Pioneer SX-8
John Keiser
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.
Smitty Two
"John Keiser" <john.k...@hawaiiantel.net> wrote:
Speaker wires shorted?
John Keiser
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" <prest...@earthlink.net> wrote in message
news:prestwhich-ADF58...@news.eternal-september.org...
John Keiser
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" <john.k...@hawaiiantel.net> wrote in message
news:5NmdnbDP9bId-q7T...@powerusenet.com...
John Keiser
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" <john.k...@hawaiiantel.net> wrote in message
news:Ju2dnWMxl-aB567T...@powerusenet.com...
N_Cook
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
N_Cook
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
Mark Zacharias
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.
John Keiser
Not the problem.
Still output remains low.
"Mark Zacharias" <mark_za...@labolgcbs.net> wrote in message
news:4e33df0b$0$21936$a826...@newsreader.readnews.com...
John Keiser
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" <div...@tcp.co.uk> wrote in message
news:j10b9c$ben$1...@dont-email.me...
N_Cook
no -ve rail/s ?
John Keiser
flat or neg.
With equalizer set to max, vol is useable @ perhaps 80% power.
Does that help pinpoint the problem?
"John Keiser" <john.k...@hawaiiantel.net> wrote in message
news:48qdnVyu_aVeyq7T...@powerusenet.com...
Arfa Daily
it is that you are replying to. The usenet convention is to bottom post.
Cheers
Arfa
Sofa Slug
> 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
"John Keiser" <john.k...@hawaiiantel.net> wrote in message
news:48qdnVyu_aVeyq7T...@powerusenet.com...
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
John Keiser
Thank you!
"Sofa Slug" <sofa...@invalid.invalid> wrote in message
news:j12912$jdh$1...@dont-email.me...
John Keiser
"Arfa Daily" <arfa....@ntlworld.com> wrote in message
news:lJ1Zp.16040$Zm3....@newsfe11.ams2...
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.
.
>
Arfa Daily
"John Keiser" <john.k...@hawaiiantel.net> wrote in message
news:EaudnX-Zg4s1J6nT...@powerusenet.com...
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
schoe...@gmail.com
schoe...@gmail.com
Adrian Caspersz
> Hi-fi engine!
>
If you mention Hi-fi engine just once more you'll get smacked...
--
Adrian C