"Andrew Catanzaro" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Garey,
Thanks very much for the advice. I had seen there was a replacement supply
available, but I didn't know if this would take care of this specific
problem. I needed a push to get it. If it doesn't fix the burble, I'll let
you know. I guess I have to come up with my own C129 on my own.
73,
Andy W9NJY
----- Original Message -----
From: "Garey Barrell" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Sunday, July 29, 2007 11:43 AM
Subject: Re: [drakelist] Fine burble on T-4XB note
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist
gang
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Andy -
Most likely power supply ripple. There are not many good caps left in
AC-3s after almost 50 years.
Since you are able to replicate the burble locally, you could try bridging
a good cap across the can cap in the T-4XB itself (C129), and the output
cap (C5b) of the bias supply in the AC-3 (watch polarity!). Those are
the two most likely troublemakers. If neither of those affect the burble,
you could try to bridge the output cap of the LV supply (C4b).
If bridging the caps in the AC-3 resolves the problem, you might want to
consider the AC-4R from The Heathkit Shop. It replaces everything except
the transformer and bias pot.
73, Garey - K4OAH
Glen Allen, VA
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Andrew Catanzaro wrote:
"Andrew Catanzaro" <[EMAIL PROTECTED]> made an utterance to the drakelist
gang
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I have recently gotten a Drake B-line operational and am very happy with
it. The R-4B is a fantastic receiver. I have built two Norcal DDS VFO's
to replace the PTO's and it's great having frequency resolution to the
last Hz and no drift.
A friend with good ears and who lives close by told me that there is an
irregularity on my CW note. People far away tell me my note is fine. I
took a separate receiver and used only a dummy load on the transmitter
and a dummy load on the receiver so it would not be overloaded. I can
hear the raspiness or burble. It's like a fine modulation on an
otherwise great CW note. Going back to the original Drake PTO does not
fix the problem. It sounds exactly the same. I swapped out all the
tubes for NOS, and there was no change. I am using an AC-3 power supply
with the original caps. There is nothing that sounds like AC hum on the
signal. Is this a normal observation of the T-4XB's CW note or is there
something wrong? Except for my friend four miles away, and my own
observations, all comments on the Drake's signal have been unqualified
positive remarks.
I listen to my K2's CW note in the same test receiver with the same dummy
loads and the K2's note is absolutely pure.
Any comments or suggestions greatly appreciated!
73,
Andy W9NJY
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