[Hammarlund] 6AH6 vs 6C4

[Les Locklear]

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








----- Original Message ----- 
From: Carl 
To: kgordon2006 at frontier.com ; Hammarlund at mailman.qth.net 
Sent: Friday, June 10, 2011 12:54 PM
Subject: Re: [Hammarlund] 6AH6 vs 6C4


.
>
> Again, yes. This last is one reason that National (and others) 
> incorporated
> filament current regulation (the 4H4C in the HRO-60) in the oscillator 
> circuits.
>
> The Collins R-390 and 390A are other examples.
>
> Anyway, I am going to do some experimentation.
>
> My goals are MINIMAL circuit and mechanical changes, coupled with greatly
> enhanced stability.
>
> As I have repeatedly stated, one of my basic principles is "KISS"...
>
> BTW, Electric Radio magazine recently published a very short article on a
> solid-state plug-in replacement for the 4H4C which almost exactly mimics
> that tube's characteristics, using an LM-317 in current regulator mode.

Why not a simple HW rectifier and a zener? Seems to work for me on any free 
running oscillator of which there are 3 in the HRO-60 and NC-183D. And then, 
since VR tubes are not really stable, use some more zeners.

Id also give the 6AH6 a try as a triode for G&G, it looks pretty impressive 
that way.

Im also a firm believer in KISS and not reinventing the wheel.

Carl
KM1H





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