Help with info on Markbass little Mark 250 Blackline.

[Chimike]

Could someone with a Mark Bass Little Mark 250 please look inside their amp, and note down the values, voltage and orientation of the Capacitors

C5 and C6 , located close to the output Transistors . ( or does anyone have a circuit diag ? )

PLEASE only do this if you are competent and safe to do so , make sure the amp is unplugged , and do NOT poke inside .

The Caps should be clearly visible to a knowledgeable person .

Thanks ,

Mike

[Mediocre Polymath]

I have one of these amps, and I've had the cover off a few times to replace failed/crackly pots in the preamp board. 

 

I'll pop the cover off and take some pictures when I get a moment. These would be the big electrolytic, yes?

[Chimike]

Thanks,

Electrolytic's, Yes . Clearly marked on PCB C5 and C6.

[Mediocre Polymath]

So, I can't get any particularly clear pictures because the flash is bouncing off the other cables and components, but they're both marked as 100uF, 63v, and (I think) rated to 105C, though I can't get a clear look at the last part. 

 

 The person who assembled my amp was very generous with the rubbery fixing compound, so I had to scrape some of that away to see the PCB labels. 

 

Here's the C6 orientation (negative to the right when looking from the front of the amp)

And the C5 orientation (negative towards the front)

and a fuzzy image of the markings, just to confirm I'm not making this up. 

 

[Chimike]

That's Amazing,

Great,

Thank You.

I'll get them ordered up, together with the 4 220uf 200v caps in the power supply section that were stressed.

My friend who owns the amp said it was still functioning , hard to believe , but worth a go . C5 and  C6 had exploded, and are completely unrecognisable.

Best Wishes,

Mike

 

[Chimike]

Thank you !

Parts arrived from Farnell , and all fitted yesterday.

So far, so good ! Sounding great to me.

One thing I noticed was the voltage setting link is set on the middle position , 220v . ( middle of PCB )

Would you be willing to check your amp see which position your link is on. There is another position, next to it, with 120/240 written on it . Is your link there ?

There is also a large link at the side of the PCB , that is NOT fitted.

Best Wishes,

Mike.

[Mediocre Polymath]

3 hours ago, Chimike said:

Thank you !

Parts arrived from Farnell , and all fitted yesterday.

So far, so good ! Sounding great to me.

One thing I noticed was the voltage setting link is set on the middle position , 220v . ( middle of PCB )

Would you be willing to check your amp see which position your link is on. There is another position, next to it, with 120/240 written on it . Is your link there ?

There is also a large link at the side of the PCB , that is NOT fitted.

Best Wishes,

Mike.

I'll have a look in the morning. 

[Mediocre Polymath]

On 16/08/2025 at 18:19, Chimike said:

Thank you !

Parts arrived from Farnell , and all fitted yesterday.

So far, so good ! Sounding great to me.

One thing I noticed was the voltage setting link is set on the middle position , 220v . ( middle of PCB )

Would you be willing to check your amp see which position your link is on. There is another position, next to it, with 120/240 written on it . Is your link there ?

There is also a large link at the side of the PCB , that is NOT fitted.

Best Wishes,

Mike.

Hi there. Sorry I completely forgot about this. Here's the voltage selector, looks to be on 120/240 for mine. 

[Chimike]

Great, Thanks for your help.

Link corrected , testing fine, Result .

BTW ,you'll get to an age one day when you forget...... that you forget ! Then it doesn't bother you anymore !

Don't ask me how I know this !

Best Wishes, 

And thanks again for going out of your way to help.

Mike