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Re: [Amps] la-1000 what to convert to?

Subject: Re: [Amps] la-1000 what to convert to?
From: "Will Matney" <>
Date: Tue, 06 Jun 2006 15:42:14 -0400
List-post: <>
On using the Russina or Yugoslavian tubes (EL509-EL519), the sockets need to be 
modified for proper operation. The tubes pins are slightly thicker than the US 
6KG6A tube. The sockets need to have the contacts slightly spread before 
installing the tubes. They should NOT be force fit into the sockets. This 
caused some failures in some amps I know about because of this. What happens is 
where the pins are under stress and the tube is warmed up and cooled several 
times, the stress causes a crack in the glass at the pins thus allowing in air. 
The modification can easily be done by using the lead of a 1N5408 diode, and 
using it to spread the contacts by forcing the lead into each of them. A slight 
rocking of the lead is about all that's needed, maybe 2-3 times at the most. 
Afterwards, the tube should go in the socket the way it supposed to. The 
Russian sockets (all ceramic) may not require this, but they're not PC board 
mount which is what you need with the FAR boards. Generally, yo
 u re-use the old sockets from the amp. Just keep in mind that the tube should 
be inserted with a small amount of resistance, not a lot as you would have 
before the modification.



*********** REPLY SEPARATOR  ***********

On 6/6/06 at 3:15 PM Joe Subich, W4TV wrote:

>The Svetlana tube was the EL509 ... The old Svetlana web site 
>used to have a technical bulletin covering the conversion.  
>Will is correct ... Far Circuits still shows the PC Board set 
>or the conversion, including a tuned input board and new power 
>supply board. and scroll 
>to the bottom of the list.  The EL509/6KG6A conversion tech 
>note is available here: 
>W6TC who I believe is a member of this list is listed as one 
>of the authors of the tech note.
>   ... Joe, W4TV 
>> -----Original Message-----
>> From: 
>> [] On Behalf Of Will Matney
>> Sent: Monday, June 05, 2006 11:41 AM
>> To:
>> Subject: Re: [Amps] la-1000 what to convert to?
>> Chuck,
>> Why not convert it to run on four 6KG6A (EL-519) tubes? 
>> There's replacement boards available from FAR Circuits if I 
>> recall. To be honest though, they ran those four 6LQ6 tubes a 
>> little too hot at that anode voltage. A better voltage is at 
>> 900 Vdc. I guess they were thinking squeeze all you can get 
>> out of the four but the tube life isn't as good. A couple of 
>> 6KG6A's will do approximately 275 watts PEP so four should 
>> get you 550. I built several grid driven units using these 
>> and that's about what I could get without the anode cherrying 
>> up. That's something else to keep in mind also. A sweep tube 
>> does not act like a broadcasting tube where the anode can get 
>> red hot. A sweep tube will start to fail considerably after 
>> the anode starts to get red one time. Adjust the drive for 
>> full output from the amp with the bias backed off to about 
>> -100 Vdc. I used the bias as a hi/lo circuit varying it from 
>> about -100 to -150 Vdc with a variable supply. The EL-519 
>> tubes are about $15 to $20 eac
>>  h now I think.
>> For any interested in building one of these that is grid 
>> drive, below if the following approximate circuit voltages I used;
>> Anode voltage: +900 Vdc @ 1 amp
>> Screen voltage: +450 Vdc (from center of plate voltage doubler)
>> Control voltage: -100 to -150 Vdc (250 mA)
>> Heater voltage: 6 Vac @ 2 amps each
>> Best,
>> Will
>> *********** REPLY SEPARATOR  ***********
>> On 6/5/06 at 9:37 AM Partain, Chuck wrote:
>> >I have a orig la-1000 amp supply laying about and figure for 
>> this winter,
>> >that might be a good project to tear into. 
>> >Parts collection will start soon. I see a few folks have converted to
>> >ceramic tubes, russian glass or whatnot.
>> >anyone do any of these? and what might you suggest is best?
>> >
>> >on a REALLY good day I can see ~500w out of the  4 sweeps!!!
>> >
>> >1100v at 1 amp I THINK the transformer will do, I don't want 
>> to replace it
>> >yet.
>> >
>> >
>> >ka1mwp
>> >_______________________________________________
>> >Amps mailing list
>> >
>> >
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