Garey,
Diode D3 appears to be good..and I checked D1 & D2 while I was at it.
Diode D3:
V10b Cathode side 4.5 volts. And it varies in voltage a lot based on.
NB is off.
SSB signals being rcvd. pulses up a lot with static crashes.
The non-cathode side of D3 is 150 vlots if NB is OFF and 30 volts if
it is
on...no variance with signals rcvd.
OK, this AM I discovered with the scope what I think is going on....
If you tune in ...say a nice 20 over 9 signal on say 40m LSB. Thr RX
sounds very nice indeed (Assuming no other strong signal is nearby)
THEN...if you either tune to the other sideband OR just move the PB
tuner to USB....lots of noisey, clicking sounds appear when he
modulates.
OK, now with the scope...you can see this on the cathode of V10B.
Remember NB is OFF. (When on the problem stillhappens, just the pulses
look a little better)
Now, I looked on the plate of V9 The NB IF amp...WOW...with things
normal on LSB good sounding signal I see...around 5-10 volts P-P od SSB
signal shape..then when I tune to USB or just move the dial to the
opposite side of the sugnal...
I Get 60 -100 Volts P-P od signal and that is I beleive triggering the
NB. The PB tuner is a stage after this so it is a little confusing what
is hapening.
If during this failure mode I pull V9 or V10 All is quiet and the RX
works fine.
Would really appreciate an idea or two as this is,,,, well quite a
challange (and it will be fun to fix this)
Thanks,
73,
Lee
Lee Simmonds
Summit DCS LLC
260-799-4077 Office
260-403-6936 Cell
-----Original Message-----
From: Garey Barrell <k4...@mindspring.com>
To: kc9cdt <kc9...@aol.com>
Cc: drakelist <drakelist@zerobeat.net>
Sent: Tue, Jan 10, 2012 11:01 am
Subject: Re: [Drakelist] R-4A, NB issues
Lee -
Check D3 for leakage.
Clean switch contact on S3(f)
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>
kc9...@aol.com wrote:
Hi gang,
DX sure has been fun lately!
Been working on a R-4A, 11 tube version....it's really sounding
good...fixed several problems and did a complete alignment.
In thourough testing I discovered a problem...seems the NB is causing
clicking or pulse noise on normal signals.
That is with it OFF or ON.
I can tune through signals and at certain points , depending on the
adjacent signals etc I hear the clicking or popping noise during the
modulation of the signals.
And if I tune in a single signal, a good loud one , then turn the PB
tuning to the opposite SB, I can hear the clicking/popping.
IF I PULL the NB AMP V10, The problem goes away!
So, either the NB is on all the time (even with the sw. off) OR there
is a problem in the NB circuit I'll have to find...
Before I did in deeper....anyone have any ideas on what the problem
is??
Thanks,
73,
Lee, KC9CDT
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