Sorry, thought I remembered output IC's from a previous post. Nevermind
that. The DC level you measured is still wrong for that channel, and is
associated with the two nearest output transistors (not IC's, sorry).

The transistors themselves are likely OK, since a failure there would
probably NOT give some intermediate voltage. I'd look for a bad resistor or
capacitor. More difficult if you're not a regular technician, but that's my
take on the situation.

Mark Z.


"jay heldman" wrote in message
news:mIC7d.293585$mD.246346@attbi_s02...
not sure I have identified output IC. underneath the metal heatsync,
which
runs across the width of the amp, are four o/p transistors (3 legs each).
how would one test the transistor to determine its status? is any of
these
o/p transistors also known as o/p IC?

of the 4 o/p transistors, two are black -labeled 2SC2525, and two are
green -labeled 2SC2525

so, are these transistors also called IC? and how to verify one is fault?
would one of the o/p transistor (being bad by itself) cause the amp's
output
to speakers to be none?

Thank you.



"Mark D. Zacharias" wrote in message
...
One would conclude the problem is on the channel where that 20 volts was
measured. Probably that output IC, though there could be another problem.
Solder connections, a bad resistor or capacitor, etc.

Mark Z.


"jay heldman" wrote in message
news:Zxo7d.159257$D%.83519@attbi_s51...
being careful not to short any two legs, attached voltmeter to the
center
leg of ceramic resistor packs labeled RGC55 0.47ohms KX2 2D. Facing
the
unit from the front and reaching inside, the resistor pack on right
reads
20V, the resistor pack on left reads zero. The metal heat sync seems
to
be
warmer on the right side (as viewed from in front and reaching inside)
with
the outside (black -labeled 2SC2525) seeming to be generating most
heat.

what might one conclude based on the left resistor pack reading no
voltage,
right resistor pack reading 20V, and seeming more heat generated by
right
side ??

Thank you.


"JVC Dude" wrote in message
...
yes those 2SA, 2SC devices are the output transistors, the black Ics
you
referred to, are something else.

What is getting hot? the main alloy heatsink? back to my orig post,
can
you
identify where the heat is coming from?

the source you quote does have some relation to your fault, but
excessive
current isn't the only way to 'open the relay', a DC offset on the
output
due to a failed o/p transistor will do the same.

I still advise against having a go yourself, but 2 o/ps are for left
channel, the other 2 for the right. its likely only 1 channel is duff.
Normally we would replace the 2 from 1 channel as a pair sine you
can't
tell
whether one may be weakened by the other failing.
as a test you may try carefully and without shorting any 2 metal
points
together, using a voltmeter with the black wire to metal sub
chassis/heatsink, see if you can measure a high voltage, say +50v
or -50v
on
the middle of the 3 legs of the rectangular white ceramic resistor
pack
with
the red probe. Set the meter to above 50 volts DC range- ideally a
digital
meter. the resistors are1 inch wide 1/4" thck, 3/4" high with 0.22
ohms
(omega symbol) on them

if you can't measure and voltage on either then your fault is probably
elsewhere, but I suspect you will measure a high (rail) voltage

Once again, if you don't know what you're doing don't try it, theres
some
high voltages knocking around and its easy to short together 2 metal
contacts and make yourself a nice smoke generator.

As someone put it the other day, all the magic blue smoke is
released
from the transistors!

good luck
AW