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miatawnt2b 22nd February 2005 08:28 PM

Help with InFocus LP340
I'm sure this isn't the right forum, but I need some help with an InFocus LP340. Seems the power supply cooked (it's an ASTEC AA21620) and a few parts exploded on the board. I am looking for a schematic for this unit. Ideas?

sjetski71 23rd February 2005 12:08 PM

You may have tried it already but googling for " AA21620 " yields about 16 results. Maybe the answer is there somewhere?

Good luck either way as sometimes this kind of info is jealously guarded by service techs.

btw, have the Infocus LP335 here. Works a lot better than i thought it would and the deal was too sweet to pass up (free extra bulbs and everything!).

JCoffey 23rd February 2005 02:30 PM

Search on Ebay for the LP340. I have the boxlight version myself. You can find parts units pretty often for them that you could possibly just swap out the board with.

BTW, would you happen to be the same guy that IM's me over at AVS forums about a blown part on the PS board? I just got it a couple days ago. I'm planning on pulling mine apart this weekend to look at the part if it was you.....

miatawnt2b 23rd February 2005 03:57 PM

nope, not the same guy. I am looking for part numbers for U1, U2 for the ASTEC AA21620 supply in the LP340.

TaskMaster 23rd February 2005 06:32 PM


Originally posted by miatawnt2b
I am looking for part numbers for U1, U2 for the ASTEC AA21620 supply in the LP340.

This guy here claims U2 is an STMicro Viper100A.

1pancrazio 1st December 2005 12:00 PM

my problem is infocus lp340power supply faulty?
help for schematic diagram. antony tank you

mbates14 27th March 2007 03:41 AM

i know this is an old thread. but hte power supplies fail in several way.s you can send them to me to get fixed, i will fix them for you.

the viper will fail, and will take out the opto isolator, the SMD regulator transistor, a startup resistor, the viper itself, 3 IN4148 SMD diodes, 100uf 25v capacitor, and a diode in the secondary of the power supply. this is all caused by the regulator opto failing, running the viper past its specs.

good luck getting that silicone **** off the viper heatsink to remove it. fun fun.

also there is a 0.1uf 400v starting capacitor that goes bad and will blow the main MOSFET and a series of chips and other parts. this is due to starting the wrong lamp type in the wrong power supply. thats why infocus issued a Rev01 update.

also another known common problem is it will light the lamp, but the lamp will be very dim, and then it cuts out. and retries.

this is caused by shorted windings in the boost B+ converter. that somtimes will fail, not very common, but does occure.

the most common failures is the starting capacitors/resistors, and the opto-isolator failure taking out the viper, and a series of other components. all of which i can fix.

CliffS 4th April 2007 05:48 AM

infocus lp350 Power Supply
I have a lp350 that will not power up. I have replaced the Viper, the 100uf cap and a surface mount transisistor that were obviously damaged but it still wont power up and the drain pin on the viper is not oscillating. I can locate the optos but not the diodes you refer to, however I have found some sm diodes in 2 packs that seem to have one blown. I dont have any clue however the original orientation of these diodes. Im about stuck, any clues, schematics or would you like to fix it?

lp350fool 30th June 2007 03:26 PM


Have you fixed your LP350 PS?
Sine yesterday I have the same problem, the PS just exploded.


CliffS 1st July 2007 03:12 AM

LP350 Power Supply
No I am still pretty well stuck with out the schematic. The viper is easy enough to spot and is available through digikey as are the caps that are probably blown as well but the smt diodes in 2 packs are pretty hard to figure out. Hopefully someone will come one here and clear this up for us

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