Questionable polymer on my Sharp LC-42SB48UT

[AcGeorgiegirl]

I know this is maybe a fluke, because they don't have vents for expanding like the wet caps do, but I've a psb with a polymer that definitely looks like it's top is domed up a bit, on a tv that doesn't reach 5v standby. It goes up to 1.8. I'm wondering can I replace this polymer with a regular electrolytic, and if so, should the uf or voltage be a different amount? I would have included a pic, but I couldn't get the "bulge" to show up with my camera, sorry.

[Diah]

Re: Questionable polymer on my Sharp LC-42SB48UT

short answer Yes, same uf but with 10% more voltage than polymer.

either its hardly to say from the top look of polymer. as all had curve top . best way took out and check.

[Alastair E]

Re: Questionable polymer on my Sharp LC-42SB48UT

Try it and see...
--Either work--Or not....

Poly caps dont tend to fail as regularly as std caps so would doubt thats the issue.

[AcGeorgiegirl]

Re: Questionable polymer on my Sharp LC-42SB48UT

Is it more probable that the psb's filter cap might be going bad? I don't have an esr to test, but thought about replacing it after trying the polymer.

[Diah]

Re: Questionable polymer on my Sharp LC-42SB48UT

Is it more probable that the psb's filter cap might be going bad? I don't have an esr to test, but thought about replacing it after trying the polymer.

in general no, but some lost contacts on its bed. just re soldering or heating them will be back to life

[Alastair E]

Re: Questionable polymer on my Sharp LC-42SB48UT

Doubt it, more likely stdby reg is working in burst-mode for some unknown reason, maybe leaky diode on its o/p or short on that rail in m.b. or no f/b loop due to dodgy opto or the controller chip itself.

[stj]

Re: Questionable polymer on my Sharp LC-42SB48UT

not 10%, you need the cap to be rated for atleast 150% of the voltage it will see.

a lot of people do stupid things with cap voltage ratings, you can get in big trouble if you dont know what is actually going to hit the pins.

[Diah]

Re: Questionable polymer on my Sharp LC-42SB48UT

not 10%, you need the cap to be rated for atleast 150% of the voltage it will see.

a lot of people do stupid things with cap voltage ratings, you can get in big trouble if you dont know what is actually going to hit the pins.

you miss understood, 10% more as actual voltage value, exp. 30 = 35 lol

[AcGeorgiegirl]

Re: Questionable polymer on my Sharp LC-42SB48UT

Doubt it, more likely stdby reg is working in burst-mode for some unknown reason, maybe leaky diode on its o/p or short on that rail in m.b. or no f/b loop due to dodgy opto or the controller chip itself.

Thanks, Alastair. Any chance of getting a bit of a workflow idea for testing/troubleshooting all those techie things you mentioned? I started trying to decipher what they mean, but I exhausted Google's abilities.

[stj]

Re: Questionable polymer on my Sharp LC-42SB48UT

you miss understood, 10% more as actual voltage value, exp. 30 = 35 lol

no, i understood and as an ex design-engineer i know that 10% is not enough overhead to deal with ripple for long.
you need 50% overhead or the cap will heat up.

[Diah]

Re: Questionable polymer on my Sharp LC-42SB48UT

no, i understood and as an ex design-engineer i know that 10% is not enough ....you need 50% overhead

well, the poly caps installed now days are all had 100% more as real current ,poly cap ex 12V line had 25 VC , do you really think how much more ..they will let them more life.. no.. they may fail to produce the real currents at once. 10% more mean as this example 12V line instead 25V cap enough whole life 35V cap.. sorry for any bad feeling you got.

[stj]

Re: Questionable polymer on my Sharp LC-42SB48UT

35v on a 12v line is good, it will have a higher current capacity.

[AcGeorgiegirl]

Re: Questionable polymer on my Sharp LC-42SB48UT

Doubt it, more likely stdby reg is working in burst-mode for some unknown reason, maybe leaky diode on its o/p or short on that rail in m.b. or no f/b loop due to dodgy opto or the controller chip itself.

Could you give me some explanation of your acronyms, possibly? I don't know what "o/p", "m.b", "f/b loop", and "opto" are referring to.

[stj]

Re: Questionable polymer on my Sharp LC-42SB48UT

o/p = output
m.b. = main board
f/b loop = feedback loop
opto = opto-isolator, usually part of a feedback loop

[AcGeorgiegirl]

Re: Questionable polymer on my Sharp LC-42SB48UT

Awesome, thanks! Very helpful.