scheme CODE 25-50 incl. repair hints

[J Hoeve]

The charts of the CODE 25 and 50 are too big to upload them here, send an email to me, pe1rfe@outlook.com. and I'll send it to you. Also state in which language you want it.


Repair description MARSHALL CODE 25 AND CODE 50.

1. Connect the PSU to the mains using a 230V , 100W light bulb in series.
This protects various parts in the event of a shutdown in the power supply.
When closed, the lamp will light up, and the current will be limited, you can then also
usually still measure some voltages, or with complete closure of a part
nothing. This way you will be helped on your way to what is wrong .
This circuit can of course be used with any power supply or amplifier.
If the lamp is blinking, it indicates that the power supply is "hitting", which usually indicates
on a closure in the secondary part of the PSU.

2. Disconnect the wires from the PSU to the amplifier . yellow and white wire ,
this is the U1 voltage. The PSU must be loaded, for proper control.

DUMMY RESISTANCE.

CODE 25.
For a PSU of CODE 25 take 3 resistors of 47 R 10 W , connect them in parallel.
That gives a resistance of 15.6 R , the supply voltage of the CODE 25 U1 is about 16 V .

CODE 50.
With the CODE 50 you take here for 3 resistors of 68 R 10 W, you also place these parallel to each other.
Now the resistance is 22.6 R , U1 of the CODE 50 is about 21 V.

3. I have encountered several times in the power supplies that the OPTO 1 (dual optocoupler) was faulty.
If you hear a loud "clack" in the Speaker when you turn on the power button, it's almost
always broken. It is also possible that this error manifests itself by turning the volume potentiometer, the sound
falls away comes back after a few seconds and can then be very deformed, cannot be adjusted properly.
NB !
In this case ALWAYS disconnect the wires from the PSU from the amplifier and place the dummy.
The U1 voltage can then rise much too high, and damage the power amplifier and other circuits.

I have also often come across that after the error with the optocoupler, the PRESET settings of the various tone
species was disrupted, and that it was too loud and reproduced the sound with a lot of distortion.
So all set up again.

4. Parts that I have often replaced :
OPTO 1 = mct 6 dual optocoupler
DZ 1 = 18 sc zener
DZ 3 = 12 v zener
C13 (code 25)
C 15 ( code 50 )
C 16 = 220 uF 25 V (code 25)
C16 = 330uF 35V (code 50)
Q 1 = spp08n80c
D8 = mcc s2150 schottky rectifier
D7a = dss6-150as schottky rectifier
D1 = mcc sk810 schottky rectifier

 

[Tatzmann]

Easy Way:



But thanks for your info, some guys actually
like wasting time and money

 

[Turcobein]

The charts of the CODE 25 and 50 are too big to upload them here, send an email to me, pe1rfe@outlook.com. and I'll send it to you. Also state in which language you want it.


Repair description MARSHALL CODE 25 AND CODE 50.

1. Connect the PSU to the mains using a 230V , 100W light bulb in series.
This protects various parts in the event of a shutdown in the power supply.
When closed, the lamp will light up, and the current will be limited, you can then also
usually still measure some voltages, or with complete closure of a part
nothing. This way you will be helped on your way to what is wrong .
This circuit can of course be used with any power supply or amplifier.
If the lamp is blinking, it indicates that the power supply is "hitting", which usually indicates
on a closure in the secondary part of the PSU.

2. Disconnect the wires from the PSU to the amplifier . yellow and white wire ,
this is the U1 voltage. The PSU must be loaded, for proper control.

DUMMY RESISTANCE.

CODE 25.
For a PSU of CODE 25 take 3 resistors of 47 R 10 W , connect them in parallel.
That gives a resistance of 15.6 R , the supply voltage of the CODE 25 U1 is about 16 V .

CODE 50.
With the CODE 50 you take here for 3 resistors of 68 R 10 W, you also place these parallel to each other.
Now the resistance is 22.6 R , U1 of the CODE 50 is about 21 V.

3. I have encountered several times in the power supplies that the OPTO 1 (dual optocoupler) was faulty.
If you hear a loud "clack" in the Speaker when you turn on the power button, it's almost
always broken. It is also possible that this error manifests itself by turning the volume potentiometer, the sound
falls away comes back after a few seconds and can then be very deformed, cannot be adjusted properly.
NB !
In this case ALWAYS disconnect the wires from the PSU from the amplifier and place the dummy.
The U1 voltage can then rise much too high, and damage the power amplifier and other circuits.

I have also often come across that after the error with the optocoupler, the PRESET settings of the various tone
species was disrupted, and that it was too loud and reproduced the sound with a lot of distortion.
So all set up again.

4. Parts that I have often replaced :
OPTO 1 = mct 6 dual optocoupler
DZ 1 = 18 sc zener
DZ 3 = 12 v zener
C13 (code 25)
C 15 ( code 50 )
C 16 = 220 uF 25 V (code 25)
C16 = 330uF 35V (code 50)
Q 1 = spp08n80c
D8 = mcc s2150 schottky rectifier
D7a = dss6-150as schottky rectifier
D1 = mcc sk810 schottky rectifier

Can you tell me the value for C13 in Code 50? I´m found it in short

 

[J Hoeve]

C13 = 15 nF

 

[PelliX]

Repair description MARSHALL CODE 25 AND CODE 50.

