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Old 5th September 2012, 09:23 PM   #1
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Question PT laminations are usable as OT laminations ?

I've a pair of unknown transformers (may be 250/350W) in very good shape, I think they were recovered from a pair of inverter power supply (so unknown and probably unusable voltage ratings)

I've also some old PT that are in bad shape (and must bee rewound as to be usable)

I'm wondering if the laminations of this transformers are usable to build bass and/or guitar OT (I need a big OT as to use some GU50 tubes I've for a very big amp)

Thanks

K
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Old 5th September 2012, 10:01 PM   #2
DF96 is offline DF96  England
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Probably, yes, OK for bass or guitar. Power laminations can sometimes be thicker than hi-fi OPT laminations, as the higher the frequency the thinner the lams.
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Old 5th September 2012, 10:22 PM   #3
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seen some microwave over transformers with very thin lamination's.
and those transformers you can get from most scrap yards easily.
they go from 800watts to 1600watts+
so they could be suitable to rewind if you are worried about transformer size.
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Old 5th September 2012, 11:38 PM   #4
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most microwave xfmrs that I have seen have welded lams!



And are of the split bobbin type... not the standard EI...

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Old 5th September 2012, 11:53 PM   #5
TheGimp is online now TheGimp  United States
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Take a die grinder to the weld. I've disassembled several small transformers by using a dremel tool.
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Old 6th September 2012, 12:19 AM   #6
AJT is offline AJT  Philippines
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laminations that are 0.35mm thick are generally better than laminations of 0.5mm thickness...
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Old 6th September 2012, 02:29 AM   #7
DUG is offline DUG  Canada
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Most power transformers (50/60Hz) are made from material that will have very high core material losses at audio frequencies. Generally above about 200 Hz.

400Hz power transformers are not made from the same material as 50/60 Hz ones.

Good luck
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Old 6th September 2012, 03:01 AM   #8
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In addition to usually being welded, MW transformers are designed for mainly harmonic current, accounting for their unusually high power rating for such core volume. The coils are usually saturated in very strong varnish and would have to be cut off. The core material is usually not very high quality even though they may be slightly thinner lams than everyday 60Hz transformers, and would have a lot of loss in the high kHz.. To reconfigure with full interleaving would take a ton of work to remove all the burrs after separating the welded I's from the E's. End result: probably not worth it for audio output.
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Old 6th September 2012, 04:01 AM   #9
AJT is offline AJT  Philippines
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single ended opt's can use such welded MW transformers.......
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Old 6th September 2012, 04:32 AM   #10
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by Kagliostro View Post
I've a pair of unknown transformers (may be 250/350W) in very good shape, I think they were recovered from a pair of inverter power supply (so unknown and probably unusable voltage ratings)

I've also some old PT that are in bad shape (and must bee rewound as to be usable)

I'm wondering if the laminations of this transformers are usable to build bass and/or guitar OT (I need a big OT as to use some GU50 tubes I've for a very big amp)

Thanks

K
The frequency range of a guitar is about 80Hz up to about 8KHz. The bass goes down to 40Hz and also up about as high. But in HiFi terms there are no "highs" so don't worry that the PT laminations will be rather thick compared to what a HiFi OT might have

As a rule of thumb just figure if you have a 100W PT that it will be good for only a 50W bass amp or a 100W guitar amp

One question is the size of the window. A OPT will have many more turns of wire and it will have a few taps for 4, 8 and 16 ohm speaker loads
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