EUROPEAN TO USA HELP 5213 MOSFET 100 Reverb Twin, 100W 2x12" combo

[bassforlife2007]

Hey New here in advance thank you for any replys!

I have A MARSHALL  5213 MOSFET 100 Reverb Twin, 100W 2x12" combo that Was left in my basement of my house when i purchased it! I bought a step up transformer (external) but would like to swap the transformer for a 110v vs the 240v. I uses the same 3 ground plug as usa but on the back of the amp states 240v  and the internal fuse is 2a for this as well, Wondering if any ones knows what transformer i need to make it 110v and besides swaping that and the fuse is thiere any other componets that need swapping?

O also it works with the step up on 220v but is noisy and the volume jumps from 0 to 100percent! randomly , the POTs are scratchy tho i think that is the issue what do you think!

Thanks Jeff

[J M Fahey]

Hi Bass.
You are talking two different problems here.
The fact it jumps randomly to different volume levels, scratchy pots and the like, means dirty/rusty/grimey pots , jacks and switches, normal on any old amp and even more if it was unused for a long ime in a damp environement.
You can clean everything with Deoxit or any similar product.
About the voltage conversion, do your homework, search for the schematic and post it here (or a link to it) and we'll guide you for that conversion, if possible.
Good luck.

[bassforlife2007]

Thanks for the reply! Sorry I didnt post it first I already got the schmatic here is the link
http://www.schematicheaven.com/marshallamps/mosfet_100reverbtwin_100w_5213.pdf

I will grab the cleaner thank you! , As far as the transformer more help would be great.

[Jack1962]

agreed it needs some seriously cleaning to start with , if you need a diagram for this amp go to http://www.schematicheaven.com there's one there .  However it is for the export not the U.K.

                                              Rock On

[bry melvin]

Using Hammonds "Design Guide for Rectifier Use" I come up with that you need a 70V CT transformer:

Bridge Rectifier...capacitor filter... So +50 -50 (according to the schematic) DC :

So 100 VDC/ 1.41 = 70

and you'd probably need about 250VA

Hopefully one of the super gurus here will check my math

[J M Fahey]

Hi Bass. Your schematic shows a code 789-66 power transformer, with 3 color identified secondary wires (Red/Black/Red) and unidentified (on the schematic) primary wires.
It also shows that they correspond to 2 ¿120V? primaries, in this cas in series.
Take a couple pictures of the transformer-to-mains wiring and redraw that part, showing wire colors. Maybe you are lucky.
If you have only two primary wires, you are stuck. You might replace the power transformer with a new, modern one.
Bry's math is good; the schematic suggests a 190VA transformer.
Good luck.

[bry melvin]

Thanks for the double check. JM

If the transformer has 4 primary wires, they'd be wired in parallel for Europe. So they'd need to be wired in Series as per the schematic.

If the transformer doesn't and needs to be replaced a hammond 167N70 would work...it's actually 280VA I misread earlier. the choices from Hammond seem to be 140VA (too small) or the 280

Of course other are other brands too

FWIW Mouser has 2 of the Hammonds 167N70s in stock.

[J M Fahey]

Hi Bry, 90% right this time.
The primaries, being 115 or 120V each , should be wired in parallel in the USA and in series in Europe. You must pay attention to the phase also.
Good luck.

[bry melvin]

ok sorry got confused there.  SO that would mean the schematic referred in earlier posts is in fact showing European wiring... and isn't the "export" version after all?

Sorry for the dyslexia.

FWIW that's one of the reasons I usually buy Hammonds...they have nice pictorial instructions for their products.

[bassforlife2007]

heres the links to the photos so you dont have to scroll over in the forum

The arrows and circled wires on the PCB are the wires coming from the transformer , let me know if this is suficent for pics

The current Transformer Manufacturer is DRAKE (its hard to read in image)
Thanks again for helping me out greatly apreciated

http://i815.photobucket.com/albums/zz78/bassforlife2007/IMG_1014.jpg

http://i815.photobucket.com/albums/zz78/bassforlife2007/IMG_1021.jpg

http://i815.photobucket.com/albums/zz78/bassforlife2007/IMG_1020.jpg

http://i815.photobucket.com/albums/zz78/bassforlife2007/IMG_1018.jpg

http://i815.photobucket.com/albums/zz78/bassforlife2007/IMG_1015.jpg

[bry melvin]

As far as I know the only wires you would need to change are at the top of the transformer The brown ones and a blue one

consider the pic #14 at the top of the transformer in this pic you have 4 connections

Lets call them 1 2 3 and 4 left to right

I THINK you need to remove the jumper from 2 and 3

place a jumper between 1 and 3
place a jumper between 2 and 4

change the fuse to a 3 amp

You Might want to wait for a second opinion from one of the experts though. I'm a musician that fixes her own not an amp tech.

[bassforlife2007]

So the transformer is capable of being used as 120 usa it has 2 120 rails? sorry if im mistaken i think thats what i gathered from your reply , please let me know

[J M Fahey]

Bry got it right again.
As "a picture is worth 1000 words", here go my 1000 words:

By the way, nice amp. They don't make them like these any more.

[bassforlife2007]

Wow this worked out good huh no need for a replacement transformer! a local tech looked at it and wanted to charge me 200 for a transformer I knew he was scamming!

as for the amp I was very happy to open it up and see 1987 since thats my year of birth so its as old as me. and not seeing surface mount was even more joyus!

I will solder those points pop in a new fuse and let ya know how i make out.

Do you know if the POTS would be sealed in 1987? do you recomend compressed air vs deoxt?

[Jack1962]

Try the replacement transformer for the Marshall MG100Dfx I believe it use's the same transformer .

                                             Rock On