Hitachi P50V701 blowing capacitors

[KevinCro]

Hello All. I have a Hitachi plasma that is blowing capacitors. I have a picture of the capacitors attached. This is a new capacitor that I just installed. I replaced the y buffers and that allowed the tv to turn on and stay on. After the tv is on for a few minutes, the screen starts to fade and then boom!! Any ideas?

[budm]

Re: Hitachi P50V701 blowing capacitors

Voltage is too high, or wrong polarity?

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

The new capacitors have negative black written on them. What does that mean? All the other labeling is identical to the original capacitors

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

Also, I'm afraid to test the board while the tv is on. That capacitor literally exploded. Is there a way to minimize the risk?

[budm]

Re: Hitachi P50V701 blowing capacitors

The new capacitors have negative black written on them. What does that mean? All the other labeling is identical to the original capacitors

It is polarized capacitor (positive leg and negative leg) so you have to make sure negative leg of the cap goes into the hole of the circuit board is for negative, positive leg goes to the positive hole on the board.
Remove the cap and show us good clear picture of where the cap goes to, there should be big white band close to one of the two holes on the board for the cap.
is this the first time you do the cap replacement?

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

This is the second time I've replaced that cap. The first cap almost blew as well, but I thought it was because i ran the tv for too long with the lower buffer board removed. The tv was probably on for 4 minutes or so. I found a picture of the board online and made sure that my negative leads were in the right hole. My guess is that there is a bad component on the ysus. I'll pull it and check it over. Thanks for the help.

[budm]

Re: Hitachi P50V701 blowing capacitors

If the cap is put in correctly then it must be the Voltage problem that caused the cap to blow like that.

[Shinju]

Re: Hitachi P50V701 blowing capacitors

I have this exact panel, and I have ran it without the lower buffer board for almost an hour testing voltsges and never blew a cap.

What are your va/vs voltsges?

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

I can't find the test points. Does this board have any? Again I am afraid to be very close to the board while it is powered.

[Shinju]

Re: Hitachi P50V701 blowing capacitors

I was using the va/vs on the harness to check. My voltages are way high but my DMM was found to be defective so I need to retake them with my new fluke.

http://assets.shopjimmy.com/media/ca...2202-top_1.jpg

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

The Vs Voltage was 86 and the VA was 62

[Shinju]

Re: Hitachi P50V701 blowing capacitors

Is that with both buffers running? how about just the top or bottom?

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

Those readings are with both buffers running. The first cap blew with the lower buffer removed. Since then, I have replaced both buffer boards. I tested the voltage at the connector on the x board. The voltages were a bit lower than what the panel sticker reads. Is it possible that a component has failed on the psu restricting the flow of the current and causing the capacitor to overload?

[aaronwt6]

Re: Hitachi P50V701 blowing capacitors

I wish I could offer some advice, but boy I bet that capacitor was loud. I've blown up some small ones but nothing that size. Even a 470uf at 35v can make one heck of an explosion.

I have one of those power supplies sitting here and double checked your polarity and it appears to be correct.

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

I've been studying the circuitry of the psu and the capacitor that keeps blowing appears to be directly downstream from an identical capacitor that is not blowing. Does this mean that the problem is downstream from the blown capacitor? Possibly on another board? I'm lost at this point.

[selldoor]

Re: Hitachi P50V701 blowing capacitors

WE really need good clear pictures - have you checked for solder bridges that might touch when heated and have you clipped the capacitor leads close to the board - make sure it is not shorting on anything. Are the caps from a reputable source- where?

[KevinCro]

Re: Hitachi P50V701 blowing capacitors

Here are some pictures of the psu.

[Shinju]

Re: Hitachi P50V701 blowing capacitors

If all else fails don't scrap it, coppel tv repair can repair the board. These are not cheap to find to replace.

I wish mine was readily available to help you with. It's kinda buried at the moment!

[tom66]

Re: Hitachi P50V701 blowing capacitors

Could it be a counterfeit capacitor? I've had them before, a 450V one that violently vented on me... it was a "Nihoncon" in exactly the same font as Nichicon!

[Ltank]

Re: Hitachi P50V701 blowing capacitors

When board markings are damaged and unable to see. Use your ohm meter and check each pad to chassis ground. Only one of the legs should be grounded and that's the negative lead