On Mon, 6 Oct 2008 06:56:38 -0700 (PDT), EADGBE
put finger to keyboard and composed:
Richard:
Per your request, I have taken a photo of the back of the circuit
board.
http://i240.photobucket.com/albums/f.../CIRCUIT_3.jpg
I have numbered all of the connections so that no one will get
"lost".
They are as follows:
1 - speed control pot connections
2 - 43k resistor
3 - 332 ohm(?) resistor (orange/orange/red?/black/brown)
4 - 421M ohm(?) resistor (yellow/red/orange?/blue/green?)
5 - inductor (olive "resistor" shaped part)
6a - negative lead of 10uF/25v electrolytic
6b - positive lead of 10uF/25v electrolytic
7a - negative lead of 3.3uF/25v electrolytic
7b - positive lead of 3.3uF/25v electrolytic
8 - pink "resistor" (red/red/brown/grey/black)
9 - 22 ohm green resistor (red/red/black/silver)
10a - cathode of black diode (yellow stripe is closest to this
connection)
10b - anode of black diode
The positive and negative power connections are also indicated.
SOME QUICK ADDITIONAL COMMENTS, based on comments I have received so
far....
REMINDER: I know that I could easily get another motor. I AM SIMPLY
TINKERING FOR THE SAKE OF TINKERING, and it's a good opportunity to
learn a bit about this circuit. That's all!
Someone said that they found a substitute for AN6610, but that is NOT
the part number.
Sorry, my mistake.
The burned part says "AN6601". It is made by
Matsu****a (Panasonic). I do indeed have an exact replacement for
this part in hand. I found it online at a supplier specializing in
obsolete semiconductors.
I have tested the motor by running 9 volts directly into it. The
motor runs smoothly and quietly. I will take a current reading, just
to see what I find. But the motor appears to be OK.
I am currently going on the assumption that AN6601 failed on its own
and/or because of the fault of the diode.
This is how I see your circuit:
+ o--------|-----|-----|---------|
12V | | | ___|___
| | | | |
| | | R4 R2 43K
+_|_ | | |_____|
C6 ___ | | | D10
10uF | | | |-------||--- L5 --|-----|
25V | | | | | |
| R8 Motor R3 3K3 +_|_ |
| 220R| | | C7 ___ |
| | | |- VR1 5K 3.3uF | |
| | | |----| 25V | |
| |_____|_________|___________________| |
| | |
| | voltage |
| | feedback |
| AN6601 --------------------------------|
| |
0V 22uH | |
- o-- L9 --|-----------|
AFAICT, the AN6601 IC senses the motor voltage via the potential
divider consisting of VR1, R2, R3, and R4. I suspect that if this
voltage begins to increase, then D10 conducts, causing the voltage at
the AN6601's control pin to rise with respect to its supply pin, thus
turning off the AN6601 and reducing the motor current.
- Franc Zabkar
--
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