820-3478-A no power

tlough75

Member
I got a dead 820-3478-A on the bench. Tried new PSU but none of the LEDS light up. Anyone fix any of these here?
 

2informaticos

Administrator
Staff member
Please, post usefull information!
We need some readings, like voltages, diode mode to ground...

Start with U/Q8470.
 

tlough75

Member
Ok, U8470:

1: 12.15V
2: 3.42V
3: N/C
4: GND (0)
5: 3.851V
6: 21.61V
7: 12.15V
8: 12.15V

In the schematic it shows Q8470 as having 8 pins but on the board I see 4. They all measured 12.15V
 

2informaticos

Administrator
Staff member
1V should be more than enough in such.
But you will need a bench power supply which can support at least 10A, better 20A.
 

tlough75

Member
Yeah unfortunately mine can only do 3A. I'm going to buy another one soon. When I inject 1V @ 3A the only thing that gets warm is the PCH....U1100
 

2informaticos

Administrator
Staff member
If U1100 heats with 1V, no more doubts.
Always let amps at max, you can't adjust the current.
Current sinked by the board is accordingly with injected voltage and internal resistance of the short to ground...
 
Last edited:

tlough75

Member
gotcha, yeah I am not limiting the current, my PSU has the option to turn off over current protection and overvoltage protection. I took it back to customer and told them to replace the board. It would have been nice if my PSU could go up to 10A, I would have loved to see the PCH get red hot!
 
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