[TechAssist] Re: FW: JVC AV31BM6 Weird Startup Problem FIXED
- From: "art bevilacqua" <abevilac@xxxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Sat, 18 Jan 2003 16:02:47 -0500
The proper transistors arrived, and we replaced Q922 and Q924 and that
fixed it. Odd though how both original transistors would function in
Q922's position, but neither would work as Q924.
Art Bevilacqua
Essex Radio and TV
40 Main Street
Essex, MA 01929
-----Original Message-----
From: techassist-bounce@xxxxxxxxxxxxx
[mailto:techassist-bounce@xxxxxxxxxxxxx] On Behalf Of art bevilacqua
Sent: Wednesday, January 15, 2003 10:33 PM
To: techassist@xxxxxxxxxxxxx
Subject: [TechAssist] FW: JVC AV31BM6 Weird Startup Problem
This set won't start up, but the deguasser relay clicks. I've traced
the on/off signal from the microprocessor: it's 4.7 volt on signal
passes through a 1K resistor and hits the "base" of two digital
transistors, Q922 to energize the 130Volt relay, and Q924 to switch 12V.
With an on command, the voltage downstream of the 1k resistor only gets
up to 1.3 volts, which seems to be enough to switch Q924, but is not
enough to pull Q922 in enough to pick up the relay (the collector only
gets down to 6 volts, leaving about 3 or 4 across the relay coil).
If I short the collector of Q922 to ground for a second the relay picks
up
and the set runs perfectly: all power supply voltages are perfect and
picture and sound are perfect.
If I only lift the base of Q924, the base of Q922 goes to 4.4 volts and
the
130V relay picks up. If I only lift the base of Q922, the base of Q924
is still 1.3. A small trace connects the 1K source resistor to both Q922
and Q924 bases.
The odd thing is that I've rotated the three digital transistors Q922,
Q924, and Q921 (degauss) into each other's positions on the board and
get the exact same response: Whichever of the three transistors is in
the Q924 position always seems to pull down the on/off signal - again,
regardless of which transistor is in place.
The digital transistors are DTC114's (ECG 2355). We have some new ones
coming but this bugs me and I thought I check for anyone's other ideas.
Thanks
Art Bevilacqua
Essex Radio and TV
40 Main Street
Essex, MA 01929
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