VESTEL 17IPS61-3 shorted output diodes

[John843883]

Hi everyone!

I've got a 22 inch Toshiba TV which is really just a rebaged Vestel and like so many of these things the PSU has got a shorted diode on the 12v rail preventing it from working.

Now replacing the diode is simple enough but having read this thread https://www.badcaps.net/forum/showthread.php?t=42137 I'm leaning towards fitting a high voltage fast recovery diode instead but my concern is how hot would such a diode get with the increased voltage drop? Should I parallel multiple diodes up like Vestel did?

The back of the TV reveals a power draw of 50w max which is just over 4.1 amps @ 12v.

The PSU is a VESTEL 17IPS61-3 and can only accept DO-201 diodes but I can't find any suitable 300v+ 5 amp schottkys in that package which is why I'm considering a regular fast recovery diode instead.

The 24v rail currently has a single 200v UF5402 installed which I plan to upgrade to the 400v UF5404 in order to cater for the increased reflected voltage spike which the 12v rails underrated schottky used to clamp.

If anyone has repaired one of this PSU's before I would be interested in knowing what replacement part you fitted and how long the repair has lasted, I know these boards are infamous for being junk but I'm trying to avoid a repeat diode failure in future from selecting an under rated part.

Thanks!

[John843883]

Re: Vestel shorted output diodes

Update: Well I got no replies so I went ahead and installed 3x STTH5L06 for the 12v rail in place of the 2x SB5100 and 1x SR5010 trio whilst for the 24 rail I installed a UF5404 instead of the UF5402.

The SR5010 is the one that originally failed.

In hindsight I probably could have gotten away with just installing one or two STTH5L06 but I chickened out just in case they get too hot once the TV goes back to its owner, I made sure to bunch them all together to help with thermal balancing issues.

The TV now works and is now being tested for a few hours.

[vinceroger69]

Re: Vestel shorted output diodes

Thanks for the update and the list of replacement parts you used, and im glad you managed to fix the tv for the owner.

[John843883]

Re: Vestel shorted output diodes

Thanks for the update and the list of replacement parts you used, and im glad you managed to fix the tv for the owner.

Thanks. I just can't believe they didn't use diodes rated for the task.

Granted I couldn't find any appropriately rated Schottkys in the required DO-201 package but Vestel could of at least made PCB provisions for a TO-220 part, I found loads of them online that would have done the job. But that would require heatsinking and Vestal don't want to spend that extra dollar.

[stj]

Re: Vestel shorted output diodes

i would replace parallel diodes with a single one in a to220 package.

example, some ryobi chargers use a parallel pair of MBR5200 (5A 200v)
i replace them with an mbr40250 (40A 250v)

that wont fail again!!!

[John843883]

Re: Vestel shorted output diodes

i would replace parallel diodes with a single one in a to220 package.

example, some ryobi chargers use a parallel pair of MBR5200 (5A 200v)
i replace them with an mbr40250 (40A 250v)

that wont fail again!!!

Nice find!

Hmm well I just tested by spreading the legs of a TO-220 device and compared it to the shorted diode and it could certainly fit into the DO-201 holes at a push, but I don't think it would last in this application as the voltage spikes across the diode when the TV is first turned on reach nearly 300V!


And would you believe it I just came across this cute little DO-201 heatsink in my parts box after I had already screwed the TV back together.

[stj]

Re: Vestel shorted output diodes

where are the spikes originating? is the opto-isolator not reacting fast enough?

[John843883]

Re: Vestel shorted output diodes

where are the spikes originating? is the opto-isolator not reacting fast enough?

Goodness knows but it appears to be the most common cause of failure in these models. This thread has some waveforms showing the extent of the spikes https://www.badcaps.net/forum/showthread.php?t=42137

[stj]

Re: Vestel shorted output diodes

btw, you probably dont need a heatsink - the original diodes didnt,
and if you mount it vertical or upside-down it already has a copper plate.

