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 EL33A vs EL33
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 Return to top of page · Post #: 1 · Written at 6:12:48 PM on 24 August 2017.
Tombi's Gravatar
 Location: Ashfield, NSW
 Member since 29 March 2017
 Member #: 2087
 Postcount: 4

Hello,

Just (finally) getting around to looking at this Phillips 115B. The audio amp valve was missing. I think it must have been an EL33A.

This is a bit confusing as the first schematic I found was this one which indicate it is a 6V6GT
http://www.kevinchant.com/uploads/7/1/0/8/7108231/115.pdf

I figured out the 115B is different and at some point the 115 must have changed also as I found this schematic that shows it as an EEL33A
http://www.kevinchant.com/uploads/7/1/0/8/7108231/115_115a_115b_115d.pdf

So it is probably a safe bet that it was an EL33A.

Anyway - I am having trouble finding an EL33A. I can find the Mullard EL33 and the radio museum seems to indicate the EL33 is a replacement for the EL33A. http://www.radiomuseum.org/tubes/tube_el33a.html

I found a datasheet for the EL33 here http://www.r-type.org/exhib/aad0112.htm but no luck on the EL33A.

Can someone tell me if I can use an EL33? Or does anybody have an EL33A datasheet?

Does anybody have one they want to sell?

Thanks,

Tom


 
 Return to top of page · Post #: 2 · Written at 10:28:48 AM on 25 August 2017.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1378

Check the speaker transformer. If you're lucky it may have the impedence printed on it (5000 or 7000).

If it says 5000, use a 6V6GT, if it says 7000 use the EL33.

A check of the Miniwatt valve manual reveals that the only difference between EL33 and EL33A is the metallic shielding on the EL33A. In practice the EL33 should be fine.

Really, you don't have much to worry about.


 
 Return to top of page · Post #: 3 · Written at 10:52:11 AM on 28 August 2017.
Wa2ise's avatar
 Location: Oradell, US
 Member since 2 April 2010
 Member #: 643
 Postcount: 766

Even if you use the wrong tube (say the one that wants 5000 but the transformer is 7000) it will still work. It's just that you wont get as much max audio power output. But you probably would have a hard time noticing, as it would be at most 1 or 2 dB down.


 
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