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Gentlemen:
Just a reminder that Donnie Garrett has a simple
and effective cure for the bad can cap on the R4/A/B. Check out his web
site at WA9TGT for that and other great ideas for making your Drakes look and
work better.
I have no comercial connection - just a very
happy, and frequent, customer.
73
Peter
VE3AX
----- Original Message -----
Sent: Wednesday, November 23, 2005 12:10
AM
Subject: Re: [drakelist] R-4B T-4XB
question
Hi Jason,
I left the can in place and just disconnected
it. Fresh radial caps were mounted on a small homemade PCB underneath
the chassis. You need to use small modern caps in order for the board to
fit. While I was in there, I went ahead and replaced the other
electrolytics under the chassis (as a preventive) even though none of them
were showing any signs of trouble. I consider replacing the big can the
only must-do if you're experiencing hum problems. The other
electrolytics are exposed to less stress.
Denny AE6C
On 11/22/05, Jason
Buchanan <[EMAIL PROTECTED]>
wrote:
Dennis
Monticelli wrote:
> Hi Jason,
>
> I also noted that CW
notes were hum modulated in my R4B. Because you
> remember
better performance in the past, perhaps the big can is going
> south
on you? I have only worked on two Drakes (a 4A and a 4B) and
> both of them needed can replacement. Post replacement,
both radios
> still had finite residual hum, though much improved from
before. My
> R4B is no longer modulating CW
notes. After a doubling of the
> capacitance of the first
filter section, the hum is now inaudible.
>
> See my earlier
post regarding the 4B and Garey's suggestions for
> alleviating
headphone hum.
>
> Look for a bulge in the PS can or a hotter
than normal can or
> excessive ripple on the filter
sections. The first filter section
> (across the raw DC) is
hammered by the most ripple current and can be
> expected to fail
first due to localized heat buildup. If the measured
>
voltage ripple is much more than about 8Vpp, it should be replaced.
>
While you're in there, I would replace the other (less stressed)
>
sections at the same time.
>
> Denny AE6C
hi - thanks
for the advice. Can you point me in the right direction of
the
components I should replace? The big can near the transformer is
an
obvious one (although i'm afraid it won't be replaced with one that is
so pretty looking - these new can electrolytics are black and ugly
hi)
but I don't know what others I should target. I can solder
well, just
not sure what other places will need to be retooled inside the
R4B.
Same for the T-4XB but I think i'll take care of the biggest
problem
areas with the AC-4
rebuild.
Thanks,
Jason
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- Re: [drakelist] R-4B T-4XB question VE3AX
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