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sobell: Sobell 515 still struggling

Martin Renz Ernst Erb Vincent de Franco Martin Bösch Mark Hippenstiel Bernhard Nagel Otmar Jung Eilert Menke 
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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » sobell: Sobell 515 still struggling
David MacFarlane
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26.Jan.19 19:08

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Still not terribly sure if I am doing this the right way according to forum rules, but I got the chance to spend some time with my Sobell 515P, and all of the data sheets I can find indicate that V2 is an EAF42. On my set V2 is an EF89.

This is an 8 pin base, and pulling up the comparison, I find the whole pin out to be different, and the original diagram shows L13 to be mounted on the back of the chassis.

I am wondering if there has been a lot of surgery on this model long ago (for none of it looks disturbed), or if indeed, it is a different circuit which has been employed, perhaps in order to allow the EF89 rather than the original EAF42.

The characteristics are similar, but not identical, and pin 6 is certainly not the grid on the EF89.

Any hints please?

Rolf Beckers
Rolf Beckers
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29.Jan.19 09:46
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Dear David,

It's quite normal that in the early fifties (e.g. 1952 to 1955) the tubes were changed from the 40-series (Rimlock) to the 80-series tubes (Noval).This happens at many other ratios from that period too. Smaller manufactures did this without changing their service documentation.


Rolf Beckers

David MacFarlane
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29.Jan.19 13:22

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Thank you again Rolf, now its making sense - I just found I had to go and do lots of homework with pin outs and grids, and I am getting closer to my teenage level of competency (1963), all the old data is coming back slowly from the memory banks as I renew a once keen hobby - that's the trouble with careers, they can carry you off on a huge tangent from where you intended to go, and one finally ends up in management - nothing like one's original intent.

I'm getting there, from Biasing my Marshall amp's output pairs to re - aligning the IF on this Sobell - strange sort of pleasure feeling, doing what you want!

Wonderful site and forum - thanks again.