Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => Amplifier Discussion => Topic started by: pinkjimiphoton on February 03, 2020, 09:00:05 PM

Title: Marshall 5203 220-117v mod?
Post by: pinkjimiphoton on February 03, 2020, 09:00:05 PM
hi peeps,
long time lurker, first post i think...
i have one of these amps
(https://drtube.com/schematics/marshall/5203.gif)
i'm hoping to pick up, but just realized its a canadian model set up for 220v, and i live in the usa where its 117v
(give or take)... looking at the schematic, it looks like i should be able to just move a couple wires on the power transformer to choose, and maybe change the fuse value to a slightly higher one..
but not sure looking at it, which way would this be implemented?
sorry if a dumb question, but it looks kinda like they jumper two parts of the power transformer together... would i just use one half of the pt primary? or do i need to remove something?
i'm a fair hand with a fuzzbox, but this is pretty much my first real rodeo with this kind of thing so i appreciate any advice i can get. thanks so much!
Title: Re: Marshall 5203 220-117v mod?
Post by: Enzo on February 03, 2020, 10:33:55 PM
There are two 120v primaries.  For 240v we wire them in series.  For 120v, we remove the series jumper, and use two jumpers to connect the tops together and then the bottoms together of the two primaries.  Puts them in parallel.
Title: Re: Marshall 5203 220-117v mod?
Post by: pinkjimiphoton on February 04, 2020, 12:49:31 AM
beautiful. thank you, enzo!! exactly what i needed to know.
have an awesome day, mate!
Title: Re: Marshall 5203 220-117v mod?
Post by: Jazz P Bass on February 04, 2020, 11:57:18 AM
So here is a pic of a 220 volt wiring.
Call the Blue wire tap #1.
#1 & 2 are one winding.
#4 & 6 are another winding.
For 220 V ac input the two windings are in series. (tap #2 & 4)
For 110 Vac input the coils should be in parallel.
So wire #1 to #4 and #2 to #6 .
Title: Re: Marshall 5203 220-117v mod?
Post by: g1 on February 04, 2020, 01:25:23 PM
Just for the record, voltage in Canada is same as USA.   ;)
Fuse values are both shown, 1A slow for North America, 500mA slow for UK.
Title: Re: Marshall 5203 220-117v mod?
Post by: pinkjimiphoton on February 05, 2020, 09:19:37 PM
thanks guys!
i won the auction for cheap, look forward to resurrecting the beast!
to me, this is the best series of amps marshall ever made, tonally, and i've owned plexis and 800's. all the tone without the earbleed glass. love 'em!
Title: Re: Marshall 5203 220-117v mod?
Post by: pinkjimiphoton on February 12, 2020, 06:00:21 PM
hi guys,
just checking in... amp arrived today, seems to be intact mostly <g>
gotta busted pot, so gonna throw it on the bench and fire it up. it looks like it has a normal
110v plug with it, so i may get off lucky with this, but thanks to your help, should be good.
i will post back how i make out.
again, thanks!
Title: Re: Marshall 5203 220-117v mod?
Post by: pinkjimiphoton on February 13, 2020, 06:39:48 PM
turned out already set up for 110v. very groovy! pretty good shape. had to graft a new volume pot in and caig it, and replaced all the electros... amp was marked 88, so i figured i should. fired right up, sounds boss.

thanks for the support guys. ya'll rock!