Author Topic: My first new Lab Power Supply started to burn after 5 minutes  (Read 2063 times)

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LambdaMikel

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This is great... yesterday the "SID CHIP OF DEATH" and today my first new Lab PSU arrived:


https://www.amazon.com/gp/product/B07512KQDW/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1#customerReviews
Well, what can I say. At first it wouldn't even light up a simple LED. I figure - well, maybe the LED does not take enough current or something. So, I followed a YouTube video tutorial


https://www.youtube.com/watch?v=T8Z2EFrbtpU

And I did the + / - "short circuit" and tested up to 1 A. All fine. 

OK, I thought, now for the next round and a real test. I used an old VFD Pacman Handheld Game, usually powered by 4 x 1.5 V batteries, I connected it to the terminals. Set the voltage to 6 V. Amps show 0. Good. Of course, polarity of the terminals was correct. Turned on the game and the whole PSU starts to BUZZ and SIZZLE and SMOKE!!! Of course I turned of the game immediately. The PSU continued to sizzle and smoke and the LED displays start to blink and flicker. Pulled the plug as soon as possible. Now, packaging it up again for Amazon return, I can tell that a part inside has come loose. The fuse didn't even engage. Smoke is filling my room. WHAT A PIECE OF C***!! I can't believe that has passed quality control. BEWARE!!!
Putting back the batteries in the Pacman game - well, it still works!!!
« Last Edit: 09:40, 25 October 19 by LambdaMikel »

Offline Bryce

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Oh, you should have asked first. These things are known to be a heap of shite. There are decent supplies out there for a bit more money. This isn't one of them.

People also tend to underestimate the importance of a good bench supply. The cheap ones can have over-shoot and noise that can destroy your circuit. It's well worth spending a bit more on a supply.

Bryce.

LambdaMikel

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Right, well this one fit the bill and given all the 5 star reviews I thought - give it a try.
I AM SO HAPPY that I did not connect it to a CPC or something like that...


@Bryce can you suggest a (much  ;D ) better one in a slightly higher price range?
« Last Edit: 10:12, 25 October 19 by LambdaMikel »

Offline Bryce

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I should also mention that that supply is a switched mode device. I don't recommend these as bench supplies, you should really be looking for a linear supply.
I'll do a quick search and make some recommendations.

Bryce.
 

Offline Bryce

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Starting from the top of the price range (well top in this case, you can spend thousands on a serious supply!):

Two channels, linear, very reputable maker:

https://www.amazon.com/Siglent-Technologies-SPD1168X-Programmable-Reading/dp/B07FD1NX97

Cheaper but only one channel:

https://www.amazon.com/KORAD-KA3005P-Programmable-Precision-Adjustable/dp/B0085QLNFM/ref=sr_1_5?keywords=Korad+bench+power+supply&qid=1571988259&sr=8-5
Even cheaper, but not programmable:

https://www.amazon.com/KORAD-KD3005D-Precision-Adjustable-Regulated/dp/B00FPU6G4E/ref=sr_1_3?keywords=Korad+bench+power+supply&qid=1571988340&sr=8-3

Bryce.
(No idea why the forum messes up the format. Those big spaces are neither in the edit box nor the preview screen).
« Last Edit: 10:28, 25 October 19 by Bryce »

LambdaMikel

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Thanks @Bryce
This is great - maybe the smallest one is good enough for me. I don't think I need a programmable one - unless you can convince me otherwise of course  :)
 Btw, I found the +/- connection odd... I would have expected + / GND or - / GND.
« Last Edit: 17:20, 25 October 19 by LambdaMikel »

Offline Bryce

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What's important, especially if you are using it to power things that are in need of repair, is a current limit. If the DUT (Device Under Test) has a short circuit somewhere, the last thing you need is a PSU that can pump endless current into it. Normally, when I connect up a damaged CPC, I'll limit the current to about 1.5A. That way, if there's a direct short somewhere, it won't fry the traces off the PCB.
Most PSU's are and should be floating. The negative is a negative and not connected to ground and that's how it should be. Most good bench PSU's will have a seperate 4mm post for GND which you can strap to the negative rail if it's really required (extremely seldom).


Bryce.

LambdaMikel

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Are you saying that in order to power a circuit / LED with it, one should use GND / + or - / +? The video suggested the latter. The instruction booklet was uncomprehensible (ChinGlish). The tutorial video suggests one should use - / +. Not sure what GND is for. I would have assumed that - / GND gives -V, and + / GND gives +V.

