EADGBE wrote:
I have a "rainy afternoon project" that has got me puzzled.
I have an old Pioneer cassette deck that I am restoring.
The capstan motor worked for a short while, then it stopped.
The casing of the motor felt VERY warm, so I knew something was
amiss.
(One of the voltage regulators in the deck's main power supply became
EXTREMELY hot whenever the capstan motor was connected, which was
another clue).
Suspecting a short in the capstan motor, I took the motor apart.
Take a look at what I found when I examined the motor's internal
voltage regulator circuit board...
http://i240.photobucket.com/albums/f...3/SCORCHED.jpg
The motor's voltage regulator had burned itself up. Look at how
scorched the circuit board is!
I have a replacement regulator, but I want to make sure that all is
well inside this circuit before installing the replacement. (Yes, I
KNOW that I could simply get another motor, but remember, I am
tinkering for the sake of tinkering!)
So I have been checking all of the other components in this circuit,
to verify their health.
The one component that has me puzzled is the small black "diode"
indicated at the bottom of the photo.
There is no mark on this component other than the yellow stripe you
see.
I cannot get any type of reading on this component when I use my
multimeter -- I get nothing using my diode check function (forward or
reverse bias), no continuity, no resistance reading. It must be
faulty, I am assuming.
Then you're somewhat stuffed without a schematic I'm afraid. Unless you
can reverse engineer the circuit ! I've just been through a similar
problem myself where the parts list had everything on it except RESISTOR
values ! what IDIOT was responsible for that I hate to think.
For any AUDIO people listening, that company was MIDAS btw. I've been in
contact with them for about 2 weeks now about it and all they did was to
re-send the same list in a different file size with the resistor values
STILL missing.
The other component that has me puzzled is the olive green "resistor"
just above the larger blue electrolytic capacitor. I get a steady
resistance reading of .5 ohms on this component.
Plausible. Low value Rs aren't always marked conventionally. Most likely a
current sense R.
Graham