CODE 50 Power failure


I have, or should I say, HAD a Marshall CODE 50 which after 20 months of service decided to quit following a POWER SUPPLY failure.  I took it to an electrical repairer for diagnosis and found out, through Marshall Australia and UK that the power supply is not replaceable because it has been suspended.  No parts available.  That means I now have an amp that is unfixable and never will be, even with an aftert-market power supply - which, according to Marshall cannot be retro-fitted.  What a fantastic waste of money that exercise was, and I have zero warranty fall-back.  Has anyone else had the same problem?  Kev

asked 01 Apr 2019 at 03:01 AM

Kev Lawlor (1)
Hey Kev,
Did you get ya another amp? I had the same problem, got a replacement amp. Then had another problem with the LED screen blanking out on me, got another amp. Warranty says 5 years on parts, 3 on labor and Marshall has stood by that for me. I'm in the US but think that should make any difference.
Chris W.
- Chris Warren 17 Mar 2020 at 07:17 AM
Answers: 3


Hello Kev,

I have forwarded your first e-mail to our distrubutor in Australia Electric Factory who are looking into your case and will be in touch with you with a solution. So please wait to hear from them and the situation will be resolved, if you have any issues please contact us at


Kind Regards

Marshall Support

answered 01 Apr 2019 at 07:37 AM

I have got the same problem, how can I have my marshall fixed?

kind regards
Ermanno Sartori from Venice (italy)
- Sartori Ermanno 07 Nov 2019 at 11:45 AM
Hi Ermanno,

Thank you for your comment, sorry you seem to be having this issue, I would recommend contacting your dealer for advice on a repair as the warranty is with the shop

Marshall Support
- Marshall 07 Nov 2019 at 11:50 AM


I am an electronic technician and I solved the problem  replacing power supply with one of  24V 5A  and one 24/3.3V step down dc/dc converter. Fixed with less than 10$ .

regards  Ermanno Sartori 

edited 21 Mar 2020 at 09:41 AM

Sartori Ermanno (1)

answered 18 Nov 2019 at 01:29 PM

Sartori Ermanno (1)
Hi Sartori,

Please email with this request.

Marshall Support
- Marshall 18 Nov 2019 at 01:43 PM


Hi Ermanno


I have the same issue. any chance you could let me have the 5 pin header and main yello/white power specs and pinout. Thanks

answered 28 Sep 2020 at 12:31 PM

tony scragg
Hi Tony,
I can tell you about yellow/white wires.....following from power supply card: there's an electrolytic capacitor in parallel, follow polarities (24Vcc).
about 5 pin header, only two wires are important near you will see an 8 pins ic, is a regulator, his output voltage is 3.3V, the 5 pins header uses this voltage for supply all digital logics. my amp is abroad now so I can't open it to tell you how connect your wires, but you can easy find the pins following the pc-board... I should have in a corner of my home a paper with something as ink-dirth if I'll find I'll post to you. All you have to do is make attention and follow the circuit, Better if you use an ohm-meter.

- Sartori Ermanno 30 Sep 2020 at 02:16 PM
Ermanno, thank you for the additional information. I had a good look at the PSU board. I had already confirmed yellow=+24v White=0v. The 8 pin chip you referred to is an RT8299 regulator. Pin 3 is the output and pin 4 is ground. I traced these to the 5 pin header and they are connected in 2 pairs with one pin not connected. The black wire on my ribbon cable and the pin next to it are +3.3v and the following 2 pins 0v. Connected it up to my bench power supplies and hey it all sprang into life :-) I just need to find or build a PSU now. I'm guessing the 24v will need to be about 2-3A. The 3.3v measured at about 0.5A on my bench PSU. - tony scragg 30 Sep 2020 at 04:25 PM
That's ok Tony. You can use an dc-dc step down converter from 24V to 3.3V so only one 24V power supply is needed. ( 0V is common ) or, if on board regulator is ok ( as I belive) You can keep this powering 24V immediately before RT8299 chip so use 5 pin header (please check voltages before connecting other electronics. Have good play using your amp :-). Wishes from Venice. Ermanno - Sartori Ermanno 01 Oct 2020 at 06:25 AM
A 75W 24v SMPSU and buck step down regulator for the 3.3v are now ordered. Thanks for the tip to check voltages before connecting. I will update the post when , hopefully the amp fully working. - tony scragg 02 Oct 2020 at 11:04 AM
After a bit of further work I have discovered that if the 3.3v and 24v power supplies share a common 0v then there is some sort of ground loop created, resulting in a fairly high pitched noise on the audio output even with no input present. This is totally eliminated if electrically isolated power supplies are used. The two 0v are through the main board. - tony scragg 06 Oct 2020 at 01:50 PM
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