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Old 24th March 2012, 12:07 PM   #81
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I don't think any description is required

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Old 24th March 2012, 08:32 PM   #82
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There is obviously a typo: it is not 220v @ 9A but rather 11,36A

Also the lines in Italy are 230v but my mains are more like 225v. So all voltages are bumped by 2.5% and this is quite useful as more filters will be added to avoid "motorboating" and such. Thse will be RC filters so a small drop in resistance is to be taken into account.

the small transformers will power the 4 866A tubes.
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Old 27th March 2012, 12:20 PM   #83
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I have a couple of questions for you guys. Hopefully someone will provide some much needed answers:

1. The 2500va is indeed large with a 1,3kv secondary. I will be fitting it inside the case behind the gu81m sockets with a through hole bolt. Obvioulsy I will avoid creating shorted secondaries but I was thinking: would there be a positive, tangibile improvement if I were to shield the transformer with some sort of "cover"? I could have a copper form made to cover the transformer. would it be worth the cost?

2. I decided not to use the large rectifiers for now. The mounting mechanism I devised is not sturdy enough for my taste and I still haven't found aesthetically pleasing material to make heat resistant grommets...I will use 866A or xenon or other ux base rectifiers.
This takes me to another question. I will end up having a separate transformer for each pair of 866A. The CT will then have its own choke. Provided the windings are separate (ie: 1.25 - 0 - 1.25 + 1.25 -0 - 1.25) could I have all power filaments on the same (adequately sized) core? I suspect so but it would be a pitty to have something of the sort made only to dicover adverse effects.

I hope I managed to explain myself correctly

Thanks
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Old 27th March 2012, 12:37 PM   #84
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What a monster!
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Old 27th March 2012, 01:19 PM   #85
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yep...big indeed. 2500va HV core, 650va LV core, 1700va output transformers....a lot of copper. I would however like to reduce waste and increase efficiency, that is why I'd like to have all gas rectifier power filaments (and center taps) on a single core. As much as this will not benefit the current build it will definitely be handy for the next one (GM100 push pull maybe?)
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Old 25th April 2012, 06:38 AM   #86
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output transformer... ready for testing!

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Old 26th April 2012, 01:45 PM   #87
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just some superfun time with gm100

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If anyone is itnerested I am sellhe transformer is my gu81m filament xformer. Perfect response even when powering two gm100 tubes. Only problem the car battery cables get so hot the voltage falls from 12.6v to 9v
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Old 27th April 2012, 09:58 AM   #88
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back on topic...

6x 3b28 to allow for side operation of the amp. These will just be used for testing (mercury tubes cannot be used sideways) and then replaced for the final 866A tubes)

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very nice rugged construction.

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Last edited by Alexontherocks; 27th April 2012 at 10:01 AM.
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Old 27th April 2012, 10:53 AM   #89
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XENON glow 400mA 50v

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Old 8th May 2012, 02:33 PM   #90
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old photo of minor progress....

panel is off to get painted

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The caps together with the rest will be under the chassis.

maybe this weekend I'll manage to fire up all the voltage boards.

You can see the output transformer and filament transformer thrugh the socket holes.
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