[ARC5] REAL regen receivers RAL/RAK.

[Roy Morgan]

On Jun 7, 2010, at 11:59 PM, Kenneth G. Gordon wrote:
>
> I do. I have several now, one in operation, the others on  
> "standby"....it is a really superb receiver.

Ken,

  Have I sent you my notes file on these?  It includes the  
modifications suggested by a fellow in Mass who's puzzled over them  
for quite some time.

These changes result in a smoothly operating receiver, the way it should
have been in 1936.
Richard Brunner, AA1P   18 Juli 2003

Detector:
1.  Change C112, 510 µµfd grid capacitor to approx. 100 µµfd.
2.  Change C120, C121,  51µµfd decoupling capacitors to 600-1000 µµfd.
These changes change signals from raspy to pure dc, and keep rf out of  
the
audio amplifier.

Audio Amplifier:
1.  Disconnect C124, .001 µfd and C133, .01 µfd plate to ground bypass
capacitors.
2.  Add shielding to all low-level audio leads to the extent  
possible.  Most
come out of the low-    pass filter.  Strip braid from old RG-58  
coax.  Lift
one end of the audio leads and slip braid over them.  Ground one end  
only of
the braid.
3.  Add a tube shield to the 41 audio output tube.
The 5 or 6 feet of unshielded wiring caused a supersonic oscillation (33
volts at the 'phones) and the developers added C124 and C133 to limit
frequency response enough to kill the oscillation.  This is why Broad  
and
Sharp aren't much different.  There is enough capacitance from the 41  
plate
to adjacent wiring for oscillation. (17 volts on the 'phones)
4.  Add approx 4.4 Meg resistor from one side of the output  
transformer (the
side that doesn't oscillate) to the 6D6 grid.  Inverse feedback reduces
ambient noise and improves linearity.
5.  Add capacitance to the 6D6 and 41 cathode bypasses.
6.  Pull back the dc power switch and tape/insulate it.  Install an OC  
phone
jack shunted with a 1 Meg resistor.  Connect jack with a .01 µfd  
capacitor
to the 41 plate.  This gives hi-Z output.  The resistor is to  
eliminate a
big click and charging current when the 'phones are plugged in.

Addendum:
Change R121, 1 Megohm 41 grid resistor to 470 k Ohms.
RCA receiving tube manual recommendation.


Roy

Roy Morgan
k1lky at earthlink.net
529 Cobb St.
Groton NY, 13073
Home: 607-898-3607
Cell: 301-928-7794