Changing an amp to US voltage ... how straight forward? JCM900 Mark III MV

SquireJapan

Don't suppose anybody knows how straight forward it is to change a JCM900 Mark III to be US voltage (from UK). It's the one I'm selling in the classifieds.

I might end up in the US for a little while, hence thinking about what I might take with me (or not).

If it's trivial, great, I'll get it done. If it's any kind real hassle, I'll just leave it here .

EDIT: Some more research has pointed me towards "taps" that can be used on the transformer. Practically that sounds ideal, but I can't find where/how to find out if my amp has these "taps" and how to perform the change.

Happy to pay someone here or in the US, but not sure where to start...

Thanks ...

ICBM

Very simple on these amps, the PT has a dual 120V primary winding - connected in series for 240V and in parallel for 120V. You just need to move two connections to change the voltage.

Best to get a tech in the US to do it so he can give the amp a once-over after shipping too, just to be on the safe side.

SquireJapan

Amazing!!!


Thanks ICBM - you've no idea how much time I've spent trying google and and make sense of things ...

Ta!

ICBM

If it helps - this is the schematic for the 100W power stage (the 50W is identical but with only two power valves):

http://elektrotanya.com/PREVIEWS/63463243/23432455/marshall/marshall_jcm900_100w-power-amplifier_sch.pdf_1.png

At the lower right you will see the power transformer, which is the double stripe with seven black 'blocks' next to it - these are the windings. On the left-hand side you will see the two primary ones, which are connected in series with a link wire between two dots. To run the amp at 120V you disconnect this, then connect the two in parallel instead by connecting the bottom of the upper winding to the bottom of the lower one, and the top of the lower one to the top of the upper one.

Any tech should be able to do this in a couple of minutes once inside the amp, so it's not an issue for sending it to the US.

SquireJapan

Absolute legend!