[AMRadio] Ranger Audio... the Pics


Rick Brashear rickbras at airmail.net
Sat Nov 18 23:54:44 EST 2006


Jack,

I have a simple method I use when things get to this point.  With the 
scope attached to the output of each stage I inject an audio signal into 
that stage.  Usually, I start at the speaker end in a audio amplifier 
which is all a modulator is.  So, if you were to place your scope at the 
output of the modulation transformer and a known pure audio signal at 
center tap of T3's secondary you could see if the 6L6's and T2 (and 
their associated circuitry) are causing the trouble.  If not, back up to 
the grid of V8 with the audio signal.  If that's okay, back up to the 
center tap of the volume control.  I use a signal tracer in conjunction 
with my oscilloscope so I can hear as well as see what's going on.  This 
is a guaranteed method of isolating the problem.  No need to search the 
entire audio/modulation circuitry if you can isolate it to a specific 
area.  This works well for me in almost all of my troubleshooting endeavors.

Rick


Jack Schmidling wrote:

> k0ng at inebraska.com wrote:
>
>
>> Just my opinion. I have not been following the problem. What are you  
>> looking for??
>
>
> Well, the current problem is the fact everyone complains about my 
> audio.    Tinny, yucky, narrow... like an old telephone, etc.
>
> New (used) D104 is the worst of the bunch but known good mics that I 
> have used for years, doing voice overs for film and video don't sound 
> much better.
>
> I taped tests of 3 of them and the D104 sounds lousy and the dynamic 
> and electret lapel sound just fine and are nearly indistinguishable 
> from each other.
>
> When I put them under an earphone tuned to a good broadcast signal and 
> fire the Ranger into a dummy or antenna, they all sound lousy.
>
> Seems obvious the Ranger is doing something to the audio so I have 
> been sig tracing to see where and the pics are what I found.
>
> In the meantime, I removed caps one at a time from the front end and 
> none of them made the slightest difference.  I left them all out and 
> decided it's time for a break.
>
> I have no idea where to go from here.
>
> js
>




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