Markbass Little Mark II

[Fabrizio]

Hi , I am very new to this Forum and I hope to find some help with this amp I have.
I Have a Markbass Little Mark II that is switching on no problem , preamp section works , DI works but I don t get any signal to the speaker.
I checked cables etc, Speakon connection, jack connection everything ok but no signal.
Before I had a few times where I had this issue , everything switch on fine but no output from the speaker.
So by switching on and off the amp I would manage eventually to get the signal back.
Then one day nothing....
I checked also the connections of the speakon to the main board and it appears to be ok.
No burnt components.

Anyone with some good advice ?

Thank you very much

[Jazz P Bass]

Is there an output relay that is used on this amp?

[nickb]

I saw one of these once with very similar symptoms. One of the connections to the master pot was broken. A bit of a long shot but it's easy enough to check

To answer Jazz's Q: Yes, there is a relay.

Fabrizo: You should be able to hear the relay engage a short time after power up. If it does, the power amp is probably OK. What is the level is your technical ability? What test equipment to you have?


>>> Schematic <<<

[Fabrizio]

I saw one of these once with very similar symptoms. One of the connections to the master pot was broken. A bit of a long shot but it's easy enough to check

To answer Jazz's Q: Yes, there is a relay.

Fabrizo: You should be able to hear the relay engage a short time after power up. If it does, the power amp is probably OK. What is the level is your technical ability? What test equipment to you have?


>>> Schematic <<<

yes i can hear a relay engaging
i have multimeter

[Fabrizio]

I have replaced caps and transistors on amps many times but I have no experience on those kind of class D amps, it does look difficult...

[nosaj]

I have replaced caps and transistors on amps many times but I have no experience on those kind of class D amps, it does look difficult...

I had one a month ago similar problem except sound was intermittant. Turned out the speaker jack was internally fractured a new switchcraft jack and it was in business.

nosaj

[Fabrizio]

no i tried different speakers already and changed cables and use the neutrick combo or the jack socket ,same problem

[nickb]

I have replaced caps and transistors on amps many times but I have no experience on those kind of class D amps, it does look difficult...

Well it's class AB so no worries there The power supply is a switcher but it sounds like it's working anyway. This box uses a lot of surface mount parts which can present a new challenge if you are not used to them.

First, plug your guitar into the effects return and see if you get an output. If that works, simply patch from the effects send to the effects return and see what happens.

Also, does the tuner output work?

[nosaj]

no i tried different speakers already and changed cables and use the neutrick combo or the jack socket ,same problem

ok what about the master volume connector. the MV pot has a connector that goes to the mainboard is it connected?

nosaj

[Fabrizio]

Hi Nick,
I already disassembled the amp pcb boards and i think you found the culprit straight away!! the master pot is a loose on the connections. i think needs soldering but if i remember with those pots you need to be careful when soldering

[Fabrizio]

Hi Nick and Nosaj,

I wanted to thank you very much for the advice : I managed to change the pot and everything is working fine now !!!
I am disappointed with mark bass for using such cheap type pots, I was expecting better quality parts on their expensive products,

Anyway I am sorted now and THANKS AGAIN!!!