, 01:08:24 pm
content: Quote from: XOIIO on December 03, 2013, 01:04:07 pmI have the Mastech version of the above, got it second hand really cheap, been using it for several years when I need > 3 amps. Does a fine job when you only require basic CV/CC.

author: dr.diesel
author_rank: Super Contributor
timestamp: December 03, 2013, 01:17:19 pm
content: Just noticed, the power supply you found on eBay is not a direct clone of the Mastech that I have. Mine has the power transistor heat sinks mounted on the back, which would likely provide much better cooling, without actually seeing the design of the model you found.You can see a glimpse of this here:http://www.ebay.ca/itm/MASTECH-HY3003D-3-30V-3A-Triple-Linear-Output-DC-Power-Supply-Variable-Regulated-/330887496024?pt=LH_DefaultDomain_0&hash=item4d0a6e8158&_uhb=1Note that one is not a direct clone either as the display on mine is LED, and capable of > 5 amps.

author: XOIIO
author_rank: Super Contributor
timestamp: December 03, 2013, 01:20:38 pm
content: Quote from: dr.diesel on December 03, 2013, 01:17:19 pmah, yeah this one I have also has the black heatsink on the back.The next one I get I want to be LED so I can see it in the dark and maybe swap the 7 segment displays out for a nice blue or green.

author: Skimask
author_rank: Super Contributor
timestamp: December 03, 2013, 01:33:25 pm
content: Like a couple of these?(They're not blue or green, but they are red LED)

author: XOIIO
author_rank: Super Contributor
timestamp: December 03, 2013, 01:41:59 pm
content: Quote from: Skimask on December 03, 2013, 01:33:25 pmSimilar but these ones are LCD, and a bit larger profile I believe (I'd need to grab my calipers and check later.)

author: rsjsouza
author_rank: Super Contributor
timestamp: December 03, 2013, 03:17:22 pm
content: Depending on where you live, you may want to checkthis LCD displayat BG Micro (they have a datasheet for download). They seem to be out of stock, but I suggest you to contact them and see if they have some more arriving.

author: Bored@Work
author_rank: Super Contributor
timestamp: December 03, 2013, 07:07:19 pm
content: Quote from: XOIIO on December 03, 2013, 12:52:40 pmDude, even people with AHDS won't be able to figure out what you are complaining about from that crap video.QuoteThe ICL7106 is not a microcontroller. It is a 3 1/2 ADC with LCD driver. 40 years old stuff. Still manufactured by two official manufacturers (Intersil and Maxim) and a bunch of chines cloners. Available in almost all friendly (and not so friendly, Farnell ...) online shops for maybe $6. And for half of it on eBay.Replace the IC if you really think it is broken. But I have my doubts. Anyhow, since the surrounding circuit is so well documented and the IC is in a socket there is really no excuse for not checking all parts on the PCB.

author: XOIIO
author_rank: Super Contributor
timestamp: December 03, 2013, 07:11:08 pm
content: Quote from: Bored@Work on December 03, 2013, 07:07:19 pmwell, I figure it has to be something on that board considering it has V+/- and in+/-, it must be the thing sensing the current right?

author: Andy Watson
author_rank: Super Contributor
timestamp: December 03, 2013, 07:37:35 pm
content: Download the data sheet for the intersil version of the 7106. It has an application note(s) that will almost certainly correspond, one-for-one with the circuit on that display board.Quote from: Bored@Work on December 03, 2013, 07:07:19 pmYeah, +1, you might consider putting a tripod on your shopping list

author: XOIIO
author_rank: Super Contributor
timestamp: December 03, 2013, 07:42:24 pm
content: Quote from: Andy Watson on December 03, 2013, 07:37:35 pmI have one but it's leg is broken, and considering it was only a minute and a half video it wasn't worth setting up with tape on the led/phone and having it in the way.Quote from: Bored@Work on December 03, 2013, 07:07:19 pmGuess what, maybe try thinking that not everyone can afford a several hundred dollar camera and have to make do with what they have before acting like a prick

author: envisionelec
author_rank: Frequent Contributor
timestamp: December 03, 2013, 11:35:21 pm
content: Quote from: XOIIO on December 03, 2013, 07:42:24 pmWoah...I'm counting two computers on your desk. I think you can afford a tripod and a better attitude.These Mastech clones are pretty cheap. I think you're looking at a failed solder connection in the current measurement circuit and not the display. The 1xxx reading is "over range".

author: mariush
author_rank: Super Contributor
timestamp: December 03, 2013, 11:49:08 pm
content: Dude... if you don't have a tripod, you could simply get a chair and a bunch of BOOKS to get the height level you want.Some people actually get sick from too much motion and it makes your videos horrible... too much jerkiness to be able to follow.Now moving on to your issue. ICL7106 is a multimeter chip with a lcd display driver integrated in it. The lcd display that's on that board is a custom made LCD which has the pinout layed out exactly as the ICL7106 chip has the pins for the anodes and cathodes (the segments on the display).The display is probably fine. If the ICL7106 is broken, replacing it will also get the the lcd display working.ICL7107 is the same thing as ICL7106 but instead of driving lcd segments, it works with LED segments and has integrated all that stuff about driving seven segment displays in them.If I remember correctly, the meter needs a split power supply to work, so your board should have -5v, +5v and ground but it could also be -5v and +8v ... I think the maximum allowed is 15v between the supplies.So check the input voltages to that board, then check what comes into the board signal wise with a multimeter.Simplest way to see if the IC is dead ... take it out and put the chip from the other board in it and see if that works, then put the presumed dead chip in the board known to work ... worst case scenario you have two dead ICL7106.Then check the current shunt, check the opamp on the pcb, make sure there's a voltage going to the opamp and that it's not faulty and you get some signal out of that opamp etc etc etc

