"jakdedert" wrote in message
...
wrote:
snip
Thanks Arfa. I shall try those things now.

Unfortunately there are no fuses in this unit. However, upon a visual
inspection I identified a transistor with visible damage to its
ceramic exterior. This transistor, a C1815, is in place but almost
half of its ceramic exterior has been chipped off. Quite a bit of
copper is showing, but there is no broken connection.

Does anyone know whether it's likely that this sort of damage would
stop a transistor from working? I have taken a digital image:

http://xs.to/xs.php?h=xs217&d=07281&f=transistor.jpg

(the chipped transistor is circled in red).
Thanks


Was that a shill just to get to the 'two free ipod nanos'? In any case, I
didn't wait for the pic to load. I hate popups, but I hate audio popups
even more.

However, when I see a component damaged as you describe, I consider it
toast and start looking for the cause. It's not the external damage
that's the issue. That transistor has literally exploded through some
fault; either an internal fault in the component itself--or more likely--a
fault in the circuit, which overloaded it.

jak


Agreed. However, it looks like that transistor is in the bias oscillator,
rather than the power supply. If it's gone short circuit though, it may well
have loaded up the power supply, and done some damage. As far as there being
no fuses in there, I bet there are somewhere - but they might well be
fusible resistors, and if you don't know what you are looking for, you might
struggle to spot them. If the silk screening on the board has circuit
symbols at each component location ie a little zig-zag for a resistor, look
to see if you can spot any zig-zags that have an extra little 'sine wave' at
the end of them, indicating that they are a fuse type. You can usually spot
them because they look 'different' from all the normal resistors. They are
often, although not always, stood on end, and usually have matt finish
bodies, often brown or grey. You will often see two gold bands on them also.
The circuit descriptor may be different from other resistors. Sometimes,
manufacturers will use, for instance, "PR" for "protector" or "FR" for "fuse
resistor". They are likely to be located near to the bridge rectifier(s),
smoothing caps, and regulators.

The transistor type is very common. Virtually any general purpose NPN
transistor with Japanese pinning ( flat towards you, pins down, E-C-B ) will
do. The full type number for that transistor is 2SC1815.

Also, its a bit hard to see for sure, but does that electrolytic cap just
below and to the right of your red circle, have a slightly domed top ? If it
does, it may have been responsible for the demise of the transistor, and
will need to be replaced.

Arfa