[Amps] 3-500Z convertion

[Jan Erik Holm]

As far as I remember you can not run 4X500´s in zero bias GG,
you will not be able to get correct ZSAC for linera operation.
4X500´s need screen and grid voltages to get correct operating
point.

4-250A or 4-400A or C is OK in SB-220. Just tie all grid pins together
and ground them directly, also you must short out the "bias"
zener diode to get correct ZSAC, maybe adjust with a string of
diodes to get correct ZSAC.

73 Jim SM2EKM

PS: Think I remember that some 4-400´s was a bit too tall for
the PA compartment lid to fit, 4-250A is never a problem.
---------------

Hsu wrote:

> Thanks Peter!
>     I have got a a died  TL922  as a junk,I only pay $100 for it.so I don't want pay for it too much.Althought the 3-500Z are made in China, but I call the factory, They ask me pay $500 for a matched pair!Mr.Richard L. Measures have mentioned in the list that  3-500Z can replace by 4-400(need some work),I have a pair  4-400C, but I just test them, they all died!in this weekend, I check my junk box, and find out some NOS Chinese FU-500Fs(same as 4X500A) and its socket, I just read its datasheets , I found the screen and grid  dissipation power not too small, so,I think maybe it can work in GG and cathode drive.It have same  volt and cureent of   filament as 3-500Z.  
>   73! Hsu 
> 
>   
> ----- Original Message ----- 
> From: "Peter Chadwick" <g3rzp at g3rzp.wanadoo.co.uk>
> To: "Hsu" <Jbenson at sohu.co>; <amps at contesting.com>
> Sent: Sunday, July 23, 2006 7:14 PM
> Subject: Re: [Amps] 3-500Z convertion
> 
> 
> 
>>Hsu said:
>>
>>>My TL922's 3-500Zs died,I have some 4X500As,it seems the 3-500Z can convertion by 4X500A, <
>>
>>The 4X500A is an external anode tube, so the cooling won't be right, it needs a different socket, and it's a tetrode. You'd need to do soem careful calculation to determine if the grid and screen dissipations would be exceeded. All in all, i'd say buyin a pair of new 3-500Z is a better way to o.
>>73
>>Peter G3RZP
>>
>>
>>
>>
>>
>>========================================
>>Message Received: Jul 23 2006, 11:54 AM
>>From: "Hsu" 
>>To: amps at contesting.com
>>Cc: 
>>Subject: [Amps] 3-500Z convertion
>>
>>Hi, I'm a new member.My TL922's 3-500Zs died,I have some 4X500As,it seems the 3-500Z can convertion by 4X500A, Does anyone have this experience?Thanks in advance!
>>73! Hsu
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