compaq mp2810 fuse/viper/PC817 blows - diyAudio
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Old 22nd March 2012, 04:31 PM   #1
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Join Date: Mar 2012
Default compaq mp2810 fuse/viper/PC817 blows

i replaced
SFH617A with PC817 ,
viper100A with viper100A,
capacitor 53uF 63V with 100uF 63V

default main fuse is T2.5A, i try 2A and it blow.

T2.5A will not burn out, but viper explodes!!

without viper pcb nothing is occurs

projector has been tested without lamp.

projector image
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viper pcb
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bottom pcb
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Old 23rd April 2012, 10:45 AM   #2
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It still sounds like a short circuit. Have you checked the voltage coming into the board?
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Old 26th April 2012, 01:25 AM   #3
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Join Date: Mar 2012
i change everything on viper pcb(capacitors, resistors, diodes), but now i dont have the courage to turn on

voltage from main power supply board is -325VDC ?


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i find on this forum similar topics, also problem with "viper explode"

Infocus lp350 power supply issue
Help repairing Infocus LP530
Help with InFocus LP340

Quote:
the ultimatum is the MOSFET inside the Viper100 shorts. this is because the 100UF cap that sits next to it, dries up. this causes noise on the VCC supply pin that powers the logic circuits that reside internal to the Viper100A. This causes spikes on the gate of the MOSFET internal to the Viper100A, causing mass-self-destruction of the entire power supply.

The spikes will make it through the transformer onto the secondary side. This sometimes causes the 12V secondary rectifier diode to short. When this happens, the filter capacitors becomes a reactance to AC voltage, of near 0 ohms. this causes a current overload, blowing the MOSFET internal to the viper100A, thus blowing the entire viper100A apart. sending hundreds of volts down the logical circuits inside the Viper100A, blowing up the Viper100A's VCC supply regulator. this also blows the opto-isolator that regulates the main supply.

Then the main supply shuts down, and is dead forever to come until repaired.

Another thing that happens is sometimes when the lamps wear out, the power factor corrector circuit that boosts your voltage up to 400V, the inductor starts to short, develops shorted turns, overheats, etc... this will cause instant destruction of the associated MOSFET and the L6561D driver circuitry. sometimes it will blow the zener diode out with it, it sits inside an SO-23 package.

the diode mod i do, is a 2 amp 800V diode that goes in between the viper100A VCC supply pin, and the supply regulator on the power supply board. When the MOSFET inside the Viper100A shorts again, this blocking diode will block the reverse flow of 400V into the power supply, protecting it from mass destruction. Then only simply changing the output diode and Viper100A would restore the power supply into full operation once again.

Another thing that can be done is adding a fuse in the B+ boost supply to the Viper100A regulator. use an amperage that is same or near the maximum current rating of the MOSFET of the viper. if MOSFET shorts, it will pop the fuse without blowing the viper to bits and everything else with it.

Viper100A is rated for MAX 100watt power supply. 100watts at 400V is 4amps max current draw from viper100a before its ratings are exceeded.

but im not sure is this applies to my issue ?


can i try to remove viper100a , and then to turn on projector for measure voltage ?
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Old 14th May 2012, 02:54 PM   #4
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the transistors that feed the viper's logic B+ are shorted.
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