2275 Power Supply Troubleshooting

[Cryptical11]

I just now have also found a smoked R801 resistor on my 2275 PS board. The resistance measures over limit (OL) and it is burned. What related issue may have caused this resistor to burn? Is this R801 resistor intended to fail in order to protect other components? I was planning to replace it with the same 1/4 Watt resistor specified on the schematic. I have marked up the schematic with values I have tested so far in red.

 

[sanjib]

Check H801 and H802, in particular, H801

 

[Cryptical11]

Check H801 and H802, in particular, H801

I just tested H801, H802 and H803 with my multimeter. They test good. The updated test values for the power supply board are attached. I am not sure what else to test on this power supply circuit board. What do y'all think?

 

[mbz]

Replace R801 0.25W and power up on DBT. Thinking H801 is almost toast, regardless of testing ok. Check emitter to GND
and collector to GND voltages on DBT.

 

[sanjib]

At this point, I would suggest replacing H808, H811 with MUR 1620CT, H801 with MJE15032G, all of the electrolytic caps. After that as mbz suggested power on the unit with DBT. If the problem persists (that is unlikely) you may have to change the other semiconductors on this board.