Old Technics tuner, anyone ... ?

A

Arfa Daily

Guest
I thought I had the manuals for just about every common item Technics ever
produced, but not this one ...

Anyone got a PDF of the schematic for a Technics ST-X990L. Particularly
interested in the bit around the PSU

The arfa.daily email address that this was posted from works, in case anyone
can help

TIA

Arfa
 
I don't know specifically, but will check my service manuals on CD for this one.
Any particular problem you are addressing? I may also have service bullitens.

Dan
 
HIFIENGINE.COM has teh ST-x999l model. Close enough? Create an account for yourself and look in the manual section under Technics (Panasonic is also there, but does not have these).

Dan
 
<dansabrservices@yahoo.com> wrote in message
news:48b671dc-89d3-403b-8142-5fd04178dd30@googlegroups.com...
I don't know specifically, but will check my service manuals on CD for
this one.
Any particular problem you are addressing? I may also have service
bullitens.

Dan
Click to expand...

It has no 'proper' output. A bit of hum-y noise and that's it. Display is
normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU
problem or maybe a rail getting dragged down somewhere by a leaky rail
decoupling cap as used to be common on all sorts of Pan gear back in the
day. I picked one of the IF processor chips at random and looked up the data
sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14 volts, but
there's actually only about 5 volts on the pin. I tried following the print
back, but it rapidly starts jumping around the board on wire links and print
'splits'. It's really not worth spending the time on trying to trace where
the rail comes from, and what decouplers are hanging across it, but it would
of course be a very simple fix with the benefit of a schematic. If all else
fails, I can get a download copy for $4.99 of the 'net, but cheapskate as I
am ... d;-)

Arfa
 
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:US59w.918017$cV1.639726@fx14.am4...
dansabrservices@yahoo.com> wrote in message
news:48b671dc-89d3-403b-8142-5fd04178dd30@googlegroups.com...
I don't know specifically, but will check my service manuals on CD for
this one.
Any particular problem you are addressing? I may also have service
bullitens.

Dan


It has no 'proper' output. A bit of hum-y noise and that's it. Display is
normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU
problem or maybe a rail getting dragged down somewhere by a leaky rail
decoupling cap as used to be common on all sorts of Pan gear back in the
day. I picked one of the IF processor chips at random and looked up the
data sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14 volts,
but there's actually only about 5 volts on the pin. I tried following the
print back, but it rapidly starts jumping around the board on wire links
and print 'splits'. It's really not worth spending the time on trying to
trace where the rail comes from, and what decouplers are hanging across
it, but it would of course be a very simple fix with the benefit of a
schematic. If all else fails, I can get a download copy for $4.99 of the
'net, but cheapskate as I am ... d;-)

Arfa
Click to expand...
Have you checked the power supply bulk capacitors for a high esr cap? Sure
sounds like it could be an issue.
 
<dansabrservices@yahoo.com> wrote in message
news:e49ef7cf-8d8a-4402-a0b5-7073089de4f1@googlegroups.com...
HIFIENGINE.COM has teh ST-x999l model. Close enough? Create an account
for yourself and look in the manual section under Technics (Panasonic is
also there, but does not have these).

Dan
Click to expand...

I've already got a HiFiEngine account. I'll go look. Thanks. In the meantime
I have been sent a photo by Nigel. Haven't had a chance to have a close look
at it yet to see if the voltages etc are readable

Arfa
 
"Tom Miller" <tmiller11147@verizon.net> wrote in message
news:m42tat$51u$1@dont-email.me...
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:US59w.918017$cV1.639726@fx14.am4...


dansabrservices@yahoo.com> wrote in message
news:48b671dc-89d3-403b-8142-5fd04178dd30@googlegroups.com...
I don't know specifically, but will check my service manuals on CD for
this one.
Any particular problem you are addressing? I may also have service
bullitens.

Dan


It has no 'proper' output. A bit of hum-y noise and that's it. Display is
normal. Appears to tune normally, but I'm sure it isn't. Looks like a PSU
problem or maybe a rail getting dragged down somewhere by a leaky rail
decoupling cap as used to be common on all sorts of Pan gear back in the
day. I picked one of the IF processor chips at random and looked up the
data sheet on it to find the Vcc pin. The sheet claimed a Vcc of 14
volts, but there's actually only about 5 volts on the pin. I tried
following the print back, but it rapidly starts jumping around the board
on wire links and print 'splits'. It's really not worth spending the time
on trying to trace where the rail comes from, and what decouplers are
hanging across it, but it would of course be a very simple fix with the
benefit of a schematic. If all else fails, I can get a download copy for
$4.99 of the 'net, but cheapskate as I am ... d;-)

Arfa
Have you checked the power supply bulk capacitors for a high esr cap? Sure
sounds like it could be an issue.
Click to expand...

First check, always. Nothing jumping out. Main rail off the reccy is there
and looks about as ripple-free as you would expect pre the regulators ...

Arfa
 
"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:Sf79w.133058$7w2.123520@fx01.am4...
"Tom Miller" <tmiller11147@verizon.net> wrote in message
news:m42tat$51u$1@dont-email.me...

"Arfa Daily" <arfa.daily@ntlworld.com> wrote in message
news:US59w.918017$cV1.639726@fx14.am4...


dansabrservices@yahoo.com> wrote in message
news:48b671dc-89d3-403b-8142-5fd04178dd30@googlegroups.com...
I don't know specifically, but will check my service manuals on CD for
this one.
Any particular problem you are addressing? I may also have service
bullitens.

Dan


It has no 'proper' output. A bit of hum-y noise and that's it. Display
is normal. Appears to tune normally, but I'm sure it isn't. Looks like a
PSU problem or maybe a rail getting dragged down somewhere by a leaky
rail decoupling cap as used to be common on all sorts of Pan gear back
in the day. I picked one of the IF processor chips at random and looked
up the data sheet on it to find the Vcc pin. The sheet claimed a Vcc of
14 volts, but there's actually only about 5 volts on the pin. I tried
following the print back, but it rapidly starts jumping around the board
on wire links and print 'splits'. It's really not worth spending the
time on trying to trace where the rail comes from, and what decouplers
are hanging across it, but it would of course be a very simple fix with
the benefit of a schematic. If all else fails, I can get a download copy
for $4.99 of the 'net, but cheapskate as I am ... d;-)

Arfa
Have you checked the power supply bulk capacitors for a high esr cap?
Sure sounds like it could be an issue.


First check, always. Nothing jumping out. Main rail off the reccy is there
and looks about as ripple-free as you would expect pre the regulators ...

Arfa
Click to expand...

Ok, yes. Knowing you, that was a dumb question. Good luck.
 
First check, always. Nothing jumping out. Main rail off the reccy is
there and looks about as ripple-free as you would expect pre the
regulators ...

Arfa

Ok, yes. Knowing you, that was a dumb question. Good luck.
Click to expand...

Why thank you kind sir ! Very nice of you to say so :)

Arfa
 
<dansabrservices@yahoo.com> wrote in message
news:80889e1d-f127-4731-ae74-da38da98616f@googlegroups.com...
I'll still look on the CDs too. Just thought of the website.

Dan
Click to expand...

Thanks Dan. Appreciate the effort.

Arfa
 
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