[vinceroger69]

Re: Vestel shorted output diodes

Goodness knows but it appears to be the most common cause of failure in these models. This thread has some waveforms showing the extent of the spikes https://www.badcaps.net/forum/showthread.php?t=42137

yes i remember toms post regarding this issue im sure your replacements will last a lot longer.

[stj]

Re: Vestel shorted output diodes

it's a very short spike, i wonder if a parallel snubber cap+resistor would squash it?

i have seen that done across schotky rectifiers in lite-on built monitors.

[John843883]

Re: Vestel shorted output diodes

btw, you probably dont need a heatsink - the original diodes didnt,
and if you mount it vertical or upside-down it already has a copper plate.

Yeah I guess I went overkill with the diodes, just trying to make sure they don't fail again at some point down the line (the TV is used in a holiday home 200+ miles away). I don't do this as a full time thing though so sparing an extra component here and there isn't too big of a deal. Maybe the extra junction capacitance will reduce the peak voltage lol.

yes i remember toms post regarding this issue im sure your replacements will last a lot longer.

With a bit of luck If it wasn't for that thread I would have just fitted some exact replacements and assumed current hogging was the cause.

[ReeceyBurger123]

Re: Vestel shorted output diodes

You can use a 10amp 200v rated TO220 with a small heatsink thermally glued to it. It will last longer than the Tv will fact. Also if its a 17MB95 I suggest you factory reset it after fixing the diodes as they are shite boards anyway. Heres a IPS that I did the diode mod too also done it to others:

[ReeceyBurger123]

Re: Vestel shorted output diodes

The reason for failure is because of the way Vestel run the supplies I wont go into much detail but the diodes are over voltaed at start up, I also read that the way Vestel bend the legs of the diodes can lead to failure as the legs stress the diode but Im unsure if thats the real cause.

[John843883]

Re: Vestel shorted output diodes

You can use a 10amp 200v rated TO220 with a small heatsink thermally glued to it.:

That's a neat way of doing it! But unfortunately I don't have any thermal glue to hand.

Also if its a 17MB95 I suggest you factory reset it after fixing the diodes as they are shite boards anyway. :

Dam I forgot to check, when sort of things usually go wrong? Also are the power LED's supposed to flash a few times during power on? I figure its just the board booting but don't have anything to compare it to.

This model is branded as a Toshiba 22d1333b so maybe its a custom thing they have going.

[ReeceyBurger123]

Re: Vestel shorted output diodes

Thermal silicon is cheap off ebay, about £1.50 for a 10 gram tube and it works well tbh. Also theres alot of issues with the software corrupting causing the standby Led just to flash, its normal for it to flash at startup though. Luckily for you if the firmware does go I have a thread which has the firmware for that exact Tv for free so your fine

[stj]

Re: Vestel shorted output diodes

10g??
you got robbed!
http://www.ebay.co.uk/itm/131516987160

[ReeceyBurger123]

Re: Vestel shorted output diodes

10g??
you got robbed!
http://www.ebay.co.uk/itm/131516987160

Lol thats probably just melted plastic in that though

[John843883]

Re: Vestel shorted output diodes

Thermal silicon is cheap off ebay, about £1.50 for a 10 gram tube and it works well tbh.

Is this stuff suitable for future repairs? http://www.ebay.co.uk/itm/Halnziye-H...-/262588989842

Also theres alot of issues with the software corrupting causing the standby Led just to flash, its normal for it to flash at startup though.

Phew, that's a relief. I was thinking maybe the voltage spike which killed one of the original diodes had also taken out something on the logic board so perhaps the flashing was some kind of error code.

Luckily for you if the firmware does go I have a thread which has the firmware for that exact Tv for free so your fine

Thanks fam, its great that we have people like you out there uploading this sort of thing for the repair community.

[ReeceyBurger123]

Re: Vestel shorted output diodes

yes i remember toms post regarding this issue im sure your replacements will last a lot longer.

Vince you remember the mod I did on that IPS11 with the output diodes thats working great as well ?