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Replace 1L6 with DK92

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Forum » Valves / tubes - Semiconductors » VALVES/TUBES / SEMICONDUCTORS in RADIOMUSEUM » Replace 1L6 with DK92
           
Michael Watterson
 
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28.Feb.13 18:07

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The DK92 is reasonably available. the 1L6 may not be available. The DK92 does use same filament current (series operation) and is much better for HF than DK91 or DK96.

Wires at pin 5 & 6 would need to be swapped. Some forums suggest this is successful for a Zenith Transoceanic, but I have not tried this myself.

 

Udo Janssen
 
 
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01.Mar.13 21:11

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HI Michael,

yes a replacement of a 1L6 tube is possible with a DK92 in a Zenith Transoceanic. The heater current is the same. It will work without a change of the wires of PIN 5+6. Because of the different capacities of some pF you have to align all the shortware circuits. The last shortwave band (18 Mc) may not work properly because the new alignment will not work without changing the coils.

Best regards from NorthWest Germany

Udo

This article was edited 01.Mar.13 21:11 by Udo Janssen .

Michael Watterson
 
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03.Aug.13 21:47

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Dear Udo, of course you are correct, I had only looked at the pin names, not functions!

They are different structures. Unless the 1L6 is really an octode and a final suppressor grid is not shown, the DK92 has no isolation grid between Oscillator out and Mixer in but a Suppressor grid on the Mixer section.

Though the names g3 and g4 are reversed on pin 5 & 6 these are not the same functions

1L6 DK92 Both  
Name C pF* Name C pF Function Pin
f- -- f- -- filament - 1
p 12 / 7 a 8.4 IF out (mixer out) 2
g2 2.6 / 2.6 g2 4.8 Osc out 3
g1 2.2 / 2.2 g1 3.9 Osc in 4
g3, g5 -- g4 -- Screen (fixed HT) 5
g4 7.5 / 7.5 g3 7.7 RF in (mixer in) 6
f+ -- f+, g5 -- filament + 7
Osc to RF 0.24 Osc to RF 1.6  L.O. Leakage to RF  
RF to IF 0.36 / 0.46 RF to IF 0.46  (6 to 2)  
g1 to RF 0.19 / 0.19 g1 to RF 0.2  (4 to 6)  
g1 to IF 0.1 / 0.15 g1 to IF 0.11  (4 to 2)  

(* Shielded / Unshielded, external shield wired to pin 1)

We can see that the different grid arrangement means there is more L.O. leakage likely on RF input, 1.6pF vs 0.24pF coupling, but where there is an RF pre-amp this is not a serious issue. The g2 (Oscillator psuedo plate/anode, drive) is about 2pF more, but the Oscillator is usually tuned on g1 which is about 1.5pF more. Very slight realignment on the highest band of the high frequency end Oscillator trimmer may be needed. Coils, IF and RF should be unaffected.

In Europe the DK40 (a sort of Octode) was used from 1948 for better than 1R5 performance. This was then replaced in sets requiring good Shortwave in 1952 by the DK92.

Next is to test the 1L6 and swap with a comparable emission DK92 (we have access to AVO VCM163 and Ronald Dekker's uTracer) then test the relative performance and shift of frequency on the highest band and highest frequency. Then a head to head test between my friend's Zenith TO 600 (like this) and my  PE94MBQ/LW  set.  I have also one model using a DK40, but it has no RF preamp. 

This article was edited 03.Aug.13 22:19 by Michael Watterson .

  
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