[Johnson] CHALLENGER STANDBY PLATE CURRENT

[Bry Carling]

That is very interesting and it.

It sounds like possibly the previous owner had melted down those two tubes and something was shorted out inside them.

Bry Carling
http://af4k.com
Sent with my iPhone 6


> On Dec 19, 2013, at 11:25 AM, Ed - K9EW <k9ew57 at gmail.com> wrote:
> 
> Just a follow-up on my problem with 80mA of plate current when in the
> STANDBY mode...
> 
> I checked C3 and C4, and they're both good.  I had already replaced C3 with
> a 450v rating capacitor.
> 
> I substituted another 6AQ5 clamp tube, but no change.
> 
> The screen grids of the 6DQ6A's in the PA were reading 0V in the STANDBY
> mode, but they were drawing 80mA of plate current.  I removed the tubes
> just to be sure I was actually measuring plate current, and without the
> tubes the current was zero.  I put the tubes back in, one at a time, and
> with one tube I got 40mA of plate current in the STANDBY mode; with both
> tubes in, I got 80mA.  Must be the tubes.
> 
> I replaced both tubes with others in my spare tube box and... that was it.
> No more plate current in the STANDBY mode.  Normal operation in the other
> switch positions.  I thought I'd ordered some new spares, but must have
> used them somewhere else.  So I'll order another pair to put in the
> Challenger.  The tubes I removed were the original Johnson-stamped tubes so
> I guess it was time for a change.
> 
> Just wanted to let others know how this was resolved in case you start
> drawing plate current in the STANDBY mode.
> 
> 73,
> ed - k9ew
> 
> 
>> On Tue, Dec 17, 2013 at 4:37 PM, Glen Zook <gzook at yahoo.com> wrote:
>> 
>> Do you have a key plugged into the key jack?  The key jack shorts the
>> cathodes to ground when there is not a key plugged in.  80 mA is not right!
>> It should be 0!
>> 
>> If you have a key plugged in, and the key is open, then there are
>> 2-capacitors that may be shorted.  The most likely is C-3, a 2 mfd
>> capacitor.  The "modern" replacement will be 2.2 mfd.  Replace with at
>> least the rated voltage on the capacitor and a higher voltage rating is
>> better.
>> 
>> The other capacitor is C-4, a .005 mfd capacitor.  The "modern"
>> replacement will be 0.0047 mfd.
>> 
>> Glen, K9STH
>> 
>> 
>> Website: http://k9sth.com
>> 
>> 
>>  On Tuesday, December 17, 2013 2:50 PM, Ed - K9EW <k9ew57 at gmail.com>
>> wrote:
>> I just got my "new" Challenger set up for my winter station, and I have a
>> question...
>> 
>> The Plate Current is about 80mA with the Operate switch in the Standby
>> position (Grid Current is zero).  Does that sound right?
>> 
>> Thanks - ed, k9ew
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