I've owned this receiver/amp for 30 years. Used infrequently but functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on low
setting. Toggled to mute, loudness, no joy. Using FM input, controls seem
to work and I can hear music when I reach very high settings. Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on low
setting. Toggled to mute, loudness, no joy. Using FM input, controls seem
to work and I can hear music when I reach very high settings. Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?

Not shorted.
I thought of that and attached different speakers and same result.
Sound comes out of both speakers, balance controls function, mute button
drops volumne as it should.
Output meter and audible output simply dropped to marginal. [Vol on max
should be overpoweringly loud, it is now a whisper.]
Both channels equally effected.
There are perhaps 6 fuses. I removed and reset just in case they were
oxidized. No joy.
Other suggestions welcomed.


"Smitty Two" wrote in message
news
In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings. Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?

Digging a little deeper, I can see a relay on the power amp board. I assume
this is part of the output protection circuit. If this were the issue,
would I have any sound at all? Sound is present, just extremely low. I
haven't yet checked voltages. [Not a switching mode PS - large, very heavy
transformer circuit.]




"John Keiser" wrote in message
...
Not shorted.
I thought of that and attached different speakers and same result.
Sound comes out of both speakers, balance controls function, mute button
drops volumne as it should.
Output meter and audible output simply dropped to marginal. [Vol on max
should be overpoweringly loud, it is now a whisper.]
Both channels equally effected.
There are perhaps 6 fuses. I removed and reset just in case they were
oxidized. No joy.
Other suggestions welcomed.


"Smitty Two" wrote in message
news
In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on
low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings. Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?

Unit has a jumper connecting preamp to amp. Signal injected to power amp is
perfect. Not the power stage after all.

Preamp seems to respond, balance, volumne, mute circuit wise but output must
be severely reduced.

Any suggestions?






"John Keiser" wrote in message
...
Digging a little deeper, I can see a relay on the power amp board. I
assume this is part of the output protection circuit. If this were the
issue, would I have any sound at all? Sound is present, just extremely
low. I haven't yet checked voltages. [Not a switching mode PS - large,
very heavy transformer circuit.]




"John Keiser" wrote in message
...
Not shorted.
I thought of that and attached different speakers and same result.
Sound comes out of both speakers, balance controls function, mute button
drops volumne as it should.
Output meter and audible output simply dropped to marginal. [Vol on max
should be overpoweringly loud, it is now a whisper.]
Both channels equally effected.
There are perhaps 6 fuses. I removed and reset just in case they were
oxidized. No joy.
Other suggestions welcomed.


"Smitty Two" wrote in message
news
In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on
low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings.
Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?

John Keiser wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings. Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.




If both channels affected then suggests protect cct. Test the voltages on
any zeners associated with that cct , drifting with age, and altering the
sense-window

John Keiser wrote in message
...
Digging a little deeper, I can see a relay on the power amp board. I
assume
this is part of the output protection circuit. If this were the issue,
would I have any sound at all? Sound is present, just extremely low. I
haven't yet checked voltages. [Not a switching mode PS - large, very
heavy
transformer circuit.]




"John Keiser" wrote in message
...
Not shorted.
I thought of that and attached different speakers and same result.
Sound comes out of both speakers, balance controls function, mute button
drops volumne as it should.
Output meter and audible output simply dropped to marginal. [Vol on max
should be overpoweringly loud, it is now a whisper.]
Both channels equally effected.
There are perhaps 6 fuses. I removed and reset just in case they were
oxidized. No joy.
Other suggestions welcomed.


"Smitty Two" wrote in message
news
In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on
low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings.
Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but
I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?





The sense range monitoring the +/- rails ,or the rails themselves, have
drifted out of kilter. Load the high one a bit, then the other, to see if
it kicks life into the amp. Monitor some zener voltages, and balance up a
bit, if that fails to ellicit anything

"John Keiser" wrote in message
news:j5mdndbY58Q3Fq7TnZ2dnUVZ_i2dnZ2d@powerusenet. com...
Unit has a jumper connecting preamp to amp. Signal injected to power amp
is perfect. Not the power stage after all.

