[Johnson] valiant audio problems

[Larry Knapp]

Ronnie - Interesting question....not sure how many replies you have had, but
when you do find the answer, could you please share it.

My first thought is are you sure the D104 is wired correctly for the Valiant? 
I know you say the D104 works on your Ranger, but are the two mic pins wired
the same?

Second, you can change mic heads on the Astatic mics very easily; I am assuming
here that you are using the original TU stand.  Seeing that the stand is wired
for the 10DA you should be able to take that head off and put the D104 mic head
on that same stand and see if it works.  If not then, I wouls suspect a
cartridge.  The D104 should have more than enough to punch the audio on your
Valiant...does on mine and many others I have talked to.

Gary, K4FMX, could possibility be correct also...He wrote "I had the exact same
problem with a heathkit ssb transmitter one time. I bought 3 new D104
cartridges before I figured out the problem. The first audio stage had a leaky
grid. With a dynamic mike hooked to it it worked fine as the coil in the mike
shorted the grid to ground so the voltage could not creep up. But with the D104
there was only the grid resistor and the grid voltage would go up an bias the
tube wrong.

Check the first audio tube again and check that the grid resistor is good."...

I double check changing heads, then of you have any other known good mic heads
I'd interchange just to be sure...in any event, share with the group when you
find the problem.

73 & good luck, Larry KC8JX


--- w5sum@glowbugs.com wrote:
> howdy men
> This will be somewhat long. Put on your thinking caps :)
> 
> My valiant has some quirky problems with the audio. I can use an 
> astatic 10DA and I get PLENTY of audio. In fact I only have to turn 
> the gain up to about the 10 or 11 o'clock position to get all the 
> audio I need. BUT when I use the D104 I have to turn the audio gain 
> up nearly all the way and it sounds like poop.
> 
 Somewhere 
> along this path, it had its microphone chassis connector changed 
> out to a CB type 4 pin plug.  When examining it, it looked like it 
> had been wired up by a drunk monkey with a blow torch! I found a
> PAIR of cermet 474K resistors in parallel, in place of the 1 Meg 
> Resistor that was supposed to be there ( grid input of first audio 
> stage)   This pair of resistors in parallel were reading real squirrely
> with my DVM and in fact, ranged up and down from 5 Meg ohm to
> 25 megohm!!!  Anyway, put a nice Allen Bradley 1M 1% in there
> and put in a regular two pin mic connector that was supposed to be
> there. I also changed out the two .005's and the 300pf caps that
> are hooked to the mic connector ( the 300 was hooked to pin 2 of
> first audio)
> 
> On the air tests this morning got me an A+ for audio when using 
> the 10DA but the D104 still has to have way too much audio gain
> to 100% modulate and still sounds like crap.  This D104 is used 
> daily with a Ranger and gets glowing reports so I know its good.
> 
> I have changed out the 12AX7, and the 6C4 in the audio, as well
> as the 12AU7 ( the clipper circuit is bypassed)
> 
> So, I can't imagine why a D104 would not have enough drive for this 
> rig, or WHY it sounds so darned bad.
> 
> any suggestions?
> 
> thanks in advance
> 
> Ronnie



=====
May your days be full of sunshine and good thoughts fill your head.
From: Larry Knapp, KC8JX, St. Joseph, Mi  49085
  Best 73's

__________________________________________________
Do You Yahoo!?
Send FREE Valentine eCards with Yahoo! Greetings!
http://greetings.yahoo.com