[Hammarlund] 6AH6 vs 6C4

[Carl]

You know that Ive been a proponent of bucking transformers for ages Les. There is not a piece of tube gear here that operates at over 115V and that includes many console and wood table radios scattered around in all rooms. In the basement all benches are fed with their own high current bucker that run in the 108-113V range. That alone cuts down on drift.

The 6V6 in place of the 4H4C works well and is rather impervious to momentary voltage fluctuations. National did several tests before issuing that Service Bulletin.The best test is in the Clegg Zeus where it is so stable I go down the band on 6M and ragchew with SSB stations or run them for a few hours in contests. Starting off at 125V + may not work so well. With the price of a good USA 6V6 going thru the roof I use duds that are well down in emission or have leakage.

The socket is also a good place to get spare pins when you break one doing a recap (-;


Carl
KM1H


 


----- Original Message ----- 
  From: Les Locklear 
  To: Richard Knoppow ; Carl ; kgordon2006 at frontier.com ; Hammarlund at mailman.qth.net 
  Sent: Friday, June 10, 2011 6:21 PM
  Subject: Re: [Hammarlund] 6AH6 vs 6C4


  I have my SP-600 running at 115 volts, but our local line voltage is typically 124-127. At 115 volts, the filament voltage readings are typically 6.2 volts, so they should last a lot longer.

  Les
  ----- Original Message ----- 
  From: Richard Knoppow 
  To: Les Locklear ; Carl ; kgordon2006 at frontier.com ; Hammarlund at mailman.qth.net 
  Sent: Friday, June 10, 2011 4:37 PM
  Subject: Re: [Hammarlund] 6AH6 vs 6C4



  ----- 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
   

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