Hi All,

I picked up a D104 Silver Eagle and was observing the output of my
scope.

I see that it appears to clip out the negative peaks which makes the on
the air sound distorted. I checked the audio with the output
terminated into 100K and also tried various settings and battery
voltage levels.

Any thoughts?

de KJ4UO

Just a guess -- but maybe an impedance matching problem
See URL:
http://www.kb2ljj.com/data/mic/D-104.htm

--
CL -- I doubt, therefore I might be !






wrote in message
ups.com...
Hi All,

I picked up a D104 Silver Eagle and was observing the output of my
scope.

I see that it appears to clip out the negative peaks which makes the on
the air sound distorted. I checked the audio with the output
terminated into 100K and also tried various settings and battery
voltage levels.

Any thoughts?

de KJ4UO

Another thought - the Silver Eagle is an amplified D-104.
Bypass the amp and see what you get.
A friend had a bad amp in the base of the D-104

--
CL -- I doubt, therefore I might be !






"Caveat Lector" wrote in message
news:TCUVf.14386$6a1.5913@fed1read04...
Just a guess -- but maybe an impedance matching problem
See URL:
http://www.kb2ljj.com/data/mic/D-104.htm

--
CL -- I doubt, therefore I might be !






wrote in message
ups.com...
Hi All,

I picked up a D104 Silver Eagle and was observing the output of my
scope.

I see that it appears to clip out the negative peaks which makes the on
the air sound distorted. I checked the audio with the output
terminated into 100K and also tried various settings and battery
voltage levels.

Any thoughts?

de KJ4UO

Caveat Lector wrote:

Another thought - the Silver Eagle is an amplified D-104.
Bypass the amp and see what you get.
A friend had a bad amp in the base of the D-104

They're also prone to be affected by rf. I had a coiled cord on mine
and had to run a direct wire inside the cord from the base to the mic
plug to get rid of the rf.

-Bill

OK. Have you checked with varying the settings of the 5k pot in the amp
section? - have you checked that the battery volatge is correct (ie,
measured it?). If that doesnt work, connect your CRO across the mic.
capsule and see if its the cause of the problem..... If its the amp,
shouldnt be too hard to troubleshoot - even if you shotgun replace
EVERY component on the board its a simple job. For schematic, just
Google for it - for some reason, I cant copy the link to this reply.

Andrew VK3BFA.

Good advice -- here is a D104 Schematic - Doesn't say Silver Eagle but think
it applies

http://www.astatic.com/cb/pdf/d104_schematic.pdf

Or

http://www.ronharter.com/documents/d104_schematic.pdf

--
CL -- I doubt, therefore I might be !






"Andrew VK3BFA" wrote in message
oups.com...
OK. Have you checked with varying the settings of the 5k pot in the amp
section? - have you checked that the battery volatge is correct (ie,
measured it?). If that doesnt work, connect your CRO across the mic.
capsule and see if its the cause of the problem..... If its the amp,
shouldnt be too hard to troubleshoot - even if you shotgun replace
EVERY component on the board its a simple job. For schematic, just
Google for it - for some reason, I cant copy the link to this reply.

Andrew VK3BFA.

Maybe one of the transistor's biasing network is at fault. I'll assume
the transistors are biased class A, which means the collector voltage
(assuming common emitter circuit) should be at about 1/2 of the supply
voltage. It sounds like one of them might have the collector voltage
running below 1/2 of Vcc. Check the resistor values with an ohmmeter.
Transistors are usually the last thing to replace...

Scott
N0EDV

wrote:
Thanks for the Schematic link.

The D104 is connected to the Oscope and terminated into a 100K
resistor. It is not connected to the radio so RF is out.

The Oscope shows clipping on the negative peaks, the postive peaks are
OK.

I tried removing the battery and powering off a power supply where I
could vary the voltage to see if the distortion disappeared with
voltage, it did not. The affect was a lower audio output.

the best thing to do is to replace the two NPN and see what happens.

de KJ4UO

On 28 Mar 2006 20:10:08 -0800, wrote:


Thanks for the Schematic link.

The D104 is connected to the Oscope and terminated into a 100K
resistor. It is not connected to the radio so RF is out.

The Oscope shows clipping on the negative peaks, the postive peaks are
OK.

I tried removing the battery and powering off a power supply where I
could vary the voltage to see if the distortion disappeared with
voltage, it did not. The affect was a lower audio output.

the best thing to do is to replace the two NPN and see what happens.

de KJ4UO


First bypass the amp and see what it does. It may be a bad element.
They will sometimes give funny distortion when they go bad.

73
Gary K4FMX

In article , Scott
wrote:

Maybe one of the transistor's biasing network is at fault. I'll assume
the transistors are biased class A, which means the collector voltage
(assuming common emitter circuit) should be at about 1/2 of the supply
voltage. It sounds like one of them might have the collector voltage
running below 1/2 of Vcc. Check the resistor values with an ohmmeter.
Transistors are usually the last thing to replace...

Scott & PD-

I agree that the transistors are most likely good.

If this microphone had a former life connected to a CB set, it may have
always had the problem. Resistors would have to drift a long way to cause
the problem, but what if one of them was the wrong value to begin with?
Perhaps off by a factor of ten?

Leakage in the 0.1 capacitor is the next likely suspect.

The diagram I downloaded doesn't have a value for one of the resistors. I
would guess its value might be between 500K and 1Meg Ohm at the input to
the first transistor.

Fred

wrote:
The D104 is connected to the Oscope and terminated into a 100K
resistor. It is not connected to the radio so RF is out.

Wasn't the amplified version supposed to be low impedance?
http://www.kb2ljj.com/data/mic/D-104.htm shows a Silver Eagle
"Final Edition" and says "Impedance: 500 ohms max."

I do see stuff on the web that suggests that the high impedance
versions wanted no less than 1 megohm load, one saying that 10 meg
was nearly ideal.

--
All relevant people are pertinent.
All rude people are impertinent.
Therefore, no rude people are relevant.
-- Solomon W. Golomb