Happy new year to all of you.
A friend of mine recently bought a Marshall 9100 (2x50W rack power amp). This amp was designed for 220V operation an has no voltage selector switch, so he runs it with a huge (really huge) 110V to 220V converting trafo.
I told him that he can convert the amp inside at the power transformer for 110V operation.
After I opened the amp there are 2 power trafos (1 per channel) with the cables on the 2 primary windings in series. If I connect those 2 primaries in parallel, the amp should work with 110V.
Attached is a photo of one of the transformers: Note the brown wire coming from one primary winding and going into the other primary winding: windings are in series. If I cut this wire and connect one side of one winding with the same side of the other winding, bot windings should be connected in parallel.
Is my assumption correct? I don't want to blow an amp that isn't mine.
A friend of mine recently bought a Marshall 9100 (2x50W rack power amp). This amp was designed for 220V operation an has no voltage selector switch, so he runs it with a huge (really huge) 110V to 220V converting trafo.
I told him that he can convert the amp inside at the power transformer for 110V operation.
After I opened the amp there are 2 power trafos (1 per channel) with the cables on the 2 primary windings in series. If I connect those 2 primaries in parallel, the amp should work with 110V.
Attached is a photo of one of the transformers: Note the brown wire coming from one primary winding and going into the other primary winding: windings are in series. If I cut this wire and connect one side of one winding with the same side of the other winding, bot windings should be connected in parallel.
Is my assumption correct? I don't want to blow an amp that isn't mine.
Attachments
It'll probably work fine as you say, but there's no absolute guarantee. I'd feed a bit of low voltage into one of the windings (say 12 V AC) and check you get exactly the same on the other winding; you probably will. It's the sensible way to wind a power transformer. Then, make absolutely sure you get the polarity of the windings right, and you can connect them in parallel.
If the conversion is by autotransformer (no isolation) it doesn't have to be as big as all that (still quite heavy, though).
If the conversion is by autotransformer (no isolation) it doesn't have to be as big as all that (still quite heavy, though).
Agree and add: build and use a lamp bulb limiter, a 100W bulb should be fine for that amp, when you turn amp on (already wired for 110V), bulb should blink, then cool to barely visible orange, which means current consumption is not excessive.
If it shines bright and stays so, you have a problem, but the lamp bulb will avoid damage.
Light Bulb Limiter
If it shines bright and stays so, you have a problem, but the lamp bulb will avoid damage.
Light Bulb Limiter
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