author: smashedProton
author_rank: Frequent Contributor
timestamp: December 04, 2013, 12:20:58 am
content: Quote from: envisionelec on December 03, 2013, 11:35:21 pmThey look like gaming computers too

author: XOIIO
author_rank: Super Contributor
timestamp: December 04, 2013, 02:44:56 am
content: Quote from: smashedProton on December 04, 2013, 12:20:58 amOne of them was at one point, and they are both second hand outdated crap that can't play modern games worth much at all. All of the computer stuff I have is second hand stuff that I had to fix, same thing with my monitors, I got them because of either faulty power supplies or damage on the screen and nobody else would buy them, not to mention I had to put in many hours of volunteer work to get the price down. And I'll act with a better attitude when people don't bitch about stuff, I don't need that shit on top of everything else.Back on topic, the display sometimes even reads 15 amps with no load and a couple volts set. When I took it apart all the solder connections for the wires were in good shape. I wish I remembered how it even started doing this, it was just random though I think.

author: envisionelec
author_rank: Frequent Contributor
timestamp: December 04, 2013, 02:55:51 am
content: Quote from: XOIIO on December 04, 2013, 02:44:56 amNobody knows what you're dealing with so don't make it part of the conversation if you want to get legitimate help.It shouldn't read anything more 0.00 if no load is connected. I think you're dealing with a high impedance ground on the main board or an opamp with one missing rail. More troubleshooting is required.

author: mariush
author_rank: Super Contributor
timestamp: December 04, 2013, 03:56:35 am
content: Yeah, he should take it step by step ...First rule of diagnosing ... though shall check voltages.. check all the voltage rails +5v , 12v , 8v, -5v,-8v if any ... check the linear regulators if any.... There was something iffy in the video with the relays triggering in a weird way... could be the opamp triggering the relays was not powered properly.So then check the opamps, then see if you have some shorted diodesBut somehow I feel he's too careless and can't pay attention for enough time to do a honest attempt to fix it... just based on the few videos i skimmed through and the camera shaking.

author: XOIIO
author_rank: Super Contributor
timestamp: December 04, 2013, 04:02:49 am
content: Quote from: mariush on December 04, 2013, 03:56:35 amAnd here I figured this community might have a few less douchebags compared to standard forums, looks like I was wrong.

author: mariush
author_rank: Super Contributor
timestamp: December 04, 2013, 05:07:48 am
content: Well what do you expect?Read your posts in this thread from the top ... from the start of the thread it's kinda obvious you barely know what you're doing.From the video, I can tell you have no clue because you're just talking crap and twisting the knobs and you fail to even hear the relays making contact, which means something connects various taps of the linear transformer together. But since you don't see any change on the displays ... it should tell you something. Either the relays trigger erratically (and then you'd follow the circuit to see what could trigger the relays which could tell you that something is faulty) or check other stuff in the power supply.Then from your post ... you're just "jumping the gun" and assuming those indicators are faulty when in fact you don't know that. Then you think those are microcontrollers, which tells me you didn't even bother to search google for "ICL7106" to find out it's a 3 1/2 multimeter IC which would then further tell you that lcd display is a custom one and so on.Then I don't see any mention of you actually mentioning the voltages in case one of the low voltages used by the circuit is missing... and i don't see a snapshot of the actual circuit board, just in case someone here on this forum may want to point you to check a particular IC, or tell you to see if a voltage reference is bad or not, or to see if a particular zener diode or plain diode is broken/shorted ...Yeah, it's just much easier to make shaky videos and play (in a stupid way) with high voltage without any safety and make other people you don't know anything about douchebags.

author: XOIIO
author_rank: Super Contributor
timestamp: December 04, 2013, 05:23:29 am
content: Quote from: mariush on December 04, 2013, 05:07:48 amActually, the relays are pretty fucking obvious and those are switching in the taps for the voltage, and they were behaving the exact same way they did when the amperage display worked properly, also, I did not care about the voltage readout as that was working fine, and maybe try looking at the date the video was posted, I have checked further into this problem since then, checking voltages and diodes.News flash, not everyone is at the same electronics knowledge as you, I have not worked with op amps, so maybe consider that people's experience may vary before being a prick. Considering these power supplies are made in china, I figured the controllers on the back of the LCD segment also handled reading the current/voltage in a similar way that other cheap amperage and voltage displays from ebay do, that is why I figured that is where the problem lies considering the connections were all in good shape and my multimeter showed a proper amperage reading when hooked up with a load.Guess what, this thread was not about the production quality of the video, it was about an issue I found. You don't think I know it isn't great quality? Big fucking whoop you can see the results of whatever problem there is. If you have a problem with it don't watch it.Apparently here there are stuck up pricks as well who think that just because someone knows less than them they know nothing at all, instead of taking the time to consider that different people may be at different levels.And if you think I'm behaving badly bit whoop, I'm sick of the shit people hand out all the time, assuming shit and feeling all high and mighty about it and I'm tired of taking that shit from people so I'm going to speak my mind when someone acts like that.