uPC 1241H/uPC1242H/ECG7101

[Yukio YANO]

I am puzzled by a dead audio output stage using a uPC1242H ! DC
checks shows 12 Volts on Pin 8 (supply) but Pin 6 (audio OUT) shows 0
Volts (should be ~ 6 Volt ie 1/2 Supply), Pin 1 (audio IN) is 0 Volts
with ~ 1 V pp Audio
Pins 4/5 are at Grounded . Resistance Checks, Out of Circuit on New
IC's and compared to original are identical. Re-installation of new ICs
show exactly the same response 0 Volts on pin 6 ! There is not a hint of
a signal on pin 6, should show something even into a Dead Short.

What am I missing ? Pins 2,3,7 are all around 1~2 Volts.

Do I have Three Dead Chips !, I haven't seen that many failures at one
time in years ?

I always check for a bad Audio Output Chip by measuring the Audio Out
Pin and expect it run at about 1/2 Supply Voltage.

A circuit diagram would be nice, but I think the problem in "on chip" so
a diagram is really not that helpful.

I guess I am just having a bad day !!

Yukio TIA.

 

[ray13]

Wondering does that IC have a mute pin?

 

[Franc Zabkar]

I am puzzled by a dead audio output stage using a uPC1242H ! DC
checks shows 12 Volts on Pin 8 (supply) but Pin 6 (audio OUT) shows 0
Volts (should be ~ 6 Volt ie 1/2 Supply), Pin 1 (audio IN) is 0 Volts
with ~ 1 V pp Audio
Pins 4/5 are at Grounded . Resistance Checks, Out of Circuit on New
IC's and compared to original are identical. Re-installation of new ICs
show exactly the same response 0 Volts on pin 6 ! There is not a hint of
a signal on pin 6, should show something even into a Dead Short.

What do you mean by this? A dead short on the output should cause the
IC to shutdown (it has SC protection), so the output voltage would be
0. What do you measure if you isolate pin 6?

What am I missing ? Pins 2,3,7 are all around 1~2 Volts.

Do I have Three Dead Chips !, I haven't seen that many failures at one
time in years ?

I always check for a bad Audio Output Chip by measuring the Audio Out
Pin and expect it run at about 1/2 Supply Voltage.

-- Franc Zabkar

Please remove one 'i' from my address when replying by email.

 

[Arfa Daily]

I am puzzled by a dead audio output stage using a uPC1242H ! DC checks
shows 12 Volts on Pin 8 (supply) but Pin 6 (audio OUT) shows 0 Volts
(should be ~ 6 Volt ie 1/2 Supply), Pin 1 (audio IN) is 0 Volts with ~ 1 V
pp Audio
Pins 4/5 are at Grounded . Resistance Checks, Out of Circuit on New IC's
and compared to original are identical. Re-installation of new ICs show
exactly the same response 0 Volts on pin 6 ! There is not a hint of a
signal on pin 6, should show something even into a Dead Short.

What am I missing ? Pins 2,3,7 are all around 1~2 Volts.

Do I have Three Dead Chips !, I haven't seen that many failures at one
time in years ?

I always check for a bad Audio Output Chip by measuring the Audio Out Pin
and expect it run at about 1/2 Supply Voltage.

A circuit diagram would be nice, but I think the problem in "on chip" so a
diagram is really not that helpful.

I guess I am just having a bad day !!

Yukio TIA.

I might feel inclined to check the filter and bypass caps on pins 2 and 3
respectively, and the bootstrap cap between 6 and 7. There is no mute pin on
this IC. You might also try running it with pin 1 lifted, then see if you
can ' buzz ' it from this point.

Arfa