Epson EB-U42 projector / Caps with 0.7 ohms ?!

[narf]

just a short update: i soldered in the new buck converter IC (TI TPS54335) and have no shorts anymore. but my initial problem stays the same: the initial mosfet on the mainboard has no gate voltage and doesn't forward the 12V. i even exchanged that chip, but no luck there.

i found that the white cable of the connector ("main_on") has 0V, too. i think, this one could supply the gate voltage. does this come from a faulty PSU or is the error somewhere on the mainboard? is there a "typical" culprit?

[Diah]

just a short update: i soldered in the new buck converter IC (TI TPS54335) and have no shorts anymore. but my initial problem stays the same: the initial mosfet on the mainboard has no gate voltage and doesn't forward the 12V. i even exchanged that chip, but no luck there.

i found that the white cable of the connector ("main_on") has 0V, too. i think, this one could supply the gate voltage. does this come from a faulty PSU or is the error somewhere on the mainboard? is there a "typical" culprit?

main_on are reverse pulse at time MB send this pules to PSU i did explained this at post #5

[nossebrofredrik]

Hi,
I found this thread looking for a service manual for a EB-U42.

I have had the same problem with the IC3000 being shorted, I have replaced it but in the process some supporting components flew away.

Needed alot of heat to get the old chip off. So if someone knows the values of R3015, C3008, C3006 and R3011 it would be greatly appreciated.

Attached is a close-up photo of the placement

Thank you.


Attached

[Goldeneyes]

Hi,
R3011= 2.7 k ohm (tested on board)
R3015= 10 k ohm (tested on board)
About c3008 and c3006 you can use the same dimensions as close as possible I dont have lcr meter to measure.
attached picture may help to check the pins too.
goodluck

[nossebrofredrik]

Thank you, I shall test it and see if it works.

[Goldeneyes]

You welcome, hope it works.
also 12 volts in standby mode is correct and normal, after power on it will change to 17 volts

[nossebrofredrik]

I have done some reading of the datasheet of the TPS54335-2. C3006, R3011 and C3008 seems to be the gain of the error amplifier. R3015 is in a voltage divider with R3012 and R3013 to set the output voltage.
If R3015 is 10k and I measured R3012 and R3013 to 2.1k and 9.1k on the board, the output voltage would be around 1.7V. Anyone know if this is correct? The internal reference voltage is 0.8V.
I have made a schematic in KiCad where I put in the values I have measured and those I have been told. For C3006 and C3008 I took the example values from the datasheet.
I have attached the PDF of the schematic if anyone would like to see or have any input on it.