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sobell: Sobell 515p valve line up - incorrect?

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Forum » Radios and other type of sets (Physics) etc. » MODELS DISPLAYED » sobell: Sobell 515p valve line up - incorrect?
           
David MacFarlane
 
 
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15.Dec.18 18:50

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Hi, I'm new to Rmorg, and not terribly sure if I am entering in the corresct fashion, nor indeed if anyone might get to see this, - fantastic and complex as the org is, but here goes -

I acquired a Sobell 515p some time ago, and have had difficulty in receiving stations on sw, mw or lw.

I tried adjusting the If's an tuning coils ever so slightly, bringing them back to where they were when I got no result.

I was about to inject signals as per textbook instruction, when I noticed that the valves seemed to be very different from the book diagrams.

The book says V1 to V5 respectively, are ECH81, EF41, EBC41, EL84 AND EZ40.

The line up in this old set is as follows - ECH81, EF89, EL84, EBF80 AND EZ80, Again, respectively V1 to V5.

I am not even sure that EL84 is in the right order, although in one of the sketches, V3 and V4 seemed to change places, which would allow EL94 to be correct.

The rest of the valves do not seem to figure, since EF41 and EBC41 are different bases.

I cannot see the similarity between EF89 and EF41, unless the bases have been swapped, but there is no evidence of this, and it seems an unlikely candidate. Can anyone help?

Dave.

Rolf Beckers
Rolf Beckers
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16.Dec.18 10:01

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Dear David,

I think there are a few discrepancies here. According to the documents we have at RMorg the valve line-up is: ECH81 EAF42 EBC41 EL84 EZ80. You mentioned your book says EF 41 instead of the  EAF 42. Does it mean you have a different book or documentation then what is shown on RMorg? In all the schematics at RMorg the valves 3 and 4 are always at the same position. Where do you see a different sequence?  You say the line-up at your set is ECH81, EF89, EL84, EBF80 AND EZ80. Is this counting according to the old valve placement? Or are there stamps or labels at the chassis showing this sequence? Anyway, if the EBF89 sits at the position of the EL84 the radio wouldn’t work at all.

In general: at the early 50s the radio manufactures changed from the 40 valve series to the 80 series. Smaller manufacturers did this even in-between the same model.

Regards,

Rolf

David MacFarlane
 
 
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16.Dec.18 12:03

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Thank you Rolf, that was a quick reply!

I had a further check on the diagrams I downloaded, and indeed, I was at an antique store in Perth (Scotland) when I picked up the original Molloy/Poole R & TV Servicing, where I found the same diagram.

I admit, after I wrote, I was further examining, and I looked at one of the chassis layouts (Not the p version of the 515), and V3 was in the back, and I had taken it to be the front.

This means the line up is V1 - ECH81, V2 - EF89, V3 - EBF80, V4 - EL84, and V5 - EZ80.

There are no stamps or labels, I think this has maybe been quite a cheap model, in a bakelite cabinet.

The discrepancies seem to be V2 and V3, and I could not decipher whether these were good replacements. This was the valve line up which came with the set, and I wonder if this is what is knocking it out.

I am about to string a capacitor onto the grid to inject a signal, and have a look with the scope, but wanted to make certain this old set hadn't been tampered with and increased its fault.

Thank you for your help thus far - it leaves me very excited about the forum - feel part of something big with common interests - Picked up an old Murphy 122M at the same antique place! Renewed the mains lead and it works beautifully!.

Dave.

  
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