[TechAssist] Re: One for the books !
- From: "Christopher Barnak" <cbarnak@xxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 08 Dec 2003 09:42:05 -0500
Keith,
My gut instinct is that the 47k is right. It works on the other
channel, and it worked on the bad channel before the problem developed.
I think the 1.8k sub just goes around the real problem. Watch for a
leaky capacitor, not high ESR, but leakage (lower ohms) with your
ohmeter accross it. That may be whats throwing off the bias level. Just
guessing.
Christopher Barnak, CET
Norfolk Public Schools
School Plant Facilities
966 Bellmore Ave.
Norfolk, Va. 23504
Phone 757 628 3385
Fax 757 628 3392
cbarnak@xxxxxxxxxxxxx
>>> keith@xxxxxxxxxxxxxxxxxx 12/5/03 11:58:17 AM >>>
Pioneer A/V surround receiver model # VSX-D307 . Problem : In the front
left
channel audio was very distorted. Injection of sinewave showed that
the
negative going portion was clipped off completely. Checked my rail
voltages
to the PAC007 IC's and everything looked good. Sinewave going in was
good
too. Ordered a new PAC007 ......didn't fix it. Really pulled my hair
out on
this one. Turned out, an incorrect value resistor FROM THE FACTORY had
been
installed at location R483. Schematic called for 1.8k and unit had a
47k in
it's place. Parts list didn't even list this part. It is part of the
constant current source for the negative going amplifier inside the
PAC007
location IC402. Here is the kicker : in the other channel, the part in
the
same location, doing the same job in the circuit, is a 47K ! And that
is
what the schematic calls for ! Yes it is the same PAC007 and ALL of
the
peripheral circuitry is the same. Go figure ! Anybody seen this before
? Or
am I going nuts ?
Keith Trumbla
BEM Electronics Inc.
Suite 212-530 Century St.
WPG. MB. R3H 0Y4 Canada
Ph.204.775.2875 Fax.204.774.9192
www.bemelectronics.com
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