1. Connect the PSU to the mains using a 230V , 100W light bulb in series.

Inside it's just an SMPS with a half bridge rectifier, though, no? Wait, lemme email you... I want to see this!

 

[sstudio]

Hi.
I have a marshall code25 amp.
Can I have a part number of the potentiometer for master volume control?

 

[PelliX]

Hi.
I have a marshall code25 amp.
Can I have a part number of the potentiometer for master volume control?

Should be printed on the back of the pot, no? A500K, or something like that?

 

[welead_amy]

has anyone successfully solved the psu code50 problem?

 

[welead_amy]

can anyone share psu code50 diagram. please email me welead_amy@yahoo.com

 

[PelliX]

has anyone successfully solved the psu code50 problem?

to the MF.

What, pray tell, is "the psu code50 problem"? It's just a SMPS and a fairly simple one at that. You could probably replace it with anything that supplies a regulated ~15-20V DC, taking the power handling into consideration and any low voltage supply (though I can't recall seeing one straight from the PSU off the top of my head, I think it does some regulation and smoothing on the mainboard).

 

[welead_amy]

to the MF.

What, pray tell, is "the psu code50 problem"? It's just a SMPS and a fairly simple one at that. You could probably replace it with anything that supplies a regulated ~15-20V DC, taking the power handling into consideration and any low voltage supply (though I can't recall seeing one straight from the PSU off the top of my head, I think it does some regulation and smoothing on the mainboard).

I've researched it.. only if there is a diagram to connect the wire to the psu it would be better. I'm afraid I'll connect it wrong, and I'm not good at electronics

 

[PelliX]

I've researched it.. only if there is a diagram to connect the wire to the psu it would be better. I'm afraid I'll connect it wrong, and I'm not good at electronics

Let's start with the basics - and don't read this in a condescending tone, it's just helpful to know what we're dealing with here.

1) What leads you to believe the power supply is malfunctioning? What I tend to ask people with problems are two simple questions to start out with; "what's it doing that it shouldn't?" and "what's it not doing that it should?".

2) Do you have a multimeter to check the output voltage of the current power supply? If so, what is it putting out?

3) Is there any optical damage, burn marks, ripped traces, melted components, physical breakage? Gut shots are very much encouraged here.

4) What do you mean by 'not good at electronics'? This ranges from "I might not feel comfortable designing the control and protection circuitry for a nuclear power plant without a review by a peer" to "I have no clue what the difference is between a resistor and a capacitor".

 

[fitz]

I've researched it.. only if there is a diagram to connect the wire to the psu it would be better. I'm afraid I'll connect it wrong, and I'm not good at electronics

If you're just looking for pics of the PSU connections, I gutted 2 CODE50's to make speakers cabs....
They were 2 different versions.
Here's some pics of the guts.

 

[welead_amy]

Let's start with the basics - and don't read this in a condescending tone, it's just helpful to know what we're dealing with here.

1) What leads you to believe the power supply is malfunctioning? What I tend to ask people with problems are two simple questions to start out with; "what's it doing that it shouldn't?" and "what's it not doing that it should?".

2) Do you have a multimeter to check the output voltage of the current power supply? If so, what is it putting out?

3) Is there any optical damage, burn marks, ripped traces, melted components, physical breakage? Gut shots are very much encouraged here.

4) What do you mean by 'not good at electronics'? This ranges from "I might not feel comfortable designing the control and protection circuitry for a nuclear power plant without a review by a peer" to "I have no clue what the difference is between a resistor and a capacitor".

3) Is there any optical damage, burn marks, ripped traces, melted components, physical breakage? Gut shots are very much encouraged here.

This is what happened..yes no 3

 

[PelliX]

3) Is there any optical damage, burn marks, ripped traces, melted components, physical breakage? Gut shots are very much encouraged here.

This is what happened..yes no 3

What?

1) What leads you to believe the power supply is malfunctioning? What I tend to ask people with problems are two simple questions to start out with; "what's it doing that it shouldn't?" and "what's it not doing that it should?".

yes

2) Do you have a multimeter to check the output voltage of the current power supply? If so, what is it putting out?

no

3) Is there any optical damage, burn marks, ripped traces, melted components, physical breakage? Gut shots are very much encouraged here.

3

 

[fitz]

Or was the answer:
Yes, #3?
(optical damage, burn marks, ripped traces, melted components, physical breakage?)

Gut shots are very much encouraged here.

This might help clarify...

 

[GansoGuitar]

Dear all, new member here.

Please, anyone have this schematic available? I have one Code 25 with power supply fault in my workbenck now.

Greetings from Brazil.

 

[PelliX]

Dear all, new member here.

Please, anyone have this schematic available? I have one Code 25 with power supply fault in my workbenck now.

Greetings from Brazil.

No schematic available as far as I know. The PSU however is a pretty simple standard switcher. Just take a look in Youtube for videos about troubleshooting/fixing SMPS's (Switched Mode Power Supply). Pro tip: build a lightbulb limiter before you get started.