[Hammarlund] 6AH6 vs 6C4

[Richard Knoppow]

----- Original Message ----- 
From: "Les Locklear" <leslocklear at cableone.net>
To: "Carl" <km1h at jeremy.mv.com>; <kgordon2006 at frontier.com>; 
<Hammarlund at mailman.qth.net>
Sent: Friday, June 10, 2011 11:52 AM
Subject: Re: [Hammarlund] 6AH6 vs 6C4


> Also, remember this National said an acceptable sub for 
> the 4H4C was a 6V6. So much for voltage regulation.
>
> Or, do what John R. Leary did on many of his custom 
> SP-600's, use two voltage regulators, an OA2 which is used 
> in all SP-600's and added a OB2 for the screen voltage as 
> the OA2 was already running at it's limits.
>
> I have a blacked faced Leary SP-600 with a product 
> detector that works spectacularly, very stable, more so 
> than most Drake R7/R7A's I've owned or operated. I don't 
> see the big "problem" with the 6C4, yeah some Hammarlunds 
> are fussy about which one you use, but for the most part, 
> it isn't that big a deal.
>
> An HQ-110 has many more disadvantages than the oscillator 
> imho. YMMV
>
> Les Locklear
> Gulfport, Ms.
> DX'ing Since '57
>
    Acceptable might mean only that the unit will work. I 
know that some receivers, for instance the SP-600-JX, with 
which I know you are very familiar, drifts a lot with 
variation in line voltage. Since the plate voltage of the LO 
is controlled by a regulator tube its the filament voltage 
causing the problem. Further, it has the slow characteristic 
of a filament changing temperature. The idea of the Amperite 
regulator is that it uses an iron wire with the opposite 
temperature co-efficient of tungsten, the result being 
constant current drop through the regulated tube. A 6V6 may 
have the right overall voltage drop for the regulated 
filament to operate at the right voltage but it will not 
compensate for variation. I think this should be easy to 
test if you have a receiver which uses a ballast tube. 
Simply put the thing on a variac and see how much frequency 
change you get over a range of line voltages (say 105V to 
125V) with the ballast and with the 6V6. My guess is that 
the drift will be there when the substitute is in place. I 
_don't_ have such a receiver so can't make the test.
     I have serious line voltage variation here due to old 
wiring and maybe just being in the big city. I run my SP-600 
on a Sola transformer which makes it perfectly stable.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com