Need help identifying the capacitor spec

Thread Starter

BarryTron

Joined Nov 18, 2018
89
My TV burned out, so i opened it up and the C311 capacitor looks like is dead. Googled the DELTA DPS-245BP schematics and all they have is an asterisk symbol next to the name. Would really appreciate if I can get some help identifying the capacitor spec.

cap.png
Thank you
 

Tonyr1084

Joined Sep 24, 2015
5,992
My TV burned out, so i opened it up and the C311 capacitor looks like is dead.
What makes you think it's dead?

Better to fully diagnose the problem before you start buying parts. If you just start buying and replacing parts soon enough you'll have a new TV for your remote.
 

kennybobby

Joined Mar 22, 2019
75
Looks like a HV snubber cap, the other one is likely blown to bits and unreadable. The * is likely to a note about selection. If you order might as well get two and replace both with fresh caps, and go for a higher voltage, e.g. 2kV or 3kV. Exact capacitance value is not critical but get both the same.
 

Thread Starter

BarryTron

Joined Nov 18, 2018
89
What makes you think it's dead?

Better to fully diagnose the problem before you start buying parts. If you just start buying and replacing parts soon enough you'll have a new TV for your remote.
Good question Tony,

Visually, the back of the cap is gone.

capback.png
 

Thread Starter

BarryTron

Joined Nov 18, 2018
89
Looks like a HV snubber cap, the other one is likely blown to bits and unreadable. The * is likely to a note about selection. If you order might as well get two and replace both with fresh caps, and go for a higher voltage, e.g. 2kV or 3kV. Exact capacitance value is not critical but get both the same.
I posted a picture, yes one is blown. My problem is that the schematic and my meter calls for a 331 capacitor, but the capscitor photo calls for a 221 capacitor. I don't understand which one is the correct only (is it possible to print wrong number on the capacitor?). And which one should I replace it with?
 

kennybobby

Joined Mar 22, 2019
75
Think about what purpose these caps serve to function--they are snubbers used to provide a bleed path for a high voltage spike at the front edge of an inductive kick (V=-L x dI/dt) when the FET switches off, so the most important aspect is the voltage rating should be as high as you can find.

The capacitance value is down in the 200-300 range of picoFarads because the time period "dt" is very short and the corresponding frequency for reactance calculations is very high. So any capacitance value in this range will be sufficient and they are typically available in standard values, e.g. 100, 220, 330, 470pF with 10- 20% tolerance. 221 or 331 (220-330pF) are essentially equal in this situation. Ignore your meter reading-- unless it is a precision LCR meter that can measure across various frequencies the tolerance variation will be too difficult to measure.

Unless the blown cap is reading as a short circuit, this was likely a symptom and not the cause of your issue. Check the Q302 FET and all the other fets and diodes in your schematic picture for damage. When a snubber blows generally something else goes too. Whether or not that cap is in the circuit would not be the cause for the unit to not power up--there is something else failed too.
 

Tonyr1084

Joined Sep 24, 2015
5,992
Good question Tony,

Visually, the back of the cap is gone.

View attachment 231197
Good answer.

I asked because sometimes people come here asking for help and believe they know what the problem is. They can end up spending a lot of money "Guessing" at what the problem is. I always suggest fully diagnosing the problem before replacing components. Another common warning I give is that you need to understand WHY the component (this case a cap) failed.

No joke! I've seen people replace a fuse over and over hoping that it's a problem with the fuse when in fact there is something else drawing massive amounts of current. I'm not suggesting that's your issue; just pointing out that not always are we dealing with sharp tools from the shed. But obviously from your picture - - - . Nuf said.
 
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