[AMPS] SB-1000 converson with QB 3.5/750 ???????

[Rich Measures]

>
>Hello All,
>
>For a friend of mine I need some info.. He blew out his 3-500Z.........

What is wrong with the tube? 
>
>Can anyone tell me if it is possible to put a QB 3.5/750 in a SB-1000 instead
>of the öriginal 3-500Z
>This QB 3.5/750 is a Tetrode but possibly with all grids to ground it should
>work ??? any info would be very helpfull.

It should work if each of the three grid pins are RF grounded through at 
least 470pF per pin.  The dc grid currents can be carried by two 1/2w 30 
to 51 ohm resistors, one from the screen to ground and one from the grid 
to ground.  Another method is to direct ground the two screen pins and 
direct ground the grid pin.  However, this arrangement offers no grid 
protection.  
>
>Heater voltage is the same and so is the cutrrent bouth arround 14-15 Amps @
>5V
>also same pinning and it seems the socket is the same too...
>
-  later,  John

Rich. Measures.,www.vcnet.com/measures, 805.386.3734


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