Centrum 4WGS

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Centrum 4WGS

Postby Racing on Mon May 30, 2016 10:58 am

Thomas Jaeger of Monolord dropped one of his Orange amps off for service a couple of week back,to be up to snuff before hitting the road again,and as he did he dropped this power house off too with the wording;-" It´d be neat if you could get it working again"-

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This is by any measure a really small amp. Small on power too.
That mega heffa cylinder poking out to the one side in turn is the mic transformer from hell...

I just did a Centrum type 517 which i presume is from the mid/late -40s and this thing strikes me as older. Have written the manufacturer,Gylling,which is still in business asking for any additional info on them.

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Not much to Q to be honest huh?

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Yup. As dead on arrival as they come i guess. No fuses what so ever.. Uses a 5Y3 for rectification,a pair of 6J7´s as preamp and in turn a rather odd 6G6 for driver/power.

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In short some idiot Mr Handyman had been at it. As the amp´s hardwired..only one thing to do really and that was to write the topology down and go at it. Cleaning time in short.
Mods kept to an absolute minimum this time out.

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Stock smoothing was via one of them multisection e-lytes,which was of course as dead as they come. Replaced that with all in all 4 axials of 22µF. Glued them in there,and secured them with ty-wraps.

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Yes. An aircastle. Comes with the territory when we´re talking hardwiring. That it comes out a bit clustered is as the chassis is REAL small.

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That spare hole in the faceplate was handed an input jack.

Now...the 6N6G is referenced at approx 4 watts and i had real troubles even extracting that all said and done. Final answer was 3,25 watts.. :shock:

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I believe much of it can be attested to this real minescule little OT. No idea of output impedance...why i noodled around with that for a bit.

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In general most of it is stock per se,just with components replaced. The tonecontrol though has been reset to do its thing earlier then on the stocker,which made hiss and hum come down quite a bit.
OT has been replaced as you can see. Had a few small SE´s laying around...

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A few fuses were added. FTW!

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The two tubes on the left are the 6J7´s. The rearmost one having its shield half way off. Then the 6N6G and behind that in turn the 5Y3.

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I guess this pic gives you an idea of size. The 6N6 is about the size of an old coke bottle 6V6/6L6 approx.

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Yep. It isn´t exactly a beutiful amp. True that.

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The Toshiba 5Y3 has obviously been replaced before and as it turns out...shorted. Replaced that and the amp was up and kicking again.

So?
Well,i cascaded the two 6J7´s and let them head into the driver stage of the 6N6. All in all that made this thing come out as a sort of JMP at full blast all said and done.
Neat little amp!
3.25 watts tho..doesn´t exactly make for a massive powerhouse :lol:
Last edited by Racing on Sun Jul 10, 2016 7:48 pm, edited 1 time in total.
Racing
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Re: Centrum 4WGS

Postby Racing on Tue May 31, 2016 10:20 am

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Threw yet a few tweaks at it and apart from making the quoted power it now also sounds all it can.
Fabbed a small "floor" for it and installed a set of feet.
Yep. There´s a small switch added to the faceplate,where you can opt to make it roar even more :mrgreen:

Seing its size i haven´t added a handle. Thomas will be back soon enough and gets to make that call.
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