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Old 2nd December 2012, 04:52 AM   #261
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found these, might have to do a trip down to the local hardware store: Stainless Steel Round Base Plate w/ cover Suit 2" Tube | eBay

2 inches = 50mm, size of kt88 base = 48mm

and take the chassis down with me to see how they look.
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Last edited by freax; 2nd December 2012 at 04:57 AM.
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Old 4th December 2012, 03:56 AM   #262
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Is there a good reason why a 5U4-G couldn't be put in place of the GB?

http://www.fourwater.com/files/fullrect.txt

The G has a max plate mA of 225mA vs the GB's 275mA, is the schematic that tightly wound that it cannot accomodate an older coke bottle style G model?

The vdrop is different aswell, 44v on the G vs 50v on the GB, will putting a G model in substantially increase the B+ to the point that it would cause issues?

Would increasing the B+ by 6-12v make that much of a difference?

I've been thinking about ways to fuse the B+ line in the event that an older coke bottle style has an internal short, also I've read that monitoring the power transformer's temperature is a wise idea when doing things such as this.

Thank you for your advice.
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Last edited by freax; 4th December 2012 at 03:58 AM.
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Old 4th December 2012, 04:32 AM   #263
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The total current draw for this amp is approximately 150mA.

Both rectifiers will meet this specification.

The total plate supply resistance for a 5U4G is a little higher than the 5U4GB.

The power transformer secondary resistance of 50 ohms correlates with the 5U4GB at 400V.

You will need an additional 20 ohms of series resistance if you use the 5U4G.

See the data sheets for this information.

Other than that, it will work just fine.
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Old 4th December 2012, 04:59 AM   #264
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thanks for that, wouldn't the resistance of the choke add series resistance though?

scratch that, I see the schematic now and its capacitor input, so it applies.

i'm looking at the datasheets now of both G & GB.

I'll do a few simulation runs tonight in PSUD and see how much 20 ohms will need to dissipate.
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Last edited by freax; 4th December 2012 at 05:03 AM.
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Old 4th December 2012, 05:10 AM   #265
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The concern here is the series limiting resistance for the connection between the power transformer secondary to the plates of the rectifier.

A 20R/2W should be fine here, but I would make it a 3W just to keep things on the cooler side.

Last edited by scott17; 4th December 2012 at 05:15 AM.
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Old 4th December 2012, 05:25 AM   #266
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This (or something matching it) will work fine:

PR03000202009JAC00 Vishay/BC Components | Mouser

or this:

http://www.mouser.com/ProductDetail/...fEJMcOI0Q7U%3d

Last edited by scott17; 4th December 2012 at 05:39 AM.
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Old 13th December 2012, 02:30 AM   #267
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Just got my Power transformer and choke trafo, holy cow! this is heavy, Its heavier than the 600va toroidal that I bought from Antek a few months ago.

I'm still waiting for everything else to arrive (probably tomorrow)

It was very well packed.
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Old 13th December 2012, 02:57 AM   #268
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Great! Yes the transformers are definitely "beefy". Just wait until you get the OTs.

When I spec'd these to the manufacturer, I made sure they were premium.

In my opinion, the manufacturer was a little "lax" in the lamination finish, so you may want to refinish them. I've refinished the ones I've used. It's not that big of a deal to do.

Anyway, keep me posted.

Scott

Quote:
Originally Posted by freax View Post
Just got my Power transformer and choke trafo, holy cow! this is heavy, Its heavier than the 600va toroidal that I bought from Antek a few months ago.

I'm still waiting for everything else to arrive (probably tomorrow)

It was very well packed.
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Old 13th December 2012, 03:05 AM   #269
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Quote:
Originally Posted by scott17 View Post
Great! Yes the transformers are definitely "beefy". Just wait until you get the OTs.

When I spec'd these to the manufacturer, I made sure they were premium.

In my opinion, the manufacturer was a little "lax" in the lamination finish, so you may want to refinish them. I've refinished the ones I've used. It's not that big of a deal to do.

Anyway, keep me posted.

Scott
Now that you mention it, yes the core finish is quite a bit thin, I've got just the thing for it too, an epoxy paint.

That means I'll have to wait 2 more weeks before I can start assembling, ugh... the cans of epoxy are expensive, as is the chrome paint that I've been eyeing off, oh well the things we do for looks

Maybe I should rethink everything, I'll sleep on it anyway.
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Last edited by freax; 13th December 2012 at 03:33 AM.
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Old 13th December 2012, 03:26 AM   #270
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That will no doubt be great. I just use a razor blade to sluff of the high spots and finish with a poly.

When my cousin refinished his, he just smoothed them out and finished them with hi-temp semi-flat. His photos are towards the end of the Vendor's forum thread. By the way, I think we should be posting there actually.

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Originally Posted by freax View Post
Now that you mention it, yes the core finish is quite a bit thin, I've got just the thing for it too, an epoxy paint.

That means I'll have to wait 2 more weeks before I can start assembling, ugh... the cans of epoxy are expensive, as is the chrome paint that I've been eyeing off, oh well the things we do for looks
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