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26th Jun 2022, 2:30 pm
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#1 |
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Nonode
Join Date: Dec 2012
Location: Bocking, near Braintree, Essex, UK.
Posts: 2,071
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Sobell 518
Hi folks
I recently obtained the Sobell chassis of which I found it was the 518 model, the chassis is a bit rusty but have cleaned it up quite a bit, I also found electrolytic capacitors lashed in on top of the existing ones so in progress of sorting all of those out. The one thing that is puzzling me is the S7 which is part of the wave band switch assembly has been disconnected now I need to find out why some how. The problem being of knowing why and who did it is a complete mystery at the moment, if anyone has had dealings with this particular model it would help. Will put some pictures of it in progress later Ken |
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26th Jun 2022, 5:19 pm
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#2 |
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Moderator
Join Date: Dec 2010
Location: Exeter, Devon and Poole, Dorset UK.
Posts: 6,865
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Re: Sobell 518
Has the switch been bypassed?
If the circuit your using is the ERT then S7 switches the HT off to the front end when in Gram mode. It could be that the switch was tracking across the wafer so was bypassed. The circuit is the same on the 516. I restored a 516 decades ago and that had the switch bypassed long before I got it. Cheers Mike T
__________________
Invisible airwaves crackle with life or at least they used to  Mike T BVWS member. www.cossor.co.uk |
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26th Jun 2022, 5:48 pm
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#3 |
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Nonode
Join Date: Dec 2012
Location: Bocking, near Braintree, Essex, UK.
Posts: 2,071
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Re: Sobell 518
Hi Mike
At the moment it would seem the way you describe but I am going to put pics on here as I progress, the switch wafer does not look as if it had been tracking, it just looks as if it can do with a clean. Here are pics so far. More to follow. Ken |
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29th Jun 2022, 7:01 pm
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#4 |
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Nonode
Join Date: Dec 2012
Location: Bocking, near Braintree, Essex, UK.
Posts: 2,071
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Re: Sobell 518
Here is another picture of the Sobel 518 in its progress of getting toward the final stages. Just got to wait for the smoothing cap to arrive and find two dial light bulbs
Ken |
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2nd Jul 2022, 8:54 am
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#5 |
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Nonode
Join Date: Dec 2012
Location: Bocking, near Braintree, Essex, UK.
Posts: 2,071
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Re: Sobell 518
Hi Folks
Have now got the smoothing cap in but powering the set up and checking the Anode voltages on each valve V1 173V, V1 triode section 62V, V2 198, V3 58V, V4 169V. The waxies have not been changed though and I suspect some of these may be dragging the HT down. The Kathode of V5 with respect to the HT seems reasonable. So just a matter of obtaining capacitors to replace all of the wax ones. Ken |
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6th Jul 2022, 11:08 am
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#6 |
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Nonode
Join Date: Dec 2012
Location: Bocking, near Braintree, Essex, UK.
Posts: 2,071
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Re: Sobell 518
Hi folks
In trying to find where the HT on this set is dropping off I took all valves out except rectifier and one by one put each valve back in and each time measured the HT on the anodes, it appears that when I put the frequency changer back the HT dropped dramatically and now suspect this valve and or the components that surround it. Ken |
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