BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

[Marsie]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Hi.

Got av in. Sound out the speakers.
The signals PWM_DIM and BKL_ON/OFF.

Measured at the LED driver board:

25V and 0V.
PWM_DIM on oscilosscope gives a pwm, about 55Hz, 3Volt peak-peak (0V-3V).
BLK_ON/OFF 3Volt DC

Disconnected BLK_ON/OFF and put point on LED-driver board on OV. Still no light.

Should PWM_DIM be 5V-p-p and not 3V-p-p?
And/Or BLK_ON/OFF 5V?

[Astra]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Sorry if this is the wrong place to post a thank you in but by following the helpful pointers given in this thread, I have managed to repair a faulty Sharp LC-24LE240E TV. This set has a Vestel 17PW80 v3 PSU. D708 (SB5100) had gone short circuit. I have replaced all three with new ones from the same bandolier and thermally bonded them. I also bonded the two UF5402 Diodes while I was at it. Set now working fine.
So Thank You All.

[kidneystone]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

I have the 17PW80 V2 power board in my Bush TV. follow all the advice on here and found that D709 is faulty. I removed the diode then quickly powered up the TV and it worked, thanks for the advice. I am going to remove D709 and D710 and replace all three. My question is, on the diode I have removed the writing says SB5B0 but when I look round on ebay etc I keep finding SB5100, are these the same?

[flocko]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

yes both are schottky diodes and the SB5100 will be fine

[kidneystone]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

yes both are schottky diodes and the SB5100 will be fine

Thank you for the advice. I will order some now and let you know if I am successful.

[kidneystone]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

I changed diodes D708, D709 and D710 after reading through this thread and now I have a fully working TV again. Thank you to everyone who contributed to this thread.

[gasman77]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Remove each of D708, D709, D710 and test out of circuit for shorts. You can briefly run the set with whichever diodes are still good. (One or two, max one minute running time.) CRAPPY VESTEL parallel three diodes. If one diode gets slightly hotter than the other two, it ends up taking more current than the others, causing it to heat up more, causing it to take more current.... I'm sure you can see this cycle will eventually lead to a diode failing. Built to fail!

Hi Tom, couldn't believe it when I read this ! Paralleling diodes, what a joke, why not a single schottky thats up to the job? as is now in the set I just fixed. I used a single 12Amp 600v simply because I had one and all ok, no need to mess with trying to thermally bond individual diodes. Its my guess that was a novice designer under the mistaken belief that putting them in parallel reduces the forward voltage, no it doen't the VF we be that of the lowest in the group which will then take the brunt of the load leading to failure and starting the chain reaction on the remainder.

[coojoe_213]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Hi everyone. I have Techwood tv 22 inch with Power Supply 17pw80 V2.
The tv, doesn't work. I check all diodes, they are fine. Can you tell me, what to do...:/
When i turn on the tv, the transformer have sound ''buzzzzz' or ''humming'..., why?

[Gamma30]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Remove each of D708, D709, D710 and test out of circuit for shorts. You can briefly run the set with whichever diodes are still good. (One or two, max one minute running time.) CRAPPY VESTEL parallel three diodes. If one diode gets slightly hotter than the other two, it ends up taking more current than the others, causing it to heat up more, causing it to take more current.... I'm sure you can see this cycle will eventually lead to a diode failing. Built to fail!

Hi Tom - thanks very much for the info. Found a faulty diode exactly as you said and will replace all 3 next time I visit the home of the black screen Bush TV.

[michael dranfield]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

As support for the UF5404 option was mixed, and a 'quite advanced' option might be over ambitious for a first repair, I decided to play it safe initially and replace the bad D709, plus its paralleled D708 and D710, with a new set of three UF5402's.

I reassembled my Sharp 24" TV last night, and can happily report that it powered up normally and worked perfectly for the hour or so that I had it on.

So thank you BadCaps, and everyone that contributed to this thread!

If I was you I would fit the correct diodes, D709, D708 D710 type number SB5100 are Shotkey diodes and have a much lower forward voltage drop, you should not be fitting UF5404 diodes in this position as it will cause your output voltages to be wrong, take no notice of what part number it shows on the circuit diagram , this is printed wrong.

[gabiz_ro]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Forward current 3A vs 5A
Forward voltage 1V vs 0.85V
It should work fine,with UF5402

[ReeceyBurger123]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

I use 5402 in place of them more reliable.

[michael dranfield]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Forward current 3A vs 5A
Forward voltage 1V vs 0.85V
It should work fine,with UF5402

SR5100 Forward voltage drop as measured on my Peak atlas DCA55 which was re calibrated 4 weeks ago.

[gabiz_ro]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Comparation was with data from datasheets.
It may be at Imax,don't remember now.

[tom66]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

SR5100 Forward voltage drop as measured on my Peak atlas DCA55 which was re calibrated 4 weeks ago.

At the low current the DCA55 uses most diodes will test with quite low forward voltages, as gabiz says the diode may be rated at full forward current.

[drseeall]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

I've got a Bush 24127FHDDVD that has hardly been used with no power light. It has one of the Vestel 17IPS61-3 variant PSUs.

All caps look OK. It seems it has the common diode failure fault.

D9 - UF5402 (?) - seems OK (0.752v/0.435v)

D25 - SR5010 - SC

D12 - SR5010 - SC

D11 - empty slot

D10 - SB5100 - SC

What are the best diodes to use to replace the faulty ones (as an upgrade to prevent the same failure in future)?
Can I use the same type for all three even though the originals use two different specifications?

Alternatively, can I put an extra one in the vacant position D11 (in parallel) to "beef" it up a bit?

I understand I also need to glue them together with thermal epoxy.

TIA
DrSeeAll

[drseeall]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

After a bit more investigation just one of the SR5010 was shorted. It was because originally I was testing the parallel components in situe that all three appeared defective.

It seems SR5010 and SB5100 are equivalent and rated at 5A 100v.

To upgrade the system I intend to replace all four diodes with UF5408 (rated at 3A 1000v) and add an extra one at D11.

Can someone please confirm that this should be OK regarding the forward voltage etc

TIA
DrSeeAll

[drseeall]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Well after receiving no confirmation, I went ahead and replaced all six diodes with UF5408 and thermally bonded the adjacent ones together.

I can confirm the TV is now working again (after 90 minutes bench-testing) and hopefully will be proofed against the same failure again.

Thanks to all participants in this thread.

[gazztheman]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

Woke up this morning and found our little bedroom BUSH TV dead.
After investigating I figured the PSU was dead.
I Googled 17PW80 to see what, if anything, was known and found this forum.
After reading the many and various entries I now have 10x UF5404 diodes on order from Farnell and a tube of Halnziye thermal adhesive glue on order from ebay.
Great!

[boghopper]

Re: BUSH LED2497ODVDFHD, 17PW80 V2, Dead!

hi, i have replaced D708 D709 D710 after finding that my JVC 24" tv wouldn`t turn on this morning, i replaced them with sb5100 diodes, but this hasn`t worked, all the caps are in good condition (not domed or topped out). i have no way of testing individual components, only by sight. so is it worth me changing the two diodes next door to the 3 i have changed today?

any advice would be much appreciated, i don`t want to send this for recycling if it`s an easy fix.

many thanks
Glenn