[Drakelist] R-4A Notch trouble

2010-01-15 Thread Karl Henrik Laache
Hi

My R-4A project is puzzling
me.  It sounds ok, but when I
go through the adjustment
procedure I'm puzzled.  The
book says thet the tuning of
T7 andT10 is quite broad.  For
sure, I can't get a maximum at
all.  And the notch will not
work.  There is absolutely no
response to any setting of the
notch controls.  I have tried
to replace the tubes with
known good ones - no
difference.  I have measured
the notch coil, seems good
(only ohms resistance).  I
have not tried to adjust the
core of the notch control for
fear of doing something wrong.
It would be very strange if it
should be out of tune.  

 

Where should I start?

 

73s de Karl LA1CU

la...@nrrl.no 

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Re: [Drakelist] R-4A Notch trouble

2010-01-15 Thread Garey Barrell

Karl -

Three things. One, the IF must be aligned properly, i.e., on frequency. 
Two, NOTCH is VERY narrow. It's easy to go right past it if you turn the 
knob too fast. Three, the NOTCH ADJUST control on the right side of the 
chassis must be adjusted as well. These two must be adjusted alternately 
for the best notch.


73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line  TR-4/C Service Supplement CDs
www.k4oah.com


Karl Henrik Laache wrote:


Hi

My R-4A project is puzzling me. It sounds ok, but when I go through 
the adjustment procedure I’m puzzled. The book says thet the tuning of 
T7 andT10 is quite broad. For sure, I can’t get a maximum at all. And 
the notch will not work. There is absolutely no response to any 
setting of the notch controls. I have tried to replace the tubes with 
known good ones – no difference. I have measured the notch coil, seems 
good (only ohms resistance). I have not tried to adjust the core of 
the notch control for fear of doing something wrong. It would be very 
strange if it should be out of tune.


Where should I start?

73s de Karl LA1CU

la...@nrrl.no





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