Re: Amplifier Problem - ***SOLVED***

In article 
<8355664a-be99-4169-940f-4314e360b300@[EMAIL PROTECTED]
>,
 EADGBE <hwbosshoss@[EMAIL PROTECTED]
> wrote:

> Good News!
> 
> This headphone amplifier has been REPAIRED and is now working
> perfectly.
> 
> Here's what happened:
> 
> I have been taking parallel measurements between the "good" and "bad"
> channels since the beginning.
> 
> I took voltage measurements, resistance measurements, tested ALL
> capacitors, and tested ALL transistors.
> 
> But someone in my original thread (I can't remember who offhand --
> sorry) did mention checking the circuit board traces.
> 
> "No need," I thought.  "The circuit board and all solder joints look
> fine to me."
> 
> But in a fit of desperation, I nonetheless decided to whip out a
> tester I hadn't used yet: my magnifying glass.
> 
> That's when I found it -- a *microscopic* crack in the trace between
> the emitter of Q208 and its adjoining 3.3 ohm resistor.  The crack was
> so incredibly tiny that I easily overlooked it--repeatedly.
> 
> I took one of my jumper leads and clipped one end of it to Q208's
> emitter and the other end of it to the 3.3 ohm resistor.
> 
> I then took voltage measurements.  EVERYTHING WAS NOW ON SPEC:
> 
> Q205's collector now measures +7.09V, and Q206 now has the following
> measurements:
> B: +6.51V
> C: +7.08V
> E: +5.84V
> 
> I was able to bridge the crack with a well-placed solder trail, and
> the headphone amp now sounds great.

You should *always* bridge the crack with a strand or two of fine wire; 
that'll keep it from cracking again, Real Soon Now.

Isaac