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Always searching EL51 tubes or replacement solution !
Geschreven door Thierry Magis om 13. Jul 2001 22:21:56:
Hello !
In order to restore my old 2844 Philips amps , i'm always searching 2 pairs of EL51 (old power pentodes) ...
I've search in a MBLE data replacement book from the 60's ; but there is no direct replacement type. Can I use others power tubes , with modify the amp?
The EL 51's are use in push-pull to obtain 60W power level. Output transformer impedance is about 7000 ohm anode to anode. Second grids are connected directly to +530V (no taps on transformer); first grid is driven by a little transformer coupled with separate windings from the output transformer. The cathodes are common polarised by 144 ohm/16µF.
Secondary of the output transformer is multi-tapped : 7V/0.8ohm ; 12V/2.4ohm ; 20V/6.7ohm ; 35V/20ohm ; 60V/60ohm ; 100V/167ohm.
I've think to use 6550 tubes ; but it works with other load impedance... Perhaps using the output transformer with higher loudspeaker impedances to increase the reflected load to anodes?In case I don't find the EL51 tubes , can i re-use the output transformers with other circuit and available tubes (6L6GC ; 6550 ; KT88)?? I've never find a circuit diagram using a transformer with this primary impedance...
Thanks for helps and advices !
Friendly greetings,Thierry