[TechAssist] Re: FW: JVC AV31BM6 Weird Startup Problem
- From: Cliff Afflick <sgt.cliff@xxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Wed, 15 Jan 2003 21:46:38 -0700
Hi Art.
Very interesting.
Change the 12v zener diode.could be d 927.
That might be the problem.
Cliff.
Double Zero
Electronics.
The trouble shooter.
sgt.cliff@xxxxxxx
----- Original Message -----
From: "art bevilacqua" <abevilac@xxxxxxxxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Wednesday, January 15, 2003 8:33 PM
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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