estudio 35 fan noise

[umdatchau]

The developer fan (located near the back of the machine in the center. It appears that it cools the developer unit) will run normally during copying/printing but goes into a pulsating mode a few seconds after copying is done. Fan speed goes up and down in about 3-5 second intervals, never ending. I changed the fan, the engine board and power supply with no effect. I think that leaves the main board with all of its settings, something I would dread doing. Any ideas? Thx john

[blackcat4866]

Are there any other symptoms? If it's just the sound generated by the fan speed, I might try to explain it away. After all this machine is 12 years old. That's probably not the only sound it's making.

I would be curious to know if the DC voltage to the fan is fluctuating in the same cycle as the speed. If yes, I would take it a step further: I would monitor the 24vdc to frame ground. If the 24vdc is fluctuating, it may be a PS issue. Then I would monitor the grounding signal to frame ground. If it's the ground signal that's fluctuation, then it is the Logic Board. That's actually the easiest board on the machine to replace. Just transfer the EEPROM from the old board to the new board, plug in all the connectors, and you're all done.

=^..^=

[umdatchau]

Are there any other symptoms? If it's just the sound generated by the fan speed, I might try to explain it away. After all this machine is 12 years old. That's probably not the only sound it's making.

I would be curious to know if the DC voltage to the fan is fluctuating in the same cycle as the speed. If yes, I would take it a step further: I would monitor the 24vdc to frame ground. If the 24vdc is fluctuating, it may be a PS issue. Then I would monitor the grounding signal to frame ground. If it's the ground signal that's fluctuation, then it is the Logic Board. That's actually the easiest board on the machine to replace. Just transfer the EEPROM from the old board to the new board, plug in all the connectors, and you're all done.

=^..^=

No other symptoms. In fact, the machine is still making great copies. I have already replaced the fan, power supply and logic board to no effect. The parts I used were out of another working 35 but it may have had same problem and I just didn't notice it. What I was worried about was the system board. From what you said, that is not a problem. Thx blackcat.