Hitachi P50V701 blowing capacitors

[c_hegge]

Re: Hitachi P50V701 blowing capacitors

The board markings are not damaged there. I can tell from that picture that both caps are installed in the correct polarity. It seems that there is a fault with the power supply which is over volting the cap. It does seem odd, though that the other cap doesn't blow up, since it appears to be in parallel with the one that does.

[R_J]

Re: Hitachi P50V701 blowing capacitors

Those look like c552 & c553 they are connected in parallel and are for the +90 volt supply. How much voltage do you measure on CN64 pin 8,9 or10 to ground? That should be the vs voltage, you said you measured 86 volts which is close enough and not over voltage.
You may want to check d550, d551 and d552 make sure one of them is not shorted suppling ac to the caps. but I dought that. What value cap are you installing?
There is a lot of protection on these supplies to protect with over voltage etc.
(vr380) VS1 is the adjustment for VS voltage

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

First off, thanks so much for everyone's help so far. The caps are 100v 3300uf. I checked the components that you mentioned and none were shorted. I bought the caps off of amazon.com. I read the reviews of people that had purchased them before. One person said that they installed the cap and it blew 4 minutes later. I would be inclined to think that I just got some bad capacitors, but this is the second one that has blown in the same spot. Both caps were from the same seller though. It just seems odd that only the one cap is blowing. I think I might just put the board in and see if the next one blows too. I guess that's really the only option left. I checked the x and y boards and nothing seemed out of place. I would think that if either of those boards had a problem, then the tv would show symptoms when it powers up, but the screen is clear with no lines, sparkles or any other distortion. What do you guys think? I'm nervous because that cap popped like a rifle.

[Agent24]

Re: Hitachi P50V701 blowing capacitors

The sleeve length on the capacitors don't match up, which seems unusual for a good quality capacitor company like NCC, they should have better quality-control.

Maybe they are fake...

[Shinju]

Re: Hitachi P50V701 blowing capacitors

Or don't bother puttng in that other possible crappy cap and just get a quality cap and try.

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

Where is the best place to buy caps?

[Shinju]

Re: Hitachi P50V701 blowing capacitors

Digikey or mouser.

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

okay thanks

[freakaftr8]

Re: Hitachi P50V701 blowing capacitors

sounds like crappy caps to me too. that cap along with the other one that's original are wired in parallel which means that if one goes the other one could be bad too. With that blown cap out of circuit and the good one still in circuit measure across the two leads and make sure you don't have a 0 ohm short before installing a new one. Although I'm pretty sure your power supply is OK.
but if I were you in your going to order well known good capacitors from a well known website. I would order both that are in that circuit even though the good one hasn't blown doesn't mean that its not causing a problem or it has been severely strained by blowing the other cap

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

The two capacitors are the same in that circuit. I bought 4 of them from mouser. I will update this once I install them and see what happens.

[ibgm]

Re: Hitachi P50V701 blowing capacitors

I worked on a power supply one time and noticed when I removed the caps that the polarity marking on the circuit board was wrong! I always use a sharpy to mark the negative when I remove them. I've only seen that one time. Try and find a good picture of the board somewhere and see if you can confirm the polarity. Try E-Bay or any of the other sellers, I'm sure you can find a decent detailed picture somewhere. Good luck and keep us posted. I'm sure that must have sounded like a cannon when that went off! I would be on the other end of a 50 foot extension cord with this one!
oops! sorry I missed the earlier post where the polarity mount down was confirmed. If I could delete this I would.

[freakaftr8]

Re: Hitachi P50V701 blowing capacitors

50 foot extension cord. ..I love it. Think we have all been there once!

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

caps are installed and the tv is working. It's been on for 25 minutes and no bangs. Lesson to be learned? Do not buy cheap parts!!!

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

Tv has now been on over an hour so I feel confident in saying that it's fixed. Thanks guys for all the help.

[freakaftr8]

Re: Hitachi P50V701 blowing capacitors

Good to hear!

[Shinju]

Re: Hitachi P50V701 blowing capacitors

Heck yes! I am glad you got her up and running!

I wish I knew why my VA/VS voltages are almost double of what they should be.

How is the picture on yours? Notice any maldischarge sparkling?

[Shinju]

Re: Hitachi P50V701 blowing capacitors

Also don't forget to retake and adjust your voltages VA/VS with a solid white screen with dynamic setting and 100 contrast after 20min of use.