Transformer substitution - Sanyo DP42849-01

[lookimback]

Over the past couple of months I've encountered 5 of these inverter boards (P/Ns 1AV4U20C41500 and 1AV4U20C41501) which had failed. Of those 5, 2 were PWM failures and 3 were inverter transformer failures. I have failed 3 separate times at disassembling the transformers for rebuild. My most recent failure involved soaking the transformer in MEK overnight to dissolve the varnish which holds the ferrites in. The varnish dissolved (including on the primary windings which weren't bad) but the ferrites still cracked. Even when I have managed to get the ferrites out in one piece, the bobbin that the secondary is wound on usually breaks because it is fused to the primary bobbin.

So, I've essentially abandoned the idea of rebuilding them. Now my idea is to locate a suitable SMD substitute and and make an adapter board. The adapter board would have the pin configuration of the original transformer and go in it's place. Then a SMD transformer would mount on that board and have tracings go to the correct pin locations. I at least think this could be done.

My question though, is what I need to take into consideration when looking for a suitable transformer?

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Here's what I know about the transformer.

Primary Winding 115 turns

Secondary Winding 550 turns

Primary Resistance 0.7-0.8 ohms

Secondary Resistance 26-27 ohms

How can I figure out the frequency?

And the type?

[stj]

Re: Transformer substitution - Sanyo DP42849-01

the datasheet for the driver chip will give you the frequency and sometimes an aplication circuit with transformer details.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Data sheet for the PWM just says 30khz to 500 kHz.

The PWM is a switch mode power supply controller so I guess that means I need an smps transformer?

[stj]

Re: Transformer substitution - Sanyo DP42849-01

are you sure that drives the lamps?
that board looks like a combined psu and invertor.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

It is a combined PSU and inverter. I'll look at the data sheets from the other ICs and see if any might be the lamp driver.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Maybe it's this one?

[stj]

Re: Transformer substitution - Sanyo DP42849-01

no, that's the pfc circuit.

trace the transformers back to the fets that switch them.
then trace the gate pin from those fets to find the drive chip.

does it have parts on the other side of the board?

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Here's a pic of the bottom and a link to one of my older threads which has some good closeups of the bottom.

https://www.badcaps.net/forum/showthread.php?t=33261

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Are these the FETs?

Edit: Only other ICs on the board are op-amps and standby controller.

[stj]

Re: Transformer substitution - Sanyo DP42849-01

controller

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

OK, that was the one I originally thought. The data sheet is in post #4. But it only says 30khz to 500khz. So I guess I'll need someone with an oscilloscope right?

[stj]

Re: Transformer substitution - Sanyo DP42849-01

frequency counter i think you mean.

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

So one of these would work then?

http://www.ebay.com/itm/OSCILLOSCOPE...item19eae5e6d7

http://www.ebay.com/itm/Frequency-Co...item1e8cf01fd0

[stj]

Re: Transformer substitution - Sanyo DP42849-01

before you spend much money,

there are nice projects.
make one.
https://duckduckgo.com/?q=atmel+70mh...-wt&kp=-1&kv=1

another option, the datasheet implies that the frequency is directly related to the voltage on one of the pins.
so maybe meter the voltage to calculate the frequency.

finally - check for cheap clone transformers.
like here - this seller has a bunch.
http://stores.ebay.com/lcd-led-parts

[stj]

Re: Transformer substitution - Sanyo DP42849-01

http://danyk.cz/avr_fmetr_en.html

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

Sweet! So we have the circuits resonant frequency. Or, will have once I build the counter. Now I guess all that's left to determine is the transformer's input voltage and current. I get nothing with my volt meter because the frequency is too high.

[tom66]

Re: Transformer substitution - Sanyo DP42849-01

I wouldn't stick that frequency meter within 2 foot of any high voltage or mains potentials.

[budm]

Re: Transformer substitution - Sanyo DP42849-01

You will need to know the inductance, the DCR of Primary and Secondary, the turn ratio, the power requirement, etc.
http://www.coilcraft.com/ccfl.cfm

[lookimback]

Re: Transformer substitution - Sanyo DP42849-01

So that counter would probably fry?

Post #2 has turns of primary and secondary. Turn ratio would be 1:4.78

DCR? If that's resistance, it's also in post #2.

How do I determine inductance?