On Wed, 23 May 2012 18:49:23 -0500, "Dave" wrote:
"Jim Thompson" wrote in
message ...
On Wed, 23 May 2012 17:36:23 -0500, "Dave" wrote:
"Jim Thompson" wrote
in
message ...
On Wed, 23 May 2012 15:40:17 -0500, "Dave" wrote:
Posted a while back about a project I am trying to concoct- an intercom
for
my front door- and have made some progress. Unfortunately I hit a speed
bump when I added transistor Q4. Now it only gives me noise at the
output,
and lots and lots of that. Capacitors are all 100uF 35V, which I am
thinking may be the problem (maybe the last couple need to be 50 or
75V?)
Originally thought I might be overdriving Q4, so I replaced it with a
2N5296
from my junkbox, but that just doubled the volume of the noisy output.
If
anyone sees something I should but don't, please post. The only thing I
can
think of is upping the voltage on C8 and C9.
Any help is *greatly* appreciated...
Dave
Back up and do a little math. Calculate the bias current in that last
stage. (In fact, calculate all your stage biases.)
How much voltage gain do you need?
What is the load impedance? Is it a speaker?
...Jim Thompson
--
Bias *current*? When I think of biasing I think of voltage. Do you mean
collector current? I'm thinking it's around 180 mA. And after th first
three stages, I'm thinking voltage gain isn't lacking. Load is an 8 Ohm
speaker, which *seems* to be functioning fine. Only problem is the buzzing
that fills the air when I turn it on (which makes me think I have a
capacitor breaking down). Don't mean to be critical, but these seem like
very generic questions. What, specifically, are you thinking?
Thanks,
Dave.
I guess you don't need any help... you already know it all.
...Jim Thompson
--
Sorry. But if you weren't giving me complete and utter bull****, you
wouldn't be so offended when I pointed it out.
Dave
Ask anyone but a Larkin boot-licker... you don't know WTF you're
doing. You're just pasting crap together. That's why you failed the
simple bias question. Why can't you make it work?
...Jim Thompson
--
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