Dreanaught Power Supply Requirements Will these work?

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heroesunplugged
heroesunplugged Posts: 48
edited December 2021 in Vintage Speakers
??? Have 2 old BGW Millennium 3 TMC 2 amps that have become problematic (likely from going unused for several years) and got to thinking about the possibility of repurposing the power supplies as potential donors for a dreanaught project. The case states 1000VA. The PS has 1100 stamped onto the copper shielding, but does not have a particular statement that it is 1100VA. The PS in these amps are solid. The amps do power up, but don't produce sound as they should, or with any predictable consistency. They're very dated in their use of dip switches, designed for pro audio systems and targeted to theaters and permanent installs.

All that being said, would the power supplies be potential candidates for use in a dreadnaught. They're dead quiet in the amps themselves and figured why not, given their perceived quality. The thing I'm not certain, is whether they have the correct wiring, or even understand how to determine how to properly wire one, or if I can have somebody build a couple using these, instead of buying new PSs.

Not an immediate priority, just thinking ahead and appreciate input from those that have traveled the path and understand the electrical requirements.

Have attached pictures in hopes that it will assist. If I need to remove one from the case, it should be fairly straight forward.jbhnem6tc86z.jpg
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  • pitdogg2
    pitdogg2 Posts: 24,652
    edited December 2021
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    Looks like a laminated core.
    Our dreadnoughts were a Torrid and very low noise at that. Special order only.
    They do make an 800va unit that works very well and is off the shelf.

    I do not know if a laminated core will work.
    Hopefully the guy who did all the testing will chime in.
    @DarqueKnight
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  • invalid
    invalid Posts: 1,294
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    Has to be a 1:1 transformer
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  • TennMan
    TennMan Posts: 1,266
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    I think the power supply in the amp would be a step down transformer. I believe what you need for a Dreadnought is an isolation transformer that has equal turns in both windings.
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  • DarqueKnight
    DarqueKnight Posts: 6,765
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    As others have stated, you need a 1:1 ration isolation transformer. I don't recall if anyone has successfully used a laminated core transformer for a Dreadnought. A good thing to keep in mind
    is a high current toroidal transformer was recommended by Matthew Polk in order to avoid saturation
    issues.

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  • heroesunplugged
    heroesunplugged Posts: 48
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    Thanks for the replies. @TennMan
    that makes sense. @invalid gave the short answer and @pitdogg2 has a point that laminated core type transformers may just be out of the question. @DarqueKnight is the go to on this subject. Appreciate the responses so far. Chris
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  • Toolfan66
    Toolfan66 Posts: 16,964
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    What is this Dreanaught you speak of?? 😃
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  • heroesunplugged
    heroesunplugged Posts: 48
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    Yes, it's a new thing. Not sure how, or if, that can be corrected. :D
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  • heroesunplugged
    heroesunplugged Posts: 48
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    DarqueKnight wrote: »
    As others have stated, you need a 1:1 ration isolation transformer. I don't recall if anyone has successfully used a laminated core transformer for a Dreadnought. A good thing to keep in mind
    is a high current toroidal transformer was recommended by Matthew Polk in order to avoid saturation
    issues.

    Is there a way to test a PS for 1:1 using an ohm meter?
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  • heroesunplugged
    heroesunplugged Posts: 48
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    Looks like the power supply has to be powered on and some additional test equipment is necessary to test correctly, (after the transformer has had an opportunity to warm up). That, or knowing the manufacturer's published specs.

    No big deal. Just thought I'd check and it's enough to know that this is a "no" for the "dreanaught". ;)
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  • heroesunplugged
    heroesunplugged Posts: 48
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    Thanks Polkies for your help.
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  • invalid
    invalid Posts: 1,294
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    It doesn't have to be toroidal, but it is preferred as long as it's 1:1, which a power supply transformer isn't going to be 1:1
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  • heroesunplugged
    heroesunplugged Posts: 48
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    invalid wrote: »
    It doesn't have to be toroidal, but it is preferred as long as it's 1:1, which a power supply transformer isn't going to be 1:1

    Thanks. I've moved on from the idea. Can't find any info for this particular model. The eia code 606 corresponds to Schumacher Electric Corp. Can't find the specs for these, so not worth trying to repurpose them, unless they can be used in an Acoustat interface. That's a different subject altogether.
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  • audioluvr
    audioluvr Posts: 5,460
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    heroesunplugged wrote: »
    Thanks. I've moved on from the idea.

    Good choice.
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  • engie490
    engie490 Posts: 426
    edited December 2021
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    Just buy the Avel Lindberg model(s). There's more to it than just 1:1 turns ratio. I asked Triad Magnetics about their VPT 230-4350, which can be found off-the-shelf and is 1KVa. Here are the answers I got base on the original criteria:

    1. DC Resistance of primary and secondary should be less than 0.8 ohms and preferably less than 0.5 ohms. The lower the better. Primaries are 0.393 ohms each. Secondaries are 0.444 ohms each. Therefore, you will get have that resistance with the windings in parallel.

    2. Inductance of both primary and secondary should be at least 10mH. Ideal is around 14mH. Primary inductance will be approximately 730mH in parallel. Secondary will be approximately 785mH in parallel. The material permeability can vary a great deal. The previous numbers are estimates.

    3. Current capacity to saturation should be 5 Amps minimum. Transformer is rated 8.7A in parallel.

    4. Turns ratio is 1:1. Turns ratio is 1:1.03

    Close but no cigar!
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  • pitdogg2
    pitdogg2 Posts: 24,652
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    Avel Lindberg 800va off the shelf and works ! Period!
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