WSW 913

Burns, Selmer, WEM, and more

WSW 913

Postby Racing on Fri Jun 19, 2015 12:19 pm

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Picked this up for about a song. It´s dubbed something as unsexy as WSW 913/1 and is by "Wiener schwachstrom werke". In essence Austrias part of what became Siemens.

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Indeed. Now. Knowing that Siemens made some highend studio stuff at the time and god knows what else i expected something out of the ordinary,and..got a mouthful.
The straight up answer is that this can´t do. As it turns out WSW has opted to run the amp via rectifying direct wall voltage. Hence..

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The powertransformer to the right is even smaller then the output ditto. IOW..this amp can not take the install of a 3 prong jobbie as is and that is downright simply unacceptable. Or more to the point it is NOT something that´ll leave my shop as is.
Seing that it was manufactured back in 1957..no wonder maybe,but regardless this is a no-can-do. Ergo,replacement of power tranny is up and i´m going to use one out of a scrapped old Eminent. Provides about the same voltages,and this then through a proper powertransformer which brings that the amp,first of all,is galvanically separated from the mains net. Something that is downright essential.

That said..it IS an interesting solution to someone like me to dwell over. Never seen the likes of it. One side of the mains voltage hits the selenuim rectifiers,which are of 130mA capacity a piece-there´s four of those,and the other end of it hits the PT via a fuse. Real peculiar setup.

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Seing that i for one hopefully know what i´m doing i´ve played around with the amp on the workbench and have at least got it up and running. The stock onboard e-lytes for instance check out as new on my ESR meter!! Now THAT`S quality for ya!
´N yeah. It provides sound. Fair enough.

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Here the four main selenium rectifiers. Yeah. Totally PTP built,in the true meaning of the word.

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Yep. A pair of EL-34´s. The good ol´ stuff even.

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The actual preamp has seen some work previous me. Not for the better as the one that´s pulled this off has missed the mark as far as e-lyte voltages with approx 100VDC. IOW...grenade warning...

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Yeah. I know. Looks real complex,and is for that matter. Anyways. As this turned out to need work in a manner i wasn´t aware of...i´m gonna back down on this one for a short while and regroup a little.
The implement of the old Eminent powertransformer will take a bit of sheetmetal work i bet,and seing that i might as well just clean house and take it from there. I my usual "hotrod standard" i wanna keep the looks of the amp. That is downright imperative to me. The innards tho...safety first,and that brings that powertransformer swap. That simple.
Racing
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Re: WSW 913

Postby Racing on Wed Jun 24, 2015 10:53 am

Right.
Played around with the amp on the bench a bit and got it to work. Sadly enough it does use direct wall current to run the amp in parts,and that brings a swap of powertransformer as anything but a completely galvanically separated amp is out of the question.
What´s more,TBH,the sound out of it was really so-so at best.

So.
Push came to shove.

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Had a PT on the shelves that fit,however not in the best of manners. Seing the rather low build profile of the amp that brought that a new PT could only be installed one way really.
If that is to become an issue remains to be seen,and if it does i guess the next logical step is to move one of the transformers a bit and install a shield between them out of ferrous metal.
That cluster/bundle of wires stickin right out in turn...is the stock loom for speaker out. It will be replaced IOW.

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The rectifying and bias setup as set atop the PT. All good i guess,and what was needed around the powertubes in turn was installed right atop them. Yep. Only one stand,and thereby nut,why the piece of paxolin will be fixed by strands of heavier gauge wire running between the board and pin 6 of each tube.
Trimpot in turn is for heater balance.

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Compact living :mrgreen: . That board there now holds all what´s needed for one longtailed pair,two stages of an ´83 and in turn what´s needed to run an 86. Atop that..smoothing caps and drop resistors :shock: .
Again. Seing the rather compact build and that the chassis is put together as substructures that brings that space is limited to say the least. From a design point of view in turn i´m not all happy about the sides of the chassis being out of steel and the "braces" within out of raw aluminium. The chassis in turn is bolted together.. Steel vs aluminium and galvanic forces... Well. It certainly could be better.

That said.
Fired the thing up and got a reading of approx 490VDC @34mA a tube. This number will dip a little when the preamp is setup too,but suffice it to say that B+ is up there.
The PT in turn had taps for 13-0-13VAC and..what i did was fab a voltage doubler. IOW...the 26VAC raw turned into approx 70VDC after rectifying,and that certainly suffices as far as bias voltage.

All in all the amp feels like it´s coming full circle. TBH not all that much of the stocker remains,but hey.... Exterior tho..still remains to be settled on. Stock the various jacks resides on the chassis sides and i ATM see no reason to change that. In turn only two speaker out will be set. 4 and 8 Ohms. So..from the looks of it,two jacks on each side of the amp. 2 for input and 2 for output.
Racing
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Re: WSW 913

Postby Racing on Fri Jun 26, 2015 7:04 pm

So.
An issue arose in that i had a hum from the fact of the powertransformer being to close to the output ditto and oriented in the same way/direction.
Not good,and to be expected to be honest.

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So. What i did was to reset the position of the OT by the use of stands and placing it the other side of the piece of sheetmetal that makes for the chassis. That AND turn the thing 90deg. Net result?
Still as a friggin mouse..

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As stated above there´s certainly a difference in law n order under the hood now. Mere visual logic tells a lot of the story i believe.

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By necessity the paxolin boards has been installed skewed. Simple fact is that the profile height of the amp is rather low so...

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As i´ve touched on the amp chassis is kind of thought of in modules. Brings that the actual tubes has a cmpt of their own too. Heatshield included.

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In turn ditto for the pots and components to go with ´em. Enclosure,sort of.

That said,please stand by...right now uploading a YT video of it in this "evolutionary" state...
Racing
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Re: WSW 913

Postby Racing on Fri Jun 26, 2015 8:28 pm

https://www.youtube.com/watch?v=YYg1XiyO27A&feature=youtu.be

There ya go. As the sayin goes "a work in progress".
Racing
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Re: WSW 913

Postby trobbins on Fri Jun 26, 2015 9:00 pm

Do you use an extractor for those EL34's - it can be pretty hard on the valve trying to insert and extract when only the glass can be gripped.
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Re: WSW 913

Postby Racing on Fri Jun 26, 2015 9:42 pm

No need.
It just works :D
Racing
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