Preamp seems to respond, balance, volumne, mute circuit wise but output
must be severely reduced.

Any suggestions?






"John Keiser" wrote in message
...
Digging a little deeper, I can see a relay on the power amp board. I
assume this is part of the output protection circuit. If this were the
issue, would I have any sound at all? Sound is present, just extremely
low. I haven't yet checked voltages. [Not a switching mode PS - large,
very heavy transformer circuit.]




"John Keiser" wrote in message
...
Not shorted.
I thought of that and attached different speakers and same result.
Sound comes out of both speakers, balance controls function, mute button
drops volumne as it should.
Output meter and audible output simply dropped to marginal. [Vol on max
should be overpoweringly loud, it is now a whisper.]
Both channels equally effected.
There are perhaps 6 fuses. I removed and reset just in case they were
oxidized. No joy.
Other suggestions welcomed.


"Smitty Two" wrote in message
news In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on
low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings.
Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but
I have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?







Make sure the tape monitor button is not engaged. TURN THE VOLUME DOWN prior
to pressing this button. Also, it wouldn't hurt to try pressing and
manipulating the various controls to see if any of them might be cutting
out.

Mark Z.

Tape monitor toggles as expected.
Not the problem.
Still output remains low.


"Mark Zacharias" wrote in message
.com...
"John Keiser" wrote in message
news:j5mdndbY58Q3Fq7TnZ2dnUVZ_i2dnZ2d@powerusenet. com...
Unit has a jumper connecting preamp to amp. Signal injected to power amp
is perfect. Not the power stage after all.

Preamp seems to respond, balance, volumne, mute circuit wise but output
must be severely reduced.

Any suggestions?






"John Keiser" wrote in message
...
Digging a little deeper, I can see a relay on the power amp board. I
assume this is part of the output protection circuit. If this were the
issue, would I have any sound at all? Sound is present, just extremely
low. I haven't yet checked voltages. [Not a switching mode PS - large,
very heavy transformer circuit.]




"John Keiser" wrote in message
...
Not shorted.
I thought of that and attached different speakers and same result.
Sound comes out of both speakers, balance controls function, mute
button drops volumne as it should.
Output meter and audible output simply dropped to marginal. [Vol on
max should be overpoweringly loud, it is now a whisper.]
Both channels equally effected.
There are perhaps 6 fuses. I removed and reset just in case they were
oxidized. No joy.
Other suggestions welcomed.


"Smitty Two" wrote in message
news In article ,
"John Keiser" wrote:

I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on
low
setting. Toggled to mute, loudness, no joy. Using FM input,
controls seem
to work and I can hear music when I reach very high settings.
Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but
I have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Speaker wires shorted?







Make sure the tape monitor button is not engaged. TURN THE VOLUME DOWN
prior to pressing this button. Also, it wouldn't hurt to try pressing and
manipulating the various controls to see if any of them might be cutting
out.

Mark Z.

Without a schematic I am fairly clueless.
PS voltages are 10, 18.75 and 57.75. Not sure if that's within specs. [A
different Pioneer SX model called for 65V.]
These PCboards are complete unmarked.
Digital vol control goes to "31". At "31" the digital output meter shows
maybe "1 watt" peak on a scale to 150. Very audible, but a fraction of what
it should be. I normally keep the vol @ "8".



"N_Cook" wrote in message
...
John Keiser wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings. Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.




If both channels affected then suggests protect cct. Test the voltages on
any zeners associated with that cct , drifting with age, and altering the
sense-window

John Keiser wrote in message
news:rOadnRuD9YiIo6nTnZ2dnUVZ_t2dnZ2d@powerusenet. com...
Without a schematic I am fairly clueless.
PS voltages are 10, 18.75 and 57.75. Not sure if that's within specs. [A
different Pioneer SX model called for 65V.]
These PCboards are complete unmarked.
Digital vol control goes to "31". At "31" the digital output meter shows
maybe "1 watt" peak on a scale to 150. Very audible, but a fraction of
what
it should be. I normally keep the vol @ "8".



