?ann fim., 25. n¨®v. 2021 kl. 15:15 skrifa?i k6whp <k6whp@...>:
On Thu, Nov 25, 2021 at 01:06 AM, Albert Otten wrote:
Thanks. Saw the eBay listing. My motor and fan work fine. Was looking for
explanation/documentation of the whole board and why such a seemingly
simple concept of a cooling fan had all the added circuitry.
While I¡¯ve never seen a 7704A, my guess would be that the circuitry is the
same as in the 485, 2465 and other scopes that use the Siemens motor. The
circuitry does two things; commutates the brushless motor on signals from
the Hall effect sensors in the motor, and temperature-regulates the fan
speed.
The impeller fan design in the 2465 is IMHO vastly better than the PC fan
used in my 2467. The former is virtually silent, while the latter is
annoyingly loud and whiny. I imagine by that time, it would have made for a
fair cost saving to design in a by-then commodity PC fan, which is
presumably why Tek went backwards in this respect.
