Hi guys. I am new to electronics having just retired. Unfortunately I had an accident whilst removing a component from a Z-Sus board in a plasma TV. The component I destroyed, I think, is an SMD capacitor. I measured it and it fits into the category of an 0805. There are no markings so how do you know the capacitance, voltage, wattage etc? It has an ESR of 1.5 ohm. I bought a SMD tweezer DMM but it wont measure nf. and I can't find a schematic for this board anywhere. Its from an LG 42PX5D. Board number 6871QZH056B. Would really appreciate any info on this.

 

It has an ESR of 1.5 ohm.

I searched the Web and in this paper it has a graph of ESR vs capacitance value. See if it helps.

http://www.kemet.com/kemet/web/home...721E006EF53C/$file/Sun Paper on ESL & ESR.pdf

 

Hey, thanks for all your efforts with this. It's a step forward for me although I don't pretend to understand everything here, but I'll endeavour. Best wishes Robert

 

Doesn't the ESR depend on the test frequency and exact shape of the test waveform?

I really think to measure capacitance you should use a capacitance meter!

If you don't have a cap meter you could do something like use the cap in a 555 timer circuit (look at the freq on the 'scope) and compare to other test caps in that same circuit. It shouldn't take too long to work out its value.

 

Is this a ceramic cap? I will look to see if I can find a drawing on this unit. I have the manual if you will tell me what the designator is I can tell you the value.

Or I have the complete service manual if you want it.

 

Doesn't the ESR depend on the test frequency and exact shape of the test waveform?

I really think to measure capacitance you should use a capacitance meter!

If you don't have a cap meter you could do something like use the cap in a 555 timer circuit (look at the freq on the 'scope) and compare to other test caps in that same circuit. It shouldn't take too long to work out its value.

Thanks The R_B. As far as I understand the ESR does depend on the test frequency but I guess that test frequency is unique to the design of the meter and the ESR vs voltage scale is worked out accordingly. I'll have a go at what you suggest but even if I know the cap value, how do I know the voltage and wattage to specify when ordering. This capacitor is about half the size of an ant!!!

 

Is this a ceramic cap? I will look to see if I can find a drawing on this unit. I have the manual if you will tell me what the designator is I can tell you the value.

Or I have the complete service manual if you want it.

Thanks Jotto for this. I'm going to send you some photos of this capacitor. As I said to The_RB, it's about half the size of an ant. I think its ceramic and its black in colour. Does your service manual provide a schematic for the Z-Sus board? If so, I would be grateful for it. Appreciate your help. Robert

 

Hi
Here's a photo of the line of caps I am talking about. You can see I destroyed the last three. The all have the same ESR. Robert

 

They are connecting the ground plane.

They are likely 0.1uf caps to filter power supply noise.

Known as typical bypass or decoupling caps.