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Old 04-26-2020, 03:17 AM   #1
Hombre
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Default Schneider ABL8RPM24200 24Vdc 20A supply

Hi guys

I got this power supply that is damaged. No history behind it. Power supply has two separate inputs, 110V and 230V, could be that somebody connected it to the wrong input.

Upon opening i could see that Q11 5N80 is blown, and also MX6 UC3843 blown. On further checking diodes CR11 and CR12 (both U1D) are shorted, also diode CR19 BYV26E. Also the fuse from the DC line that is coming to this part of power supply.
Unfortunately when i was taking out the white glue from PCB i damaged diode CR46. Well i am not sure which one is it. It's connected between VCC and GND on UC3843. I installed there 1N4148, hopefully that's ok?
I have disconnected primary part of the power supply that it seems that is working properly without rest of circuits, It's giving out 332V and 166V between GND and 2 positive DC lines.
This 332V is going to the second part of the circuit, and among the other things is going through the 150k resistor to the VCC for UC3843. I am getting 8V after that resistor.
After all those parts are replaced and when i connect it to mains (230V) the FET 5N80 starts to heat a lot, so i have to unplug mains immediately.

Output of power supply tested by regulated power supply, connected 24V and current draw was around 40mA.

So i assume something around this PWM circuit is not working properly, but have no idea what, FET not driven properly? What it could be?
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Old 04-26-2020, 04:27 PM   #2
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Is the problem in the power supply primary
Or
Is problem in the power supply secondary
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Old 04-26-2020, 08:41 PM   #3
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Quote:
Unfortunately when i was taking out the white glue from PCB i damaged diode CR46. Well i am not sure which one is it. It's connected between VCC and GND on UC3843. I installed there 1N4148, hopefully that's ok?
I suspect the diode between VCC and ground is a zener diode NOT a regular diode Likely around 18v zener. for external protection
Are you sure CR46 connects to ground? or does it connect to the transformer?
Are you sure that is the correct number for the ic, as it's top is blown off

Last edited by R_J; 04-26-2020 at 09:28 PM..
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Old 04-26-2020, 08:50 PM   #4
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

I wonder if there is still a marking on the diode? Having a signal diode there doesn’t make any sense to me. A zener diode, as RJ said, has my vote too. Probably one side of the diode goes to ground. Question is now what voltage the zener needs to be?
UC3843 has a Vcc of like 8V or so.

Last edited by CapLeaker; 04-26-2020 at 08:55 PM..
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Old 04-26-2020, 09:00 PM   #5
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

It needs at least more than 8V to start and no more than 30v
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Old 04-28-2020, 09:57 AM   #6
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Assumed it should be zener, but had no idea which value, but still installed 4148
Now i have installed 18V zener there. So as soon as PSU is connected to mains, FET starts to heat up.
Tried with 7.5V zener, nothing happens because the voltage is 7.5V with that one so it does not turn on UC3843. And i am quite confident that it should be 3843 because i found blown top from ic, and could read most of the numbers. And also voltage of 8V is suggesting that it should be UC3843. But please correct me if i'm wrong.

On the Vref to GND - 0.5V
Vcc to GND - 7.9V (from 330Vdc line after a 150k resistor, checked that one out and is measuring fine)
Vout to GND - 0V

Tried with new UC3843 - no changes.

Edit:
Ok, so connected UC3843 to lab supply. It turns on at 8.3V, and off on 7.4V (I can see it with the current draw jump from 0 to 20mA and vice versa). So if i understand it correctly that is the reason that id does not start with those 7.9V that is getting from 150k resistor on 330Vdc line. So, maybe the voltage after rectifier is not correct, should be higher? That would also explain only one 450V cap tin complete supply hat is exactly on this line.

