Bad audio IC STK350-030

Guest
Trying to fix this Sony STR-D550Z AV receiver.

All of a sudden the left channel sounds "buzzy".
Not a hum, but the audio is broken up... sounds like a bad cap.
But in tracing the signal I came across this IC STK350-030 that is running
really hot... too hot to touch for very long and it's not on a heatsink...
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.

Anyone ever have dealings with this chip? I found a datasheet at
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

I'm about to order the part but I'm wondering if the IC took down any
associated parts next to it.

--
Skip
 
Change the IC for reliability, and before putting the power back, find the
possible cause of this condition.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
=========================================


<Skip> wrote in message news:bv65430f9j@enews3.newsguy.com...
Trying to fix this Sony STR-D550Z AV receiver.

All of a sudden the left channel sounds "buzzy".
Not a hum, but the audio is broken up... sounds like a bad cap.
But in tracing the signal I came across this IC STK350-030 that is running
really hot... too hot to touch for very long and it's not on a heatsink...
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.

Anyone ever have dealings with this chip? I found a datasheet at
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

I'm about to order the part but I'm wondering if the IC took down any
associated parts next to it.

--
Skip
 
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.
Click to expand...
Barring dry joints, I'm going to guess it IS a bad cap, which your
finger is temporarily replacing. What does the pin in question lead
to?
 
Thanks for posting.

There's a network of caps and resistors coming off those pins. Probably
filter and pull-down etc. There are some polar electrolytics and some
non-polar ceramics. I ordered a new IC and I'm going to unsolder it tonight
and check resistances an the board with the IC out of the circuit. Then I'll
check resistances on the IC.

The IC is a 15-pin flat package with GND at pin 8 in the middle and the rest
of the pins are symmetrical with left and right channels.

Good datasheet at:
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

Basically it's:

Pin
1 + IN
2 - IN
3 +
4 - (minus)
5 - OUT
6 +OUT
7 -VCC
8 GND
9 +VCC
10 + OUT
11 - OUT
12 - (minus)
13 +
14 - IN
15 + IN

--
Skip


"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:608b6569.0401271339.52c539d@posting.google.com...
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.

Barring dry joints, I'm going to guess it IS a bad cap, which your
finger is temporarily replacing. What does the pin in question lead
to?
Click to expand...
 
I replace them all the time, but usually for a DC problem which puts the
receiver into PROTECT mode. I don't remember them running especially hot. Is
there another in that piece to compare it to?

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


<Skip> wrote in message news:bv65430f9j@enews3.newsguy.com...
Trying to fix this Sony STR-D550Z AV receiver.

All of a sudden the left channel sounds "buzzy".
Not a hum, but the audio is broken up... sounds like a bad cap.
But in tracing the signal I came across this IC STK350-030 that is running
really hot... too hot to touch for very long and it's not on a heatsink...
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.

Anyone ever have dealings with this chip? I found a datasheet at
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

I'm about to order the part but I'm wondering if the IC took down any
associated parts next to it.

--
Skip
Click to expand...
 
Thanks for posting.

There's an STK350-230 toward the rear near the inputs that was running about
as warm as the STK350-030... I may have been wrong in my guess on the IC
being bad.

I pulled out the STK350-030 and removed the tuner/preamp board from the
chassis so I could read the values on the caps but so far can't find
anything out of whack in the electrolytics but still looking.

By any chance do you have a schematic for this thing?

All I have to go by now is the data sheet at:
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

Not sure how closely Sony adhered to that design.

--
Skip


"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:bv73of$omir3$1@ID-180484.news.uni-berlin.de...
I replace them all the time, but usually for a DC problem which puts the
receiver into PROTECT mode. I don't remember them running especially hot.
Is
there another in that piece to compare it to?

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


Skip> wrote in message news:bv65430f9j@enews3.newsguy.com...
Trying to fix this Sony STR-D550Z AV receiver.

All of a sudden the left channel sounds "buzzy".
Not a hum, but the audio is broken up... sounds like a bad cap.
But in tracing the signal I came across this IC STK350-030 that is
running
really hot... too hot to touch for very long and it's not on a
heatsink...
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.

Anyone ever have dealings with this chip? I found a datasheet at
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

I'm about to order the part but I'm wondering if the IC took down any
associated parts next to it.

--
Skip
Click to expand...
 
You might try measuring across the base-emitter junctions of the output
transistors and compare to the other channels. Correct reading would be
about 1.2 volts, since they are Darlington transistors.

Common problems NOT caused by blown outputs or the STK are few, so if the
outputs are OK, then there's at least a good chance the STK will fix your
problem.

Do check the large white emitter resistor, the small fusible resistors (10
and 180 ohms), and the small transistors.


Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


<Skip> wrote in message news:bv756102g9d@enews4.newsguy.com...
Thanks for posting.

There's an STK350-230 toward the rear near the inputs that was running
about
as warm as the STK350-030... I may have been wrong in my guess on the IC
being bad.

I pulled out the STK350-030 and removed the tuner/preamp board from the
chassis so I could read the values on the caps but so far can't find
anything out of whack in the electrolytics but still looking.

By any chance do you have a schematic for this thing?

All I have to go by now is the data sheet at:
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

Not sure how closely Sony adhered to that design.

--
Skip


"Mark D. Zacharias" <mzacharias@yis.us> wrote in message
news:bv73of$omir3$1@ID-180484.news.uni-berlin.de...
I replace them all the time, but usually for a DC problem which puts the
receiver into PROTECT mode. I don't remember them running especially
hot.
Is
there another in that piece to compare it to?

Mark Z.

--
Please reply only to Group. I regret this is necessary. Viruses and spam
have rendered my regular e-mail address useless.


Skip> wrote in message news:bv65430f9j@enews3.newsguy.com...
Trying to fix this Sony STR-D550Z AV receiver.

All of a sudden the left channel sounds "buzzy".
Not a hum, but the audio is broken up... sounds like a bad cap.
But in tracing the signal I came across this IC STK350-030 that is
running
really hot... too hot to touch for very long and it's not on a
heatsink...
if I run a finger across the 15 pins, when my finger reaches one end
of
these pins, the audio clears up for a second before fading out.

Anyone ever have dealings with this chip? I found a datasheet at
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

I'm about to order the part but I'm wondering if the IC took down any
associated parts next to it.

--
Skip
Click to expand...
 
Change just the STK....and do a real good resoldering of all the high temp
areas , you will find many connections with ring cracks!


--
==========================
Jeff Stielau
Shoreline Electronics Repair
344 East Main Street
Clinton,CT 06413
860-399-1861
860-664-3535 (fax)
jstielau@snet.net
========================
"If you push something hard enough it will fall over."
Fudd's First Law of Opposition - Sir Sidney Fudd


<Skip> wrote in message news:bv65430f9j@enews3.newsguy.com...
Trying to fix this Sony STR-D550Z AV receiver.

All of a sudden the left channel sounds "buzzy".
Not a hum, but the audio is broken up... sounds like a bad cap.
But in tracing the signal I came across this IC STK350-030 that is running
really hot... too hot to touch for very long and it's not on a heatsink...
if I run a finger across the 15 pins, when my finger reaches one end of
these pins, the audio clears up for a second before fading out.

Anyone ever have dealings with this chip? I found a datasheet at
http://www.datasheetcatalog.com/datasheet/S/STK350-030.shtml

I'm about to order the part but I'm wondering if the IC took down any
associated parts next to it.

--
Skip
Click to expand...
 
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