Mesa MK IV Transformer 110/117 to 230/240 how to rewire

[DaneZ]

Hi. I have a Mesa MK IV rack mounted head with the transformer number 561141. From my research this is a multi tap transformer and the amp came to me from overseas running on 100V. I am in Australia and we have 230/240V mains power.
I am an amateur when it comes to this, having repaired some pedals and have previously rewired Studio 22 Plus amps to 240V with success.

This is a lot different to the Studio 22 Plus amps and my question is how to rewire the MK IV to run on 240V?

I understand that I need to change the fuse but is there anything else I need to do from the Power/Cap board. See pics of current wiring.

Thank you for any assistance or advice you can provide.

Dane Z

NOTE: i had to delete the original pics as I have exceed a quota. See further details below

[Jazz P Bass]

I do not have a clue what they are doing there.
Line voltage & Blue (0 volts) is what you ultimately want to connect.

[J M Fahey]

We have incomplete data from danez

Schematic kindly supplied by JPB is fine ans says all we need to know, but danez picture is not enough, since we are double blind:

1) we do not know where the wires exiting the bottom of the picture go to.

2) we do not know where the labelled solder pads on top go to.

As soon as we know both mysteries, a simplish solution can be offered; other wise options are:

3) you have the schematic and the amp, figure it yourself (like we would)

4) carry amp and schematic to a Tech, who will figure it himself.

[Jon Snell]

Move the neutral wire (maybe the live depending on how it is wired) from the Black/White tap to the brown.
That's it.

[nevetslab]

Here's the rest of the AC Mains Primary wiring & the power supply circuits:

[Helmholtz]

Line voltage & Blue 90 volts) is what you ultimately want to connect.

You surely meant Blue 0V.

[Jazz P Bass]

"You surely meant Blue 0V."
Yes!
I corrected the post.
I meant to hit 'shift 9'.

[J M Fahey]

Move the neutral wire (maybe the live depending on how it is wired) from the Black/White tap to the brown.
That's it.

Close but not enough.

He will *also* need to move the Tweed connection from T1 to T2, as indicated on the picture.

But since the picture is INCOMPLETE I´d like to see a bit more, to be safe.

Remember it´s an MB, "why make it simple when we can complicate it?"

In fact, the schematic on post 5 shows the proper connection as "export wiring",including T2

[Enzo]

And if you were to call Mesa, they just might be able to tell you, "Move the red wire to here and the green wire to there and then..."

[DaneZ]

Hi everyone. First off thank you so much for all of your contributions and I am indeed fortunate that you have taken the time to assist me with your knowledge and expertise.

I sincerely hope that this will help others in the future.

My apologies for the INCOMPLETE pictures and data to give you all an accurate visual of the problem.

Here is another pic and the following information.

The WHITE wire that is soldered under 0v is attached to the power cord plug socket.

The WHITE wire that is soldered under 100v is attached to the bottom of the Power on (Full or Tweed) Toggle switch at the front of the amp next to the Standby Toggle switch.

The BLUE wire that is soldered under 117v is attached to the top of the Power on (Full or Tweed) Toggle switch at the front of the amp next to the Standby Toggle switch.

Thank you all again.

Regards Dane Z

[DaneZ]

Done.

Thank you all again and I hope the following assists someone else if they require it.

I changed the fuse to 1.5A Slo Blo.

The WHITE wire that WAS soldered under 0v and is attached to the power cord plug socket was moved to the solder point under the BROWN 240V wire.

The WHITE wire that WAS soldered under 100v and is attached to the bottom of the Power on (Tweed) Toggle switch was moved to the solder point under the RED/BLK T2 wire.

The BLUE wire that WAS soldered under 117v and is attached to the top of the Power on (Full ) Toggle switch was moved to the solder point under the BLUE 0V wire.