Thanks in advance for any tip

Last edited by Hombre; 04-28-2020 at 10:36 AM.. Reason: Added new info
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Old 04-29-2020, 05:30 AM   #7
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

The typical startup voltage on Vcc is 8.4V, you got 8.3V... so that is within spec. Maybe the 150kOhm start resistor has gone higher in value. How much DCV do you get on the 450V capacitor? You should have like 400V when the PFC is on. The PFC has to work, other than that there wont be anything on the secondary.
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Old 05-01-2020, 06:32 PM   #8
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Unfortunately this 150k resistor is within spec, measured 149.5k, so quite close.
My limited knowledge tells me that there is no PFC IC on the board.
There are 5 IC's beside UC3843. All those IC have a common voltage, which is not present on start up. Injected 8-12V there and no significant power consumption, around 30-40mA, depending on voltage, which suggests that there should be no sort on IC's supply line.
So there is LM2903, comparator that should switch on the relay (12Vdc) on the primary side. When mains is plugged in there is around 2.1V on 2 outputs of the LM2903.
HFC4013 and HFC4081 dual flip flop and quad 2 gate and.
IR2110, mosfet driver for 2 pieces of 40N60 fets.
And one more UC3843 in conjuction with IR2110.
Assume this other supply should be around 12V but have no idea where from does it come.

Any other idea what could go wrong, and especially why fet is getting very hot in matter of seconds?
I appreciate your time, thanks
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Old 05-08-2020, 02:42 AM   #9
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Tried with lower ohm value resistor so instead of original 150k i installed 120k ohm resistor. No change in voltage, 7.8V just like with the 150k ohm resistor. And in matter of seconds fet starts to heat up.
Any idea why?
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Old 05-09-2020, 09:15 AM   #10
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

is the driver for the fet stuck on? or the fet itself shorted / leaky?
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Old 05-10-2020, 12:13 AM   #11
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Tried with the new ones, same story happening, i will try to investigate it a bit more, although have no idea what next, but will not give up
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Old 05-10-2020, 04:13 PM   #12
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Did you replace CR11,CR12 & CR19 with the same part numbers? When you checked them did you check them out of circuit? CR11 & CR12 are across R64 which is 4.7Ω
CR46 is very likely a 18 volt zener diode, if you only get 7.5v then the uc3843 could be bad or something that is connected to CR21 anode side could be loading it down.
Also that VCC line should connect to CR22 cathode, this is the voltage that keeps the ic running once it starts. The transformer has a secondary winding that likely connects to R83/R84 that then connects to CR22 anode. This is where the ic gets the vcc from once the circuit starts running.
Here is a circuit that uses almost the same ic.
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Last edited by R_J; 05-10-2020 at 05:04 PM..
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Old 05-11-2020, 05:51 AM   #13
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Hi, thanks for the schematic, looks more or less the same as the circuit.
CR11 and CR12 where shorted, both of them are U1D, replaced with the same ones. Yes, R46 is 4.7ohm, it's not burned or open.
CR19 is a BYV26E, thought it's shorted but of the circuit measured fine, but replaced it with the new one just in case.
As suggested, installed 18V zener in place of CR46.
Tried new UC3843, same thing happening, not getting 8.3V that are necessary to turn on UC3843, voltage is always 7.8V.
And yes, on CR21 anode there is Vcc for another IC's: U3843 (another one), IR2110, LM2903, HCF4013, HCF4081. Tried injecting 12V there, no shorts, consumption of all those circuits around 50mA.
On the secondary winding of transformer (Na on the schematic - auxiliary) i don't have any voltage, could be that it needs UC3843 to turn on to get some voltage there. Winding is not open, it looks ok. Cathode of the CR22 is connected to this secondary of the transformer.
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Old 05-11-2020, 06:08 PM   #14
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

The cathode of CR22 should not be connected to the secondary of the transformer, it should be the anode that connects to the transformer. CR22 is similar to the Dbias diode in the schematic.
The ic should be outputing pulses to drive the mosfet's gate, at high frequency. the mosfet switches the primary winding at high frequency which induces voltage in the two secondaries, the main secondary supplies the standby voltage for the main power supply and the aux winding supplies the run vcc voltage.