Offline Bryce

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You always use +/- to power anything. If however, you are powering a circuit whose rail NEEDS to be referenced to earth, then you connect the earth and - together (or the earth and + if it's a negative rail).

Bryce.

Offline Bryce

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Ok, put down that coffee for a moment, I don't want anyone to destroy their keyboard when they look at these...


Sooo... This is a PCB I built when I was around 8 years old. As described above, it's almost completely made of salvaged parts. I suspect the two bright green resistors (100K), the three transistors (BC108 as far as I can remember) and the battery clip were bought new. The PCB was a sub-board out of an old TV and most of the components probably came from the TV too. The other (older) electronics people among us will recognise that many of the resistors are the old carbon composition type from the 50's/60's (the brown ones) and that small value capacitors (the beige ones) are foil roll from about the same time (and 50 times bigger than they would be today). The LEDs were the channel indicator LEDs from the TV. On the back of the PCB you can see that I had scratched off the existing traces and made my own holes to facilitate that ridiculous spaghetti of wires. At the time, my entire toolset consisted of a small Antex soldering iron and an analogue multimeter. The holes were made with a small jewellers screwdriver.


This was an electronic dice. It worked, which goes to show that you don't need a pile of fancy expensive equipment to start off in electronics, you just have to want to do it enough.


Bryce.


(you can finish that coffee now).
« Last Edit: 11:22, 27 October 19 by Bryce »

LambdaMikel

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Do you think you can get it going again?  :) So, given 2 GBPs per Transistor, you spent a lot of pocket money on it, right?

 

Offline Bryce

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If I could find my schematic. I remember that one of the chips was CMOS decade counter, but I don't remember what the other one was. Probably some other CMOS logic. From what I remember, the circuit basically counted from 1 to 6 extremely fast (multiple times per second) and the "randomness" just came from how long you held the button down.

Bryce.

LambdaMikel

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... If however, you are powering a circuit whose rail NEEDS to be referenced to earth...
I suppose that is never or very rarely the case with electronics devices, or? What would be an example for such a device?

Offline tjohnson

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« Last Edit: 15:15, 06 November 19 by Gryzor »

Offline Bryce

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Some options in the UK for a reputable supplier, one is the same as posted by Bryce under a different nam .

Well cheap bench psu


https://cpc.farnell.com/duratool/d03233/power-supply-1ch-18v-3a-adjustable/dp/IN0800087?ost=IN0800087&ddkey=https%3Aen-CPC%2FCPC_United_Kingdom%2Fsearch

Bit more money but more capability
https://cpc.farnell.com/tenma/72-10480/power-supply-1ch-30v-3a-adjustable/dp/IN06822

Triple output

https://cpc.farnell.com/tenma/72-10505/power-supply-3ch-30v-3a-adjustable/dp/IN06825


Yeah, they are cheap but tested and certified, otherwise Farnell wouldn't sell them. So they will be decent quality, but having to set the current limit manually everytime would get on my nuts.

Bryce.

LambdaMikel

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I ended up getting this one for my return (it is linear) - Chinese I suppose as well, but I had good experience with SainSmart previously:


https://www.amazon.com/gp/product/B07V7CT1G7/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
It is linear, so far it is working great. It memorizes the last selection, and coarse / fine control is very useful.

Thanks for helping in the selection process.

Offline Bryce

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No problem. UNI-T are a known reputable low-cost brand. You shouldn't have any problems with it.

Bryce.

Offline 1024MAK

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Re: My first new Lab Power Supply started to burn after 5 minutes
« Reply #17 on: 22:46, 02 November 19 »
I suppose that is never or very rarely the case with electronics devices, or? What would be an example for such a device?
If there is a configuration or variation of how to wire up electrical or electronic equipment, you can be sure, someone, somewhere has used it.

All two wire electrical circuits work on the principle that current must flow from the generator / battery or other supply or source along one supply wire, through the device / circuit / load / appliance and then return back to the generator / battery or other supply or source along the second supply wire. This includes DC circuits and (normal single phase) AC circuits.

For a DC circuit / device / circuit / load / appliance as described above, on a bench power supply, the positive of the circuit connects to the bench power supply + positive terminal. The negative 0V / ground / GND connects to the bench power supply - negative terminal. The ground / earth / chassis terminal is then ignored.

