Mesa Boogie 20/20 power amp - convert to 220/240 Volts

[fearless]

Hi - I wonder if anyone can help me. I want to see how easy it is to convert a US domestic model 20/20 from 117 to 220/240 mains input?

I've done some searching and apparenlty if it is a universal transformer, it just needs re-wiring inside. as it has muliple taps. I'd probaly get a tech to do it. But some Mesas apparently have "US dometic only" transformers which don't have the extra taps.

I can't open the amp up to check - I haven't bought it yet! Just want to buy a US one if I can convert it for Australia without too much trouble/cost.

I do already have a stepdown transfomer, but don't want to lug it around if I can avoid it. Weight saving is part of the whole reason for getting 20/20 in the first place.

Any help would be appreciated.

 

[Snoopy551]

Following the schematic,
You can change the wiring to have an input voltage for 220V compatibility.

For 120v Black and Brown wires are connected together.
and
Black/yellow and Brown/yellow wires are connected together.

For 220V
remove the connection of Brown and Black/yellow
and connect Brown and black yellow together. put a protection on this connection.

The schematic has been found on internet.
check if you see the same colors in you mesa 20.

Good luck
Steph

 

[scoot_001]

Hi.

I'm in hte same boat with my Triaxis and have had two quotes.

Soundworks (Ringwood - Melb, Vic) said anywhere from $100 - $300 - depending on the type of mounting and power supply it has.
The only other authorised boogie repairer quoted over $600 - they didn't want to do it as the importer gives them grief if they help out folk that bring these into the country on the cheap. .

Good luck - let me know how you go.

 

[Snoopy551]

It seems the same thing of mesa 20.

But i do not have any schematic of power supply schematic.

 

[Snoopy551]

i Scoot

A do not have a schematic.
BUt email or better call at mesa boogie.
I am sure it will figure it out.

In my triaxis i have 3 wires. Black, gray and white,
is not clear, how to mix.

I hope there are only 2 or 3 solder and unsolder to do.
$50 box maximum.

Let me know, if you solve the problem

 

[crane]

There's a 20/20 schematic availlable on the Yahoo Triaxis group, with the PS wiring diagram for 110-220v.

 

[fearless]

Well I bought a 20/20, tested it first using an isolating tansformer, then did the conversion. I got the details from the jemsite forum.

BUT - it worked OK for a while, jus few minutes use at low volume, and tonight I had the chance to crank it and it blew a fuse. Now the jemsite instructions said change for a 110V 2A fuse to a 250V 1A fuse. Which makes sense.

So I'm worried I've stuffed something up.

An ideas? I was only using one channel (with the other right down of course) and about 1/3 volume. There are no bad smells from it so I guess the fuse has done its job. If I try again with another fuse using the other channel, is that fairly safe?

 

[Snoopy551]

HI Fearless

Could you send the link of the instruction???

first, It should be easier to check.

Thanks

 

[fearless]

Can't find the link again but here are the photos:

 

[fearless]

Schematic shortly. Downloaded from here...

http://www.bnv-gz.de/~ooehmann/schematics/mb/20_20.zip

 

[fearless]

 

[fearless]

The other things I was told to to do were:
1. Change the 2A fuse to a 250V 1a fuse (twice the voltage, half the amps - makes sense) - but if anyone has an "original" 240V model, I'd be interested to know if it is actually this rating
2. Change the metal oxide varistor (MOV). Mesa wanted to charge $20 for this $1 component, and they won't tell you the specs. So I checked with a tech and was told 275v 40J would be typical, so went with that. It is much smaller thatn the original, but I believe an MOV is a non-critical compnent, there as extra circuit protection in case of extreme voltage spikes.

Mark, or anyone else - if you have any advice I'd sure appreciate it. I notice in the schematic that there are symbols for other componenents in th 240V power supply. Caps, I think? No values though. Since this seems to have worked for others I did not think they were critical but might be more "power conditioning".

Since I never really cranked it up before foing the mod, I guess a possibility is that it has an unrealted fault.

 

[Snoopy551]

HI Fearless

I suggest, put a 1AMP fuse and at low power, check the supply as good.

 

[fearless]

OK, so if I understand right - same fuse type and just play with the volume at a low level. I'll do that tomorrow and report back. Thanks

 

[fearless]

No problem at volume on other channel. Assume therefore not on the power supply side.

 

[Snoopy551]

I expect the problem is on the power supply.

When you play a high volume, more power are needed from the PS(power supply),

Are you using a Slow blow fuse or lag time fuse? (like recommended)
Do you have a ampmeter?
if yes, to make a measurement on AC at the input.(Like to replace the power switch)
and check the current when you are playing.

If it doesn't work, write to technical mesa boogie,
i am sure it going to help you?

 

[fearless]

I expect the problem is on the power supply.

When you play a high volume, more power are needed from the PS(power supply),

Are you using a Slow blow fuse or lag time fuse? (like recommended)
Do you have a ampmeter?
if yes, to make a measurement on AC at the input.(Like to replace the power switch)
and check the current when you are playing.

,
i am sure it going to help you?

I was using a "slo-blo" fuse initially when it first blew, and for the next time I didn't have one handy so used a regular 1A fuse. I have some more slow blow fuses now, so planning to change it back.

I don't have an ammeter to put in line, but do have an AC current clamp. I think I can borrow one though.

If it doesn't work, write to technical mesa boogie i am sure it going to help you?

Not quite sure what you're saying there..a typo, methinks - were you saying Mesa technical would be helpful?

 

[Snoopy551]

i will send you a private message or email.

 

[Snoopy551]

http://www.tubeampdoctor.com/produc...d=143&osCsid=c2e32c91f126526bd931d5258167f1b3
http://www.tubeampdoctor.com/product_info.php?cPath=27_47&products_id=144

Hi Fearless

I am sure, you can use one of the transformer.

Snoopy

 

[fearless]

Thanks Snoopy. Turns out the conversion is fine. I might have a power tube on the way out, but hammered it for hours on Friday with no issues. Getting new tube set just in case.

BTW I did the deep mode and made it switchable. Not sure whether I like it better with/without, but I can switch one channel at a time which is pretty handy.