Thank you so much R_J, indeed the transformer is not the issue. But we have worse problem now as the IGBT and rectifier diodes keeps blowing when the setpoint of the HV output is around 52KV. Maximum voltage is supposed to be 80KV.

I have here some sketched circuit diagram for you to refer to. Maybe someone can help us solve this problem. We have tried to replaced the affected parts including the PWM IC and OP-amps but still encountered the same burnt parts.

Is there any chance that the big capacitors are the issue?

[ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3530258}[/ATTACH][ATTACH=JSON]{"data-align":"none","data-size":"full","title":"image.png","data-attachmentid":3530259}[/ATTACH]...

Hello All,

i would like to post an interesting topic regarding 3-phase stepdown transformer which we suspect to cause an overcurrent (138A) which resulted to power tripped off of the HV power supply (80KV output).


Problem statement: Power tripped Off

Initial Problem: Found 2 IGBT and 2 rectifier diodes shorted (burnt).

Action Done:
1) Replaced the faulty parts with good spare.
2) Measured impedance of the 3phase input lines and found that L2 to L3 has 23.3ohm while other pairs are 51Kohm. This pins will...

Hello [USER="57756"]R_J[/USER] and [USER="123007"]kasfamily[/USER] thank you so much..I will post it in a new thread..i will add some update as well.R_JHello [USER="57756"]R_J[/USER] and [USER="123007"]kasfamily[/USER] thank you so much..I will post it in a new thread..i will add some update as well.kasfamily

Hello All,

I was trying to post a new thread but i couldn't find the button for a new thread.

Anyway, i would like to post an interesting topic regarding 3-phase stepdown transformer which we suspect to cause an overcurrent (138A) which caused the High voltage power supply to tripped off.


Problem statement: Power tripped with inrush current of 138A.
Initial findings: low ohm L2 to L3 input voltage (25ohm)
Defects: IGBT and Diode shorted

Question: is this a normal resistance reading for the transformer at L2 to L3 reading? [TABLE="width:...

Hello [USER="57756"]R_J[/USER], attached herewith is the photo of the board.




[ATTACH=JSON]{"data-align":"none","data-size":"large","data-attachmentid":3294317}[/ATTACH]R_JHello [USER="57756"]R_J[/USER], attached herewith is the photo of...

Thank you so much guys!
To make things clear, I attached herewith the images of the faulty diode (channel 1) versus the good diode (channel 2).

[ATTACH=JSON]{"data-align":"none","data-size":"custom","height":"409","width":"1126","data-attachmentid":3290642}[/ATTACH]...

harp[USER="414449"]harp[/USER] thank you so much! Will try your suggestion out😇 by the way, is there any risk if i use the 1N4148 directly and test the unit at the machine?

lotas[USER="169795"]lotas[/USER] yes, i removed it already and measured stand alone. Also have tried to inject voltage to check if it is a normal diode or zener diode. But it seems that it is a normal diode because the voltage drop i read versus the voltage supplied is still...

Hello Everyone,
I have 1 diode on a circuit that I suspected to be faulty because the forward and reverse bias has a voltage drop reading.
While compared to the reading of another diode from the next channel it won't read at reverse bias.
Now the problem is; it does not have any body marking.
So I tried to sketch the diagram and found out that it is connected to the base and collector of the C3632 transistor.
What do you think is this diode?
Can you please suggest what part number can i use to replace this faulty diode instead?

Hoping that you...

Re: UV LED Device Repair

Hello All,

One more problem is that i could not remove it using 2 soldering iron and even with the use of low temp soldering lead..

Also, tried to use a hot air blower but all unsuccess to remove.

And to make things worse, it is so fragile that even poking slowly by a tweezer, it breaks!

Any suggestion on this?...

Re: UV LED Device Repair

Hi harp, really sorry for the very late reply. Been to other more urgent projects. Anyway, i have a photo attached here. As for your suggestion, i will try to do it. Thank you so much!

Hello eccerror, i couldn't identify if its parallel or series but the unknown devices (black color) are all open reading....

Re: UV LED Device Repair

Hi stj, sorry for the very late reply..

I measured the unknown component using diode mode but there is no reading at all even forward and reversed bias. So do you think it is a special device instead of a diode?

Re: UV LED Device Repair

Hello stj, yes, the leds are in series.

What is the best way to check this unknown component?

Hello Guys,

Part Name: UV LED 365nm
Problem Statement: LED intensity low

I am repairing a UV LED lamp device. Found to have multiple burnt devices though I cannot identify what is this. Highly suspect that it is a resistor or a diode but i could not fully identify it because both resistance and diode test got OL result.

Is there anyone here who knows what is it? or how can i test it?...

Hi Guys!

I am a beginner in electronics repair. This time I tried to repair an SMPS power supply with 4 outputs 24VDC (10A), 5VDC(10A), 12VDC (4A) and 12VDC (4A) due to intermittent power on/off. After series of checking, I found some few capacitors with high ESR and replaced those with good spares. Now the power is stable and output voltages are all good. But whenever I load test atleast 2A, the voltage drop on outputs 5VDC, 12VDC, 12VDC respectively. The original 5VDC when there is a 2A load becomes 1.3VDC, and the 2 outputs with 12VDC becomes 5.4VDC. However, when I load 8A on...

Re: Unidentified Capacitor

hi rj and stj, I already install the capacitor X7R series MLCC capacitor to replace the obsolete AVX cap. And guess what, my PS already can power up normally and with load test pass! Thanks guys for helping me out! Cheers!!!...

Re: Unidentified Capacitor

hi stj, thanks for your idea..anyway I tried to buy the mlcc cap with 220nF/630V rating because I cannot find the exact part online.. I will inform u guys later whether pass or fail after I install the part and do the testing.

Re: Unidentified Capacitor

Hi RJ, ok I will try your suggestion. Thanks a lot!

Re: Unidentified Capacitor

Hi RJ, I guess so..I'm still waiting for AVX's reply on my inquiry email. Still hoping they will reply by this week.