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Old 29th February 2004, 04:43 PM   #1
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Default schematic for a push pull EL 509

I have two EL 509 + an output transformer (impedance about 9.000 ohm) utilized in a 2xEL 503 push pull amplifier. Id like to build a push pull amplifier utilizing these valves and that output transformer.
Can somebody help me? Where can I find a schematic for a push pull amplifier with EL 509 ? or, alternatively, which values (anode voltage, current, and grid) Id utilize to adapt EL 509 to the present circuit employing EL 503 (not available) ?
Many thanks.
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Old 1st March 2004, 02:25 AM   #2
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Hi,

The OPT you have isn't an ideal match for the EL509 but have a look here:

EAR

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Old 1st March 2004, 05:01 AM   #3
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Thanks Frank for your replay.
Some precisations.
The amplifier I have is a push pull with 2 valves EL503.
I do not have EL 503 any more. However, now I have EL 509. So I'd build a push pull with EL 509.
My problems are:
1) Where I can find a schematic with a push-pull with EL 509 ?
...alternatively...
2) Which values of anode volatage, current and grid voltage I'd use to adapt the old amplifier to the new tubes ?
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Old 1st March 2004, 11:55 AM   #4
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Hi,

Do you want to run it as a replacement for the EL503?

How much B+ for the output valves do you have available?

Do you want it in triode or penthode mode, Class A, AB1....?

Any reason to ditch to EL503?

I think this tube was used alot by the Italian Geloso amps...

Cheers,
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Old 1st March 2004, 12:48 PM   #5
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The amplifier is a RCF mono (for cinema).
It has been given to me without the 503s... and I have a pair of EL509 that would like to utilize in spite of the EL503s.
I include the schematic of the drive and power section ...so every answer to your questions are reported on it.
I'd be very grateful if you could help me.
With anticipated thanks

Antonio

P.S.
V2 and V3 = EL 503.
V1 = 6AN8
Attached Images
File Type: jpg rcf2.jpg (83.6 KB, 631 views)
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Old 1st March 2004, 04:02 PM   #6
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Hi,

Do you have a way of verifying the powerxformer can deliver sufficient current for the heaters of the EL509?

EL 503 = 1.2 A * 2
EL 509 = 2.0 A * 2

Cheers,
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Old 1st March 2004, 05:42 PM   #7
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I could try it... but how to verify ?
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Old 1st March 2004, 06:43 PM   #8
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Hi,

If there's no specification written on the xformer, hook up a set of clip-on leads from the heater pins (4 &5 ) on the socket of the EL503 to the EL509s.

Hook up a DVM to the same pins and set it to AC in the 0 to 20 VAC range.
Switch on the amp, if after 20 seconds to voltage sags to 5.5 V or lower and the xformer gets abnormally hot, switch the amp off immediately; the xformer can't take the load.

Cheers,
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Old 4th March 2004, 03:30 AM   #9
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I hve carried out the test.
The heaters supply is OK.

Now...The question remains ...
How the schematic would be modified to be adapted to the EL 509 ? ...and, in particular, can the output transformer work correctely ?
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Old 4th March 2004, 10:44 AM   #10
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Hi,

Quote:
...and, in particular, can the output transformer work correctely ?
Well, I really have a hard time believing the OPT has a Zprim of 9K as stated in post #1.

For a PP of EL503s I'd expect something closer to 2K4...

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