Samsung LE40C750R2K capacitor on PSU blew up when unplugging inverter board

[Kairi]

Hi guys,

So I was messing with the power board to my Samsung LE40C750R2K TV whilst I was waiting for the main board to arrive and in hindsight was probably a stupid idea but I hadn't anticipated for what actually happened.

I had the power board connected the the inverter board only and switched on the TV. The backlight came on. I then unplugged the the cable connecting the power board to the inverter board (CNI801) and as soon as I did this, the blue capacitor (CI826) next to the connector starting sparking and smoke came out from it, and was especially violent at the solder point. This capacitor connects directly to ground so I guess as soon as the load was removed, the electricity could only flow through the capacitor and blowing it in the process. The cap does have a marking of 82J and 6KV which I assume can withstand 6000v

Does anybody who is more electronically savvy than me knows what may have happened here? I have plugged in power boards into the mains without anything connected in the past but nothing has happened. My logic would assume that if I unplugged the inverter board, the screen just wouldn't light up, it shouldn't blow a capacitor rated for 6kv.

I can replace this capacitor without problem but I just want to know if there's a chance that by unplugging the inverter cable, something else could have fried on the board.

The power board is BN44-00341A

Thanks

[R_J]

Unpluging the load with power on caused a spike that could have been 10-20kv or more, likely the cap is the only problem, you will find out after you replace it if the rest of the circuit still works.

[tvtimmy]

You should be ok with just replacing the capacitor.

[budm]

So you disconnect the cable on CNI801 while the backlights are on?
You have Power supply/inverter board combo., that HV connector CNI801 goes to the Balancer board.

[Kairi]

Originally Posted by budm

So you disconnect the cable on CNI801 while the backlights are on?
You have Power supply/inverter board combo., that HV connector CNI801 goes to the Balancer board.

Yes that's precisely what I did. The board that CNI801 connects to has a lot of mini transformer in the same style as the 2 big ones on the power board. This may very well be the balancer board you're talking about, I'm not 100% certain of the terminology but it powers the backlight.

What I'm intrigued about is why the surge happened only when I unplugged it whilst it was on, but nothing happened when I powered the PSU alone to check for voltages.

[budm]

The arcing Voltage can be really high.

[Kairi]

I replaced the capacitor and the power board appears to be fine. The backlight still works but I'm sure as hell I won't be disconnecting any leads with the power on anymore.

Interestingly, I checked the capacitor with a components tester and it was reading fine. A quick check with a multimeter also shows that there's no shorts in it.

[budm]

Never good idea to disconnect while TV is ON, especially the High Voltage, You are lucky you did not get shock from that connector (>3000V).

[R_J]

It could be that the cap. arced internally but did not short or effect it's capacity, but it could arc and short out even with a couple thousand volts across it now.

[sean0118]

The output of the power supply probably has high inductance, once you remove the load the current through the inductor will continue to flow causing the voltage to rise sharply.

Some power supplies, like flybacks in CRT TVs use this to generate very high voltages.

But in your case the voltage got high enough that it found a path through that capacitor.

[Kairi]

Thanks for the explanation and bring to me the awareness of the dangers messing with the inverter. Luckily I didn't get a shock and have dodged a bullet this time.

PS board, inverter and the main board that arrived this morning, works fine. I've not plugged it into the T-con yet, and I'll make another thread about that in regards to possible risks of plugging this on since this TV has an unknown history.

[R_J]

On the secondary of the inverter transformer you would'nt have received much of a shock, but the high voltage at high frequency arc will burn you, and it will hurt.

[budm]

https://assets.shopjimmy.com/media/c...341a-top_1.jpg
It is rated at 1000V 180mA as printed on the board, the firing is proBably about 3000V. I think it will hut quite a bit.

[nomoresonys]

That would probably hut LIKE HELL.

[Jimmy1979]

Originally Posted by Kairi

Hi guys,

So I was messing with the power board to my Samsung LE40C750R2K TV whilst I was waiting for the main board to arrive and in hindsight was probably a stupid idea but I hadn't anticipated for what actually happened.

I had the power board connected the the inverter board only and switched on the TV. The backlight came on. I then unplugged the the cable connecting the power board to the inverter board (CNI801) and as soon as I did this, the blue capacitor (CI826) next to the connector starting sparking and smoke came out from it, and was especially violent at the solder point. This capacitor connects directly to ground so I guess as soon as the load was removed, the electricity could only flow through the capacitor and blowing it in the process. The cap does have a marking of 82J and 6KV which I assume can withstand 6000v

Does anybody who is more electronically savvy than me knows what may have happened here? I have plugged in power boards into the mains without anything connected in the past but nothing has happened. My logic would assume that if I unplugged the inverter board, the screen just wouldn't light up, it shouldn't blow a capacitor rated for 6kv.

I can replace this capacitor without problem but I just want to know if there's a chance that by unplugging the inverter cable, something else could have fried on the board.

The power board is BN44-00341A

Thanks

Hello

What was the value of the capacitor?
I have the same problem.
Was is 82j 6kv
Or B2j 6kv?
Thanx

[lotas]

Originally Posted by Jimmy1979

Hello

What was the value of the capacitor?
I have the same problem.
Was is 82j 6kv
Or B2j 6kv?
Thanx

Most likely 82pF 6kV.

[vinceroger69]

6kv 47pf
https://elektrotanya.com/samsung_bn4...wnload.html#dl

[Jimmy1979]

Originally Posted by vinceroger69

6kv 47pf
https://elektrotanya.com/samsung_bn4...wnload.html#dl

I found that service manual too but I don’t know if it’s the same.
I have a Bn44-00341a

The number on manual is not same.

[vinceroger69]

Originally Posted by Jimmy1979

I found that service manual too but I don’t know if it’s the same.
I have a Bn44-00341a

The number on manual is not same.

no its a b revision service manual, but should be the same cap in my opinion, its in the exact same position next to the connector with the same board location number its the only 6kv cap on the schematic so makes sense too

[Jimmy1979]

Originally Posted by vinceroger69

no its a b revision service manual, but should be the same cap in my opinion, its in the exact same position next to the connector with the same board location number its the only 6kv cap on the schematic so makes sense too

I will order one 47pf 6kv and test it out.
If it goes Lucy in the sky then i know it’s not good or other problem.
Thank you for your help👍🏻