However, some circuits use mains earth / ground, either because the circuit is a radio receiver, transmitter or transceiver, use mains earth / ground as part of their interference suppression, use mains earth / ground to help with shielding sensitive parts of the circuitry, or for safety reasons (typically any metal parts that the user can touch, and which may become live if a insulation fault occurs) if high voltages are used.

These circuits may have a separate earth / ground connection, or the 0V / ground / GND / negative connection may be intended to be connected to a supply where the supply 0V / ground / GND / negative connection is assumed to be earthed / grounded.

Very, very rare these days, but some very old equipment required the positive supply connection to be earthed / grounded (these mostly used ‘switched’ negative circuits).

The second possible reason for grounding one side of the circuit (as in the negative / 0V / ground / GND) side, is if you are using an oscilloscope with it. As most mains powered oscilloscopes reference their input to mains earth / ground.

A third possible reason these days, is to reduce the annoying tingle caused by the small leakage from class II double insulated equipment that uses a switch mode power supply unit (SMPSU). The class Y capacitors in such units allow a small current to flow from the AC mains to anything that is connected to earth, like YOU. By connecting the circuit 0V / ground / GND / negative to mains earth / ground, this current flows safely to mains earth / ground instead of using YOU to get back to earth / ground.

Have I driven you into the ground yet?  :laugh:

Mark



Looking forward to summer in Somerset :-)

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Re: My first new Lab Power Supply started to burn after 5 minutes
« Reply #18 on: 02:08, 03 November 19 »
Some options in the UK for a reputable supplier, one is the same as posted by Bryce under a different nam .

Well cheap bench psu


https://cpc.farnell.com/duratool/d03233/power-supply-1ch-18v-3a-adjustable/dp/IN0800087?ost=IN0800087&ddkey=https%3Aen-CPC%2FCPC_United_Kingdom%2Fsearch

Bit more money but more capability
https://cpc.farnell.com/tenma/72-10480/power-supply-1ch-30v-3a-adjustable/dp/IN06822

Triple output

https://cpc.farnell.com/tenma/72-10505/power-supply-3ch-30v-3a-adjustable/dp/IN06825
The second and third one are well cool, and cheap. Well, or at least cheap compared to those we need to order in the lab:
https://www.sigmaaldrich.com/catalog/product/aldrich/z742605?lang=en&region=GB&cm_sp=Insite-_-prodRecCold_xviews-_-prodRecCold10-2
It is not that I am paying them, anyway  :D
P.D: I think that the electronic dice is actually not so bad at all for an 8 year old kid!

 

LambdaMikel

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Re: My first new Lab Power Supply started to burn after 5 minutes
« Reply #19 on: 08:01, 03 November 19 »
Have I driven you into the ground yet?  :laugh:
Thanks for the thorough explanation!!Indeed, you GROUNDed me  :D

Offline Gryzor

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Re: My first new Lab Power Supply started to burn after 5 minutes
« Reply #20 on: 15:16, 06 November 19 »
Guys, I think nobody asked the main question: HOW IS THE  VFD PACMAN GAME? DID IT SURVIVE?

Offline Bryce

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Re: My first new Lab Power Supply started to burn after 5 minutes
« Reply #21 on: 16:31, 06 November 19 »
Guys, I think nobody asked the main question: HOW IS THE  VFD PACMAN GAME? DID IT SURVIVE?

Well most of us actually read the entire first post which included the sentence: "Putting back the batteries in the Pacman game - well, it still works!!!".
So we didn't need to ask. :)

 Bryce.

Offline Gryzor

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Re: My first new Lab Power Supply started to burn after 5 minutes
« Reply #22 on: 16:45, 06 November 19 »
Well most of us actually read the entire first post which included the sentence: "Putting back the batteries in the Pacman game - well, it still works!!!".
So we didn't need to ask. :)
 

Guess I'm impatient that way :D

Offline Patrick

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I just bought the PeakTech 6080 A (linear, 0-15V and 0-3A).
Elektor test here: https://www.elektormagazine.com/news/reviewthepeaktech6080alabpowersupply

Offline Bryce

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I just bought the PeakTech 6080 A (linear, 0-15V and 0-3A).
Elektor test here: https://www.elektormagazine.com/news/reviewthepeaktech6080alabpowersupply

That's a bargain for what it offers. It will be only good for digital stuff, but I assume you won't be doing any sensitive analogue electronics.
My only complaint wuld be that they use 4mm banana sockets instead of proper binding posts, but they could easily be changed.

Bryce.
« Last Edit: 14:40, 18 January 20 by Bryce »