Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: DonP on March 30, 2019, 06:59:21 pm
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I have a 600-0-600v, 200ma power tranny. I'd like to build an clean amp using 6550s (I have a bunch of GE's). I'm trying to figure out which output tranny to use.
The GE data sheet for a 70w I'm looking at says I need an ultra linear 4000ohm, but the plate voltage should be 450, and the max current could be 265ma + 38ma.
I'm thinking this isn't going to work because I have too much voltage and too little current.
If I don't use a tube rectifier will I have more current? I guess the comes with even more B+ voltage however.
I'm open to any ideas.
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That PT will give you about 850VDC unloaded. I'd forget about using it.
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Any idea of what it was used for? I has a 5v 3A tap for a full wave tube rectifier.
The Hammond 1650R looks like the right OT. 5k with UL taps.
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You want to use a single pair of 6550's?
You don't have to use a UL OT.
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That 600V PT *probably* came-with a large choke rated for Choke Input operation.
That puts it near 540V DC. At 200mA it points to 5400 load. This is on-track for a pair of big tubes in the 80+ Watt range.
840V DC is just too high for sanity.
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That 600V PT *probably* came-with a large choke rated for Choke Input operation.
That puts it near 540V DC. At 200mA it points to 5400 load. This is on-track for a pair of big tubes in the 80+ Watt range.
840V DC is just too high for sanity.
Unless it was meant for HAM.
silverfox.
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(https://i.imgur.com/6UA2Yvr.jpg)
(https://i.imgur.com/gW4SDDK.jpg)
Some pictures if this might help. So if I use a large high ohm inductor I can pull down the B+ to manageable levels?
(http://www.triodeel.com/6550ap3.gif)
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That transformer is unsuited for nearly all tube amp applications. Maybe a stadium. It is also very dangerous to work with and precautions should be taken if you proceed.
silverfox.
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If it was mine I'd be surfin for parts that get me in the red :icon_biggrin:
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Can I make a laser weapon out of it?
I guess it is for transmitting tubes?
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I guess it is for transmitting tubes?
Or,
That 600V PT *probably* came-with a large choke rated for Choke Input operation.
That puts it near 540V DC. At 200mA it points to 5400 load. This is on-track for a pair of big tubes in the 80+ Watt range.
840V DC is just too high for sanity.
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Can I make a laser weapon out of it?
I guess it is for transmitting tubes?
Probably CO2, definitely Helium-Neon. Argon. Another application would be a flash tube DCV supply for solid state. About 70 Watts optical power output I'm guessing. You would want a doubler circuit.
silverfox.
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That 600V PT *probably* came-with a large choke rated for Choke Input operation.
That puts it near 540V DC. At 200mA it points to 5400 load. This is on-track for a pair of big tubes in the 80+ Watt range.
840V DC is just too high for sanity.
Well this sounds doable and in the ball park of what I was hoping for. I just need a choke that has the resistance to bring down B+ and can handle 200ma.
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I just need a choke that has the resistance to bring down B+ and can handle 200ma.
It's not about resistance. Read the third paragraph on this page...
http://www.aikenamps.com/index.php/chokes-explained
...Then google choke input filter.
When connected to a choke input filter your 600-0-600 PT will have a dc output of about 0.9 x 600 = 540V. That's what PRR was saying earlier. So, just get a BIG choke that can handle 200mA.
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...Then google choke input filter.
Sluckey- When connected to a choke input filter your 600-0-600 PT will have a dc output of about 0.9 x 600 = 540V. That's what PRR was saying earlier. So, just get a BIG choke that can handle 200mA.
Just buy a right sized transformer off ebay and get it over with. btw, what size caps do we need this?
Do you have a project in mind or just experimenting? After re-reading your OP, I would suggest, if you want to build an amp, maybe you already have, I would suggest finding the project first and then some schematics to look at. Loads here. After you find a project, see if that PT can be used.
silverfox.
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I've built amps before. In 1990 when I was young and fearless and there was no internet (just the Tube Amp books) I gutted a Marshall 4140 "Town and Country" and created the first Triple Super Lead with a a Mesa lead channel (Loved this channel!!!), a 2203 Marshall Crunch, and a Fender Clean. It worked and was very loud (4x6550s were putting out 120w clean). The issue was I used relays for all the switching, and it was a little noisy (learned that having a relay to switch between two Presence pots was not a good idea - loud pops). I took it all apart and was going to redo but it never happened. I've also built a few micro amps using a 35W4 and 50C5 power amp.
I have a Dynaco SCA-35 which I've bought Dave Gillespy's (sp?) replacement boards but haven't started it yet because it still sounds great (caps still haven't dried up).
So the idea for this project was to make a clean center channel / subwoofer to enhance the power of the SCA-35. I have 5 good GE 6550's that can handle the voltage but don't have the output tranny or choke.
But if this project sounds like a bad idea I can shelve it.
I have other trannys to make into a 2x40w stereo (I think the output trannys were spec'd for 7591A's, which I don't have).
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if this project sounds like a bad idea
:icon_biggrin:
pretty much all my Ideas started out that way, but I wound up with some keepers :icon_biggrin:
pay attention when someone says "you can but..", understand the "buts" and you might succeed, or have parts for the next grand idea