Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Andy -
Well you can try whatever you have handy (50-60 uF or more at 250VDC or
more) across C129 just to check. Good Twist-Lok electrolytics are just
about impossible to find, so if you have to replace it, I would suggest
just cutting the terminal off the bottom of the can and wiring in a
tubular cap under the chassis. Do NOT leave the old cap connected if it
is bad. Lead length is NOT critical (within reason), so you can put the
new cap wherever it will fit.
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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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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