Old Technics tuner, anyone ... ?

Arfa Daily

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Nov 13, 2014, 8:04:18 AM11/13/14

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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

dansabr...@yahoo.com

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Nov 13, 2014, 10:58:35 AM11/13/14

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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

Arfa Daily

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Nov 13, 2014, 12:28:23 PM11/13/14

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<dansabr...@yahoo.com> wrote in message
news:48b671dc-89d3-403b...@googlegroups.com...

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

dansabr...@yahoo.com

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Nov 13, 2014, 1:04:04 PM11/13/14

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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

Tom Miller

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Nov 13, 2014, 1:30:04 PM11/13/14

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"Arfa Daily" <arfa....@ntlworld.com> wrote in message
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Have you checked the power supply bulk capacitors for a high esr cap? Sure
sounds like it could be an issue.

Arfa Daily

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Nov 13, 2014, 2:00:33 PM11/13/14

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<dansabr...@yahoo.com> wrote in message
news:e49ef7cf-8d8a-4402...@googlegroups.com...

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

Arfa Daily

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Nov 13, 2014, 2:03:18 PM11/13/14

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"Tom Miller" <tmille...@verizon.net> wrote in message
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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

Tom Miller

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Nov 13, 2014, 2:08:31 PM11/13/14

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"Arfa Daily" <arfa....@ntlworld.com> wrote in message

news:Sf79w.133058$7w2.1...@fx01.am4...

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

dansabr...@yahoo.com

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Nov 13, 2014, 2:34:39 PM11/13/14

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I'll still look on the CDs too. Just thought of the website.

Dan

Arfa Daily

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Nov 13, 2014, 5:32:18 PM11/13/14

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>>
>> 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.
>
>

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

Arfa

Arfa Daily

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Nov 13, 2014, 5:32:46 PM11/13/14

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<dansabr...@yahoo.com> wrote in message
news:80889e1d-f127-4731...@googlegroups.com...

> I'll still look on the CDs too. Just thought of the website.
>
> Dan
>

Thanks Dan. Appreciate the effort.

Arfa