Toshiba 42DPC85 will not power on

[LongJohns]

First, to say Hi - stumbled upon this site only just recently and it looks like it is a wealth of information (don't know how I didn't find is sooner).

And on to business, I have a Toshiba 42DPC85 plasma with a chassis TAC 515 that does not power on. Front panel led blinks and the relays cycle a few times.

Replaced the capacitors (some had the usual bulging) and still nothing. I get no VSS power off the power supply. Found the service manual online (couple of different sources) but it does not seems to have the power supply diagram in the ones I found.

Can anyone point me in the right direction here?

Thanks

[LongJohns]

Re: Toshiba 42DPC85 will not power on

no suggestions or info on a power schematic?

[rayrod81]

Re: Toshiba 42DPC85 will not power on

This is a Sanken power supply so you will not be able to find a schematic. Check Z401, Z601 for shorts or low resistance readings and check the surrounding resistors and make sure the values are consistant with what they read on a meter. You will have to remove them from the board to get a true reading.

[bbjunkie]

Re: Toshiba 42DPC85 will not power on

Did you replace all capacitors, or just the bulging ones?

Capacitors can be bad without a visible bulge.

Also, did you replace them with low ESR capacitors?

[LongJohns]

Re: Toshiba 42DPC85 will not power on

This is a Sanken power supply so you will not be able to find a schematic. Check Z401, Z601 for shorts or low resistance readings and check the surrounding resistors and make sure the values are consistant with what they read on a meter. You will have to remove them from the board to get a true reading.

Thanks you for the info, will have a look in that area a bit later today and will post what I find (good or bad).

Did you replace all capacitors, or just the bulging ones?

Capacitors can be bad without a visible bulge.

Also, did you replace them with low ESR capacitors?

Replaced them all except for 2 of them that I didn't have on hand, but these seem to be in the 5v section which is working.

As for ESR - can't say for sure, most of the ones I order are from Digikey and most of the time they do not list a ESR rating, but have never had an issue with another tv I repaired or several monitors - but maybe I got lucky with those?

Thanks again for the help so far.

[LongJohns]

Re: Toshiba 42DPC85 will not power on

ok, here is what I found:

Z401 and Z601 are good
surrounding resistors are good

Ok, now the unit does seem to power on, I do get Vss for a brief moment but then the power supply shuts down - obviously detecting a fault someplace.

Any other suggestions?

edit: this is a plasma unit if that helps.

[retiredcaps]

Re: Toshiba 42DPC85 will not power on

As for ESR - can't say for sure, most of the ones I order are from Digikey and most of the time they do not list a ESR rating,

Impedance is the same as ESR.

If you pick a low ESR cap from digikey, it IS listed as impedance. For example,

http://search.digikey.com/us/en/prod...424-ND/2433558

If you pick a non low ESR cap, impedance is left blank. For example,

http://search.digikey.com/us/en/prod...80TB-ND/268465

[LongJohns]

Re: Toshiba 42DPC85 will not power on

Ok, what would we be looking at for a min 'good' value then?

Example, would this be considered a 'good' cap for this supply, http://search.digikey.com/scripts/Dk...ords=P11944-ND ? This is 1 that I used, will have to check the rest.

Is it, the higher the number the better?

[retiredcaps]

Re: Toshiba 42DPC85 will not power on

Example, would this be considered a 'good' cap for this supply, http://search.digikey.com/scripts/Dk...ords=P11944-ND ?

Panasonic makes good caps. This one is rated at 85C. I wouldn't use this in a plasma that generates a lot of heat.

See this recent thread (posts #1 to #6). It asks similar questions and I provided answers.

https://www.badcaps.net/forum/showthread.php?t=18382

[LongJohns]

Re: Toshiba 42DPC85 will not power on

Panasonic makes good caps. This one is rated at 85C. I wouldn't use this in a plasma that generates a lot of heat.

See this recent thread (posts #1 to #6). It asks similar questions and I provided answers.

https://www.badcaps.net/forum/showthread.php?t=18382

Ok, read through the info and that brings up another question, relating to the above posted capacitor 250uf 450v, the Capxon chart, doesn't go up to 450v. These 2 capacitors had an obvious bulge to them before they were changed - now it is quite possible that the ESR rating is higher that what was there originally, so now what? Do I just find a cap with a low ESR rating and install that, like this one: http://search.digikey.com/ca/en/prod...2793-ND/758005

edit - on a side note, I can heard a very high pitch 'buzz' (for lack of a better term) after the unit has gone into shut down protection - but I can't really seem to isolate the area, but if I had to guess, I would say it is in the Z401/Z601 area (basically the same area where the budged caps were).

[retiredcaps]

Re: Toshiba 42DPC85 will not power on

the Capxon chart, doesn't go up to 450v.

It is possible that Capxon chart is out of date or isn't published or you are not looking at the right series datasheet. Series is usually a 2 letter code like GL. If the big Capxon cap is not GL, but something else, then the GL datasheet won't list it. Capxon makes many series.

These 2 capacitors had an obvious bulge to them before they were changed - now it is quite possible that the ESR rating is higher that what was there originally, so now what? Do I just find a cap with a low ESR rating and install that, like this one: http://search.digikey.com/ca/en/prod...2793-ND/758005

In general, these big filter caps don't undergo the same stress as the other caps on the SMPS power board so ESR is a less important criteria.

So if you can't find the datasheet, just choose something from Panasonic, United Chemicon, Rubycon, or Nichicon. Again, the one linked above is another 85C cap.

[LongJohns]

Re: Toshiba 42DPC85 will not power on

ok, an update. Installed the recommended caps and still no joy, however the power supply relays are acting a bit differently, they turn on and then after some time 1 turns off. If I unplug the top connector on the board to the left of the power supply, the power supply will remain turned on. Toshiba calls this board a LOWB and that connector is just +24v and ground.

So it would seem to me that the supply is ok and there is an issue someplace else causing the shut down, this is where I currently stand...

[bbjunkie]

Re: Toshiba 42DPC85 will not power on

<pointless posting deleted>

[tom66]

Re: Toshiba 42DPC85 will not power on

This is a plasma so it doesn't suffer from 2 seconds to black.

There is probably a connector on the power supply which has a pin marked "VS ON". This switches on the sustain voltages (Vs and Va, and sometimes 5V to sustains too.) If VS ON is not on, look at the other rails - are they on?

[bbjunkie]

Re: Toshiba 42DPC85 will not power on

My error, that will teach me to read twice and reply once

[LongJohns]

Re: Toshiba 42DPC85 will not power on

This is a plasma so it doesn't suffer from 2 seconds to black.

There is probably a connector on the power supply which has a pin marked "VS ON". This switches on the sustain voltages (Vs and Va, and sometimes 5V to sustains too.) If VS ON is not on, look at the other rails - are they on?

Hi, thank you for your reply and this is what I have found:

No pin marked VS ON.

The only voltages that I am reading on any of the pins (with the exception of the AC in) are:

Pin marked 5V-1 = 5 volts
Pin marked AC Detect = 3.2 volts