Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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All except R65 and C80 are related to AVC attack and decay times. Drake
didn't change them because they got a "buy" on surplus parts! :-)
None of them are difficult to do, and there are no hard to get parts
involved, with the exception of the switch. Personally, I hardly ever
use Fast AVC. I suppose it would allow faster response to fading AM
signals, and might be necessary for full break-in CW, but other than that...
That said, if you can't find a dpdt switch with a red handle, I would
replace R47 with a 33k resistor, (or 31.5k equivalent to the combination
of R47 and R71 in Slow AVC,) and go. It's possible that this would
result in "thumping" or other unwanted effect on Fast AVC, but perhaps
not. If it did, you could begin raising the value for the best
"compromise".
73, Garey - K4OAH
Glen Allen, VA
Darrell Bellerive wrote:
Garey has confirmed that the schematic that came with my 2-B manual is the
proper manual that came with the 2-B from the factory.
My schematic is numbered 124614500.
Comp. MySchematic s/n 5735 Late Version
C34 0.005uF 0.005uF 0.005uF
C63 0.0024uF 0.0024uF 0.001uF
C67 0.01uF 0.01uF 0.001uF
C80 N/A N/A 0.02uF
R47 68k 68k 680k
R65 1.5k 1/2w 1.5k 1w 1.5k 1w
R71 N/A N/A 33k
So now the question becomes, is it worth updating my 2-B to match the latest
version from Drake?
I would have to change C63, C67, R47, and add R71, C80 and replace the AVC
switch with a double pole version.
Looks like C67 and R47 are part of a timing circuit in the AVC. Both
components have been shifted an order of magnitude from the early 2-B to the
late 2-B.
C63 is also part of the AVC. I'm not certain as to what it's function is, but
I suspect changing it will alter the frequencies that influence the AVC
action.
Garey already stated that C80 is an additional filter on the Bias supply, and
R71 decreases the IF AVC attack time in Slow AVC.
Looks like someone already changed R65 to a 1 watt.
Should I make the changes or not?
73, Darrell VA7TO
On Thursday 24 July 2008 09:26, Garey Barrell wrote:
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist
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Darrell -
There are a few changes between the two versions.
Comp. s/n 3001 s/n 6290 Loc.
C34 N/A 0.005 uF V2
C63 0.0024 uF 0.001 V6
C67 0.01 0.001 V8
C80 N/A 0.02 V8
R47 68k 680k V8
R65 1.5k 1/2W 1.5k 1w V2
73, Garey - K4OAH
Glen Allen, VA
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