HELP: KWM-2 Motoroboating on Rx Audio
 

Hello Collins KWM-2 users:

I've almost got my KWM-2 working again, but noticed a problem that is
eluding me.
The Radio receives "great" with RF Gain turned up, BUT when the Audio
Gain Control is increased the RX audio
starts to Motoroboat , which overrides the incoming audio.
The motoroboating occurs even when the RF gain is turned down and the audio
control is increased.

I suspect this is NOT normal, but have never had a KWM-2 previously.

Can anyone advise if this is "normal"? OR if "not"...has anyone had this
experience and can offer any advise as to
a possiable solution.

Thank You....Norm VE3CZI

HELP: KWM-2 Motoroboating on Rx Audio
 

Norm VE3CZI wrote:
Hello Collins KWM-2 users:

I've almost got my KWM-2 working again, but noticed a problem that is
eluding me.
The Radio receives "great" with RF Gain turned up, BUT when the Audio
Gain Control is increased the RX audio
starts to Motoroboat , which overrides the incoming audio.
The motoroboating occurs even when the RF gain is turned down and the audio
control is increased.

I suspect this is NOT normal, but have never had a KWM-2 previously.

Can anyone advise if this is "normal"?

You need even ask? Art Collins is rolling over in his grave.

OR if "not"...has anyone had this
experience and can offer any advise as to
a possiable solution.

Motorboating is a low frequency oscillation that is caused by varying
current draw in the audio output stage causing the power supply voltage
to rise and fall and get fed back into the input stages. You have a
bad coupling capacitor, or a bad electrolytic in the power supply.

Check C106A and C.

-Chuck

HELP: KWM-2 Motoroboating on Rx Audio
 

On Mar 7, 2:00 pm, "Norm VE3CZI" wrote:
Hello Collins KWM-2 users:

I've almost got my KWM-2 working again, but noticed a problem that is
eluding me.
The Radio receives "great" with RF Gain turned up, BUT when the Audio
Gain Control is increased the RX audio
starts to Motoroboat , which overrides the incoming audio.
The motoroboating occurs even when the RF gain is turned down and the audio
control is increased.

I suspect this is NOT normal, but have never had a KWM-2 previously.

Can anyone advise if this is "normal"? OR if "not"...has anyone had this
experience and can offer any advise as to
a possiable solution.

Thank You....Norm VE3CZI

Does adjusting the VOX gain have any effect?

HELP: KWM-2 Motoroboating on Rx Audio
 

Norm VE3CZI wrote:
Gain Control is increased the RX audio
starts to Motoroboat , which overrides the incoming audio.
The motoroboating occurs even when the RF gain is turned down and the audio
control is increased.

I suspect this is NOT normal, but have never had a KWM-2 previously.

It is very much not normal. You have a filter cap somewhere in the audio
section, most likely somewhere in the power amplifier section. While you
are in there, I believe there are some cathode bypass caps that ought to
be changed out too.

Can anyone advise if this is "normal"? OR if "not"...has anyone had this
experience and can offer any advise as to
a possiable solution.

Motorboating is a low-frequency oscillation usually caused by the power
supply not being stiff enough; a high level signal pulls the B+ down,
which reduces the gain which reduces the load so the B+ goes back up
again... and on and on.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

KWM-2 Motoroboating on Rx Audio
 

Tnx to all who took the time to voice thier thoughts. I think C106 is the
centre of attention at this time. Guess will have to bite the bullet and
replace the C106 Electrolytic
73...Norm VE3CZI

"Norm VE3CZI" wrote in message
...
Hello Collins KWM-2 users:

I've almost got my KWM-2 working again, but noticed a problem that is
eluding me.
The Radio receives "great" with RF Gain turned up, BUT when the Audio
Gain Control is increased the RX audio
starts to Motoroboat , which overrides the incoming audio.
The motoroboating occurs even when the RF gain is turned down and the
audio control is increased.

I suspect this is NOT normal, but have never had a KWM-2 previously.

Can anyone advise if this is "normal"? OR if "not"...has anyone had this
experience and can offer any advise as to
a possiable solution.

Thank You....Norm VE3CZI