"N_Cook" wrote in message
...
John Keiser wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned
fine. Today, while playing a CD, suddenly stopped after 5 minutes on
low
setting. Toggled to mute, loudness, no joy. Using FM input, controls
seem
to work and I can hear music when I reach very high settings.
Sometimes
crackles to very loud but only momentary. I think pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have
no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.




If both channels affected then suggests protect cct. Test the voltages
on
any zeners associated with that cct , drifting with age, and altering
the
sense-window





no -ve rail/s ?

I now see that vol is almost mute with equalizer [bass and treble] controls
flat or neg.
With equalizer set to max, vol is useable @ perhaps 80% power.
Does that help pinpoint the problem?

"John Keiser" wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned fine. Today, while playing a CD, suddenly stopped after 5
minutes on low setting. Toggled to mute, loudness, no joy. Using FM
input, controls seem to work and I can hear music when I reach very high
settings. Sometimes crackles to very loud but only momentary. I think
pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.

Could you please not top post, John ? It makes it very difficult to see what
it is that you are replying to. The usenet convention is to bottom post.

Cheers

Arfa

On 7/30/2011 10:23 AM, John Keiser wrote:
Without a schematic I am fairly clueless.
PS voltages are 10, 18.75 and 57.75. Not sure if that's within specs. [A
different Pioneer SX model called for 65V.]
These PCboards are complete unmarked.
Digital vol control goes to "31". At "31" the digital output meter shows
maybe "1 watt" peak on a scale to 150. Very audible, but a fraction of what
it should be. I normally keep the vol @ "8".



Did you try here for the manual?:
http://www.hifi-manuals.com/Download/Pioneer/SX-8-service-manual

"John Keiser" wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned fine. Today, while playing a CD, suddenly stopped after 5
minutes on low setting. Toggled to mute, loudness, no joy. Using FM
input, controls seem to work and I can hear music when I reach very high
settings. Sometimes crackles to very loud but only momentary. I think
pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have no schematic. Before I tear in blindly, does anyone have access to a
schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.


The service manual is available for free here

http://www.hifi-manuals.com/Pioneer

You need to create an account, but it costs nothing. Your problem sounds
possibly power supply related to me. Mr Cook quesried the fact that you do
not appear to be recording any low negative rails, and that would also be a
concern to me. If you look on the first schematic towards the top left of
the enclosed area marked "POWER SUPPLY CIRCUIT", you will see a pair of low
rails (+ / - 15 v ) marked

"( EQ.AMP TONE CONT. VCA IC) " The +15 v reg is a 3 terminal 78 series,
but the negative regulator is discrete, constructed around a pair of
transistors. I would suggest that it might be a good idea to check that
those rails are both present, and finding their way to the indicated bits of
circuitry. Now comes the tricky bit. The schematic, although a perfectly
complete and valid looking one, sadly has no component refs on it, which is
going to make finding those devices a bit more of a hunting trip, than would
otherwise be necessary. Strangely, however, the PCB overlay diagrams are
fully annotated ...

Arfa

Perfect. I hadn't found that.
Thank you!


"Sofa Slug" wrote in message
...
On 7/30/2011 10:23 AM, John Keiser wrote:
Without a schematic I am fairly clueless.
PS voltages are 10, 18.75 and 57.75. Not sure if that's within specs.
[A
different Pioneer SX model called for 65V.]
These PCboards are complete unmarked.
Digital vol control goes to "31". At "31" the digital output meter shows
maybe "1 watt" peak on a scale to 150. Very audible, but a fraction of
what
it should be. I normally keep the vol @ "8".



Did you try here for the manual?:
http://www.hifi-manuals.com/Download/Pioneer/SX-8-service-manual

"Arfa Daily" wrote in message
...


"John Keiser" wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned fine. Today, while playing a CD, suddenly stopped after 5
minutes on low setting. Toggled to mute, loudness, no joy. Using FM
input, controls seem to work and I can hear music when I reach very high
settings. Sometimes crackles to very loud but only momentary. I think
pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have no schematic. Before I tear in blindly, does anyone have access to
a schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.


