BSIDE I8 4020 Lab Power Supply, repaired - Page 1
Forum section: electronics / testgear

author: cybermaus
author_rank: Frequent Contributor
timestamp: March 02, 2025, 07:51:24 am
content: I bought this a month or so ago. Mostly because occasionally I wanted to be able to get a bit more current.2 days ago it broke. Waiting for parts But while looking at it internally I discovered how it worked, and wanted to hear if these designs are usualFirst the good things:- It is very nice and light and small and silent.- It handles even prolonged 15 Amps quite well, or at least, with little noise or heat- Not a lot of noise and ripple. Even the hair-thin scope spikes are only 100mVOne minor annoyance- I wish the cursor for CV/CC setting would stay on a bit longer. And when you reactivate, comes back on the position you left it.Then the 1 big warning:While a good beefy power supply if you need some Amps, but it is*NOT*a good current limiting or short protected supply.So my more detailed findings- Large output capacitor buffer: 5x 3300uF totaling 16.600uFAlready when first using it, I suspected this. When moving to a lower voltage, it takes a long time for to bleed to the lower voltage.In my view the problem with a large buffer is the CC does not work properly. It will always first dump the entire buffer at unlimited amps.- The entire PSU is switched on/off primary side when you turn the output on/off !?Is that normal? There is a extra 5V mini-supply that feeds the brain, and when you turn the output on/off, the main board is switched on/off by relay at the 230V input. So input filter, capacitors, FET's, transformer, output diodes, output capacitors, all are switched off/on when you turn the output off/on. (Edit: actually, the FET driver circuit is switched off, indeed by relay at the 230V, but the diode bridge and primary caps stay connected and thus charged.)- The entire voltage and current are regulated on the primary side. Both CV and CC !?Or at least, I see no silicon on the secondary side, other then a very beefy TO247 diode pair.I cannot actually measure at the moment, as I am waiting for parts.- Are those last two normal for lab supplies?This is my main reason for this post. Not only to complain or to warn others, but I am curious.- Final bad finding: It brokeIt should be able to handle shorts. I had used it once for voltage injection at low voltage. And also used it a couple of times to test a wire, set it to 1V 5A and short the wire, see the voltage drop.But this time it was set to 12V 1A, and the leads accidentally rubbed. Probably many spikes, all bigger then 1A because of the 16.000uF, and the FET's/ICBT's blew up.Waiting for parts.

author: BillyO
author_rank: Super Contributor
timestamp: March 02, 2025, 09:25:19 pm
content: Hmm,I bought the 4020 version too, for pretty much the same reason as you - some extra current, but have not yet taken it out of the box yet. But if the bulk capacitors are on the output side, and the MOSFETS are on the primary side, how could their discharge current spike effect the MOSFETS?

author: cybermaus
author_rank: Frequent Contributor
timestamp: March 03, 2025, 05:28:21 am
content: Often its not the current. It's when the current stops, in combination with some inductors.There are some beefy filter coils, but I have to admit the are on the other side of the capacitors, so the shorted discharge current would not flow over them.So I am not entirely sure either. Maybe the diode is shorted too (could not measure in circuit) and the FET damage is secondary, due to the shorted diode over-amping it.To be safe, I ordered the diode (MUR3060PT) along with the FET's (FNX30S60F, replacing with NCE30TD60BF, hope that will work)Maybe I should add some beefy 500V MOV's to either side of the transformer, I am unsure if those are even fast enough.But my advise to you is: don't short the wires, especially not on more then a few volts.

author: flash2b
author_rank: Regular Contributor
timestamp: March 07, 2025, 05:50:28 pm
content: I have bought the I8305 version, which does not have the USB Serial. I want to add this myself, but I cannot find the software for this BSide I8 so I would appreciate it if someone could share this.A review of my device:https://chinese-electronics-products-tested.blogspot.com/p/bside-i8305-lab-power-supply-tested.html(I am NOT the author of this !!)

author: cybermaus
author_rank: Frequent Contributor
timestamp: March 11, 2025, 09:08:59 am
content: Fixed with the replacement FET:FNX30S60Freplacing withNCE30TD60BF. Not claiming they are the best or even a correct replacement, I mostly checked voltages and amps, so I hope they will last. Edit: In fact reading back specsheet, they seem to be quite wrong. I think I researched one option, and accidentally messed up notes and bought another one. It seems to work though. Checked 40 volts, checked 20 amps. Checked sudden disconnect and reconnect at 20 Amp load (un/re plugging cable to electronic load) Did not yet try full short. Building up courage.The chunky double diode MUR3060PT, when desoldered seemed OK. I replaced it anyway.The new diode had a slight higher 0.51V rather then the old 0.46V, but that's probably in manufacture margin.Does anyone know why they do not use Schottky for this stuff? Too slow? Not easy to make for high voltages? I will do some study.I also measured both sides of the split-winding transformer with my new kelvin-probe milliohm meter, and they seemed a reasonable but more importantly identical 30mO, so probably not shortedStill not quite sure how a short on the secondary causes the primary FET's to fail, other then overcurrent, butthatshould be protected. I guess I did learn not to consider this device short resistant.Quote from: flash2b on March 07, 2025, 05:50:28 pmNo software, sorry. Also there seems to be a serial to USB convertor. Which is also easy enough to substitute I guess.I took some images, one chip I cannot read, the other I cannot find. But honestly, with labels for V/G (Volt Ground) and R/T (Rx Tx) my guess is the most important part is where the wires are coming from on the main board, so I included that image too.I left the unreadable chip image as is (no shrink) in case someone wants to try and read it with brightness/saturation etc.Edit: I did find the π122U31It's an isolation module. It has isolated USB, that's pretty good for a cheap device. I usually usea external USB isolator donglefor such things.

