Lee -
Pin 6 'could' indicate a leaky C90A, but resistance checks through
electrolytics are so inconsistent (polarity of leads, voltage applied,
current available, etc., that I just don't bother with them.. I don't
think I have ever 'found' a problem through resistance checks!
You should have about 18 VDC across C173, with no ripple, and about 11
VDC on the other end of R130.
The output transformer isn't THAT critical, as long as it's within
reason. Easiest way to check it is to put ~2 VAC @ 1000 Hz on the
secondary and measure the voltage across the primary. On further
thought, I believe the original is a 5000 ohm primary, so if you put 2V
on the secondary, you should see about 70V on the primary. That's a
35:1 turns ratio, and with 4 ohms on the secondary the primary would be
4900 ohms. Close enough.
Perhaps Bill is 'listening' and has more accurate information??
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>
[email protected] wrote:
Garey,
Yep, I'm still up and working on this baby...
OK, one other thing I found:
Resistance checks at V7:
Pin 6 slowly goes up to 4.8K instead of being 15K like the book says
Pin 7 slowly goes up to 4.6K...pretty close to the book
I have checked a lot of resisters in both the atrea of Q7 & V7 all
look pretty good.
73,
Lee
-----Original Message-----
From: Garey Barrell <[email protected]>
To: drakelist <[email protected]>
Sent: Fri, Apr 1, 2011 9:36 pm
Subject: Re: [Drakelist] Fwd: My R-4B audio?
Lee -
The output transformer is a 2500 to 4 ohm. Probably any small, single
tube output transformer will work. The primary current is about 40 mA.
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>
[email protected] wrote:
BIG UPDATE,
I just discovered someone has changed the audio output XFMR!
I can tell because they left a small piece of the original secondary
wire on the phone jack terminal wher it connects...it is the cloth
covered wire.
Hmmmm.
who know what it is, if it is correct.......
Wander if I can find one???
Anyone have one I can buy?
That may not even be the issue...if I knwe what the input signal level
was supposed to be that would help.
73,
Lee
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