The service manual is available for free here

http://www.hifi-manuals.com/Pioneer

You need to create an account, but it costs nothing. Your problem sounds
possibly power supply related to me. Mr Cook quesried the fact that you do
not appear to be recording any low negative rails, and that would also be
a concern to me. If you look on the first schematic towards the top left
of the enclosed area marked "POWER SUPPLY CIRCUIT", you will see a pair of
low rails (+ / - 15 v ) marked

"( EQ.AMP TONE CONT. VCA IC) " The +15 v reg is a 3 terminal 78 series,
but the negative regulator is discrete, constructed around a pair of
transistors. I would suggest that it might be a good idea to check that
those rails are both present, and finding their way to the indicated bits
of circuitry. Now comes the tricky bit. The schematic, although a
perfectly complete and valid looking one, sadly has no component refs on
it, which is going to make finding those devices a bit more of a hunting
trip, than would otherwise be necessary. Strangely, however, the PCB
overlay diagrams are fully annotated ...

Arfa

Sorry about top/bottom posting thing. Maybe this is on the bottom? I just
use OE to read, rarely post.

The schematic is complex but a big leg up.

Thank you all.

..

"John Keiser" wrote in message
...

"Arfa Daily" wrote in message
...


"John Keiser" wrote in message
news:48qdnVyu_aVeyq7TnZ2dnUVZ_qadnZ2d@powerusenet. com...
I've owned this receiver/amp for 30 years. Used infrequently but
functioned fine. Today, while playing a CD, suddenly stopped after 5
minutes on low setting. Toggled to mute, loudness, no joy. Using FM
input, controls seem to work and I can hear music when I reach very high
settings. Sometimes crackles to very loud but only momentary. I think
pre-amp is OK.
I'm thinking some sort of protective output circuit has activated but I
have no schematic. Before I tear in blindly, does anyone have access to
a schematic for this [I found a source on rapidshare but file no longer
there].
Thank you.


The service manual is available for free here

http://www.hifi-manuals.com/Pioneer

You need to create an account, but it costs nothing. Your problem sounds
possibly power supply related to me. Mr Cook quesried the fact that you
do not appear to be recording any low negative rails, and that would also
be a concern to me. If you look on the first schematic towards the top
left of the enclosed area marked "POWER SUPPLY CIRCUIT", you will see a
pair of low rails (+ / - 15 v ) marked

"( EQ.AMP TONE CONT. VCA IC) " The +15 v reg is a 3 terminal 78
series, but the negative regulator is discrete, constructed around a pair
of transistors. I would suggest that it might be a good idea to check
that those rails are both present, and finding their way to the indicated
bits of circuitry. Now comes the tricky bit. The schematic, although a
perfectly complete and valid looking one, sadly has no component refs on
it, which is going to make finding those devices a bit more of a hunting
trip, than would otherwise be necessary. Strangely, however, the PCB
overlay diagrams are fully annotated ...

Arfa

Sorry about top/bottom posting thing. Maybe this is on the bottom? I just
use OE to read, rarely post.

The schematic is complex but a big leg up.

Thank you all.

.

Yes, it does look a complex schematic, but at least it's in pdf format, so
fully scalable. Are you aware of the 'tile large pages' option that is often
offered by printer drivers ? This allows you to print the diagram over four
or six or how ever many you like pages, complete with a user definable
overlap, and cutting marks if you want them. This allows you to print a
complex one page diagram like this, at any size that suits you like A3 or
A2. With the overlap and cutting marks, it is a breeze to then tape it
together into a single large sheet.

On the top / bottom posting thing, yes, your last is conventionally
bottom-posted. It just makes it a lot easier to follow a long thread with a
lot of replies from different people, if everyone is following the same
posting scheme. It's different with replying to emails, because it's only
between two people, and each already knows what the other last said, so
top-replying is convenient for that.

Good luck with the Pioneer. It would be interesting to know what you find in
the end.

Arfa

Hi-fi engine!

Hi-fi engine!

On 31/01/16 20:51, wrote:
Hi-fi engine!


If you mention Hi-fi engine just once more you'll get smacked...

--
Adrian C