Last edited by R_J; 05-11-2020 at 06:13 PM..
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Old 05-11-2020, 08:29 PM   #15
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Quote:
Originally Posted by R_J View Post
The cathode of CR22 should not be connected to the secondary of the transformer, it should be the anode that connects to the transformer. CR22 is similar to the Dbias diode in the schematic.
My bad, you are correct, it is anode.

I installed new UC3843 (from ONSemi) and now voltage is 8.00V, but unfortunately that's still 0.3-04V to low to turn on the IC. Obviously something is pulling it down but so far i could not find the cause for this behavior.
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Old 05-12-2020, 05:43 PM   #16
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Not giving up

So, I did the measurements on UC3843
First - Mains connected, power to IC provided from 330Vdc line over 150k resistor, with the consumption of 2mA.
1- 1.2V 8- 0.7V
2- 0.17V 7- 8V
3- 0 6- 0.04V
4- 0.38V 5- 0

Second measurement - 8V injected with lab supply and IC turned on (interesting thing is that sometimes IC turns on wit as low as 8V)
1- 6.8V 8- 5V
2- 0 7- 8V
3- 0 6- 4V
4- 2.1V 5- 0
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Old 05-12-2020, 05:55 PM   #17
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

How do you know the ic is working? did you connect a scope and look at the output? The ic has an internal protection zener diode of 36v so the only other form of regulation on that line will be the external zener diode (18v) with the 18v zener in place and the ic removed you should have 18v on the vcc line. (don't connect the ac without at least the 18v zener in place)
The vcc will not likely get higher than 8 volts untill the circuit works and the transformer supplies the run vcc of around 18v
Is that 100f 50v capacitor on that vcc line ok?
If the ic is working and outputing a prober drive signal to the fet, it is possible the transformer has a shorted winding, this would cause the fet to get hot.
That transformer does look a bit burnt, or is it just from residue from the blown fet. Although rare, it is possible it is bad.

Last edited by R_J; 05-12-2020 at 06:12 PM..
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Old 05-13-2020, 04:19 PM   #18
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Well, as i don't have scope my only option is multimeter and lab supply. So with 8.4V the output activates and it's active until voltage drops under7.6V. so based only on that fact i was sure that IC is good, and also changed 3 of them, could be that all 3 are f up but...
So, I did a test that you suggested, took out IC and the voltage is 18.3V, regulated by CR46, 18V zener.
Cap also tested, it is ok, same happening with the new one.
Yes, transformer indeed looks burnt but it is mostly only the top protective layer, when i peel it a bit it does look clean. Although it is just across of the fet that blown, so as you said there is a chance that transformer is shorted . I can't test it with anything else than multimeter unfortunately, and i can tell you only that all 3 windings are not open. Shorted, maybe, but hard to know without some proper instruments.
Damaged transformer is the worst outcome i would say because of transformer availability on the market and also unknown exact spec of the transformer.
But i have found one that could work as a almost direct replacement - attached pdf (74202).
Secondary is going to LM317 which is then powering LM224. When i connect 24V to the output of the PSU there is 6V on Vcc pin of LM224. (7.7V on input pin of LM317).

To be honest i have no idea what else to test except the transformer, and that one is not that easy to test, unfortunately.

Thanks for your help
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File Type: jpg IMG-4065.jpg (579.8 KB, 9 views)
File Type: jpg IMG-4064.jpg (613.3 KB, 9 views)
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File Type: pdf 74201-74202-Datasheet.pdf (127.6 KB, 4 views)
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Old 05-13-2020, 04:44 PM   #19
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Default Re: Schneider ABL8RPM24200 24Vdc 20A supply

Quote:
So with 8.4V the output activates and it's active until voltage drops under7.6V
explain output activates? the ouput should be a high frequency waveform (50~100khz). if all it does is supply a dc voltage then all it will do is turn the fet on hard and it will heatup.

The ic should normally operate with about 15 volts for VCC

Last edited by R_J; 05-13-2020 at 04:59 PM..
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