After my Ranger is on for a short period of time, I am noticing that
the final plate current starts creeping up slowly and will continue to
climb if I do not power off the transmitter. I have the PTT mod in
there where it grounds the screen through the 5K resistor. It does
this in any mode position until I switch off the power. I believe that
the 6146 maybe self oscillating? I do notice that the screen voltage
(pin 3) increases along with the plate current even though it is
grounded through the 5K resistor. Possibly it needs neutralizing or I
have a bad 6146? Any ideas will be most appreciated. 73, Randy, WB5KCM

On Mar 19, 1:59 pm, "wb5kcm" wrote:
After my Ranger is on for a short period of time, I am noticing that
the final plate current starts creeping up slowly and will continue to
climb if I do not power off the transmitter. I have the PTT mod in
there where it grounds the screen through the 5K resistor. It does
this in any mode position until I switch off the power. I believe that
the 6146 maybe self oscillating? I do notice that the screen voltage
(pin 3) increases along with the plate current even though it is
grounded through the 5K resistor. Possibly it needs neutralizing or I
have a bad 6146? Any ideas will be most appreciated. 73, Randy, WB5KCM

I have found some info about the Ranger having rivited tube sockets
not making a good chassis ground connection. This can cause symptoms
like I am having. It seems the problem only occurs after the 6146 gets
heated up well. There is some possibility that the clamper tube (6AQ5)
may cause this also if it is not functioning correctly. I notice that
when this starts, I can put the VFO/Crystal switch in the "Zero"
position and the final current will drop to a low level. Any other
position it will continue to climb until I turn off the power.

Hi,

In addition to changing out the 6AQ5 clamp tube,
I would check the value of the 11 K resistor
(3 parallel 33K resistors)
at the 6AQ5 screen - mine had changed value to only 6.8K.

I replaced them with three 2W metal film resistors.

73,
Ed Knobloch

wb5kcm wrote:
On Mar 19, 1:59 pm, "wb5kcm" wrote:
After my Ranger is on for a short period of time, I am noticing that
the final plate current starts creeping up slowly and will continue to
climb if I do not power off the transmitter. I have the PTT mod in
there where it grounds the screen through the 5K resistor. It does
this in any mode position until I switch off the power. I believe that
the 6146 maybe self oscillating? I do notice that the screen voltage
(pin 3) increases along with the plate current even though it is
grounded through the 5K resistor. Possibly it needs neutralizing or I
have a bad 6146? Any ideas will be most appreciated. 73, Randy, WB5KCM

I have found some info about the Ranger having rivited tube sockets
not making a good chassis ground connection. This can cause symptoms
like I am having. It seems the problem only occurs after the 6146 gets
heated up well. There is some possibility that the clamper tube (6AQ5)
may cause this also if it is not functioning correctly. I notice that
when this starts, I can put the VFO/Crystal switch in the "Zero"
position and the final current will drop to a low level. Any other
position it will continue to climb until I turn off the power.

On Mar 21, 11:40 am, Edward Knobloch wrote:
Hi,

In addition to changing out the 6AQ5 clamp tube,
I would check the value of the 11 K resistor
(3 parallel 33K resistors)
at the 6AQ5 screen - mine had changed value to only 6.8K.

I replaced them with three 2W metal film resistors.

73,
Ed Knobloch



wb5kcm wrote:
On Mar 19, 1:59 pm, "wb5kcm" wrote:
After my Ranger is on for a short period of time, I am noticing that
the final plate current starts creeping up slowly and will continue to
climb if I do not power off the transmitter. I have the PTT mod in
there where it grounds the screen through the 5K resistor. It does
this in any mode position until I switch off the power. I believe that
the 6146 maybe self oscillating? I do notice that the screen voltage
(pin 3) increases along with the plate current even though it is
grounded through the 5K resistor. Possibly it needs neutralizing or I
have a bad 6146? Any ideas will be most appreciated. 73, Randy, WB5KCM

I have found some info about the Ranger having rivited tube sockets
not making a good chassis ground connection. This can cause symptoms
like I am having. It seems the problem only occurs after the 6146 gets
heated up well. There is some possibility that the clamper tube (6AQ5)
may cause this also if it is not functioning correctly. I notice that
when this starts, I can put the VFO/Crystal switch in the "Zero"
position and the final current will drop to a low level. Any other
position it will continue to climb until I turn off the power.- Hide quoted text -

- Show quoted text -

Thanks Ed, I will check this today.

On Mar 21, 5:05 pm, "wb5kcm" wrote:
On Mar 21, 11:40 am, Edward Knobloch wrote:





Hi,

In addition to changing out the 6AQ5 clamp tube,
I would check the value of the 11 K resistor
(3 parallel 33K resistors)
at the 6AQ5 screen - mine had changed value to only 6.8K.

I replaced them with three 2W metal film resistors.

73,
Ed Knobloch

wb5kcm wrote:
On Mar 19, 1:59 pm, "wb5kcm" wrote:
After my Ranger is on for a short period of time, I am noticing that
the final plate current starts creeping up slowly and will continue to
climb if I do not power off the transmitter. I have the PTT mod in
there where it grounds the screen through the 5K resistor. It does
this in any mode position until I switch off the power. I believe that
the 6146 maybe self oscillating? I do notice that the screen voltage
(pin 3) increases along with the plate current even though it is
grounded through the 5K resistor. Possibly it needs neutralizing or I
have a bad 6146? Any ideas will be most appreciated. 73, Randy, WB5KCM

I have found some info about the Ranger having rivited tube sockets
not making a good chassis ground connection. This can cause symptoms
like I am having. It seems the problem only occurs after the 6146 gets
heated up well. There is some possibility that the clamper tube (6AQ5)
may cause this also if it is not functioning correctly. I notice that
when this starts, I can put the VFO/Crystal switch in the "Zero"
position and the final current will drop to a low level. Any other
position it will continue to climb until I turn off the power.- Hide quoted text -

- Show quoted text -

Thanks Ed, I will check this today.- Hide quoted text -

- Show quoted text -

OK, I found a NOS RCA JAN 6146 this morning at the Weatherford
Hamfest. Put it in and its working fine now. The 6146 was bad or the
Ranger sure didnt like that 6146B model in there. Got it all going
now. Thanks to all for the suggestions.
73 de Randy, WB5KCM