author: flash2b
author_rank: Regular Contributor
timestamp: September 05, 2025, 09:40:35 am
content: Does anyone have the software that came with this BSIDE I8?I have searched anywhere, read that many CDs that came with the supplied PSU were broken and the vendor also does not have it on their website.I found someone that figured out the protocol (on Banggood) and shared it, but the link on Wetransfer is dead.I want to be able to write a definition for TestController for this PSU. Without de scpi commands or hex codes this is not possible.

author: Rnj
author_rank: Newbie
timestamp: October 05, 2025, 01:28:54 pm
content: I looking for the same information here. I need to find a PSU that allow control over serial to an automated tests bench. I found this model but there is few information available. If you discover the serial protocol please share it with the community.

author: flash2b
author_rank: Regular Contributor
timestamp: October 05, 2025, 02:00:27 pm
content: Yes, I hope someone will share it so we could re engineer the protocol. Or someone has the protocol previously shared in we wetransfer link on banggood, but link is expired.

author: BillyO
author_rank: Super Contributor
timestamp: October 06, 2025, 12:27:59 am
content: Quote from: cybermaus on March 02, 2025, 07:51:24 amFinally got mine out of the box. I did not find this. Current limiting seems to work fine, it handles shorts and has a fully functioning OCP function. Maybe yo got a lemon?Is yours working better after the repair?

author: BillyO
author_rank: Super Contributor
timestamp: October 06, 2025, 12:50:59 am
content: Quote from: flash2b on September 05, 2025, 09:40:35 amHere.

author: cybermaus
author_rank: Frequent Contributor
timestamp: October 06, 2025, 05:13:48 am
content: Quote from: BillyO on October 06, 2025, 12:27:59 amWell, I urge caution. Mine also appeared to work OK when I tested it after I first got it. Dared to short it with no hesitation, just like I do on my other supply.Though even then I already noticed some bigger sparks then I was used to.When it broke, it was when Iaccidentally rubbedleads. Meaning many small connects and disconnects. I think that somehow pushed it.Maybe my replacement FETs are better, maybe not. Maybe you have better FET's, maybe not.Anyway, as much an issue as the fact it broke, is the bad CC response. Do this please: Set CC to lets say 1A and CV to 12V. Take a 0.1Ohm resistor. Hook a scope over the 1 Ohm resistor and hook it to the supply.You will see a 120Amp spike. This is true for all power supplies, but this one takes longer and is more energetic then what I was used to. Specifically, this one has 16000 uF worth of energy.And because this is a consequence of the core design, the way they drive & control both output current and output voltagefrom the transformer primary side, I do not think I "had a lemon"This design is very well suited for a small, efficient, lightweight, high current capable, power supply. They also managed to get it remarkably precise when a stable load is applied. But the design is not well suited for fast response times, not in voltage and not in current. In my (admittedly non-pro) view at least.

author: BillyO
author_rank: Super Contributor
timestamp: October 06, 2025, 02:00:59 pm
content: This is an SMPS, so of course both the voltage and current control are implemented on the primary side. That's how they work. To implement them on the secondary (output) side you'd need linear circuitry for both voltage and current control. That would be... uncommon.

author: cybermaus
author_rank: Frequent Contributor
timestamp: October 06, 2025, 03:10:14 pm
content: The other supply I have only roughly controls voltage on the primary side, to some fixed 36V DC. And then there is an extra buck convertor on the secondary side that controls the actual set CV and CC on the secondary side. Making for much better response times.

author: BillyO
author_rank: Super Contributor
timestamp: October 06, 2025, 03:12:41 pm
content: Hmm, not seen that approach before. Well, every day is a learning day, I guess.

author: flash2b
author_rank: Regular Contributor
timestamp: October 06, 2025, 03:15:32 pm
content: Thanx for the software + doc.Is the word document your work, or from somewhere else ?

author: BillyO
author_rank: Super Contributor
timestamp: October 06, 2025, 03:16:29 pm
content: It's from the CD that came with the supply.

author: flash2b
author_rank: Regular Contributor
timestamp: October 06, 2025, 03:21:04 pm
content: i would not expected to support ModBus protocol. Well TestController supports that, so it can be done. I need to fit RS232 inside my unit first.