Hello Guys.
I have a Marshall MB series B150 bass amp combo.
The classic channel is not working. There is an ECC83 tube in the preamp circuit.
Any idea what to look for?
Thanks in advance.
P.S.: I cannot find the schematic anywhere.
I have a Marshall MB series B150 bass amp combo.
The classic channel is not working. There is an ECC83 tube in the preamp circuit.
Any idea what to look for?
Thanks in advance.
P.S.: I cannot find the schematic anywhere.
Then first clean all the switches and pots. Swap some tubes around.
If none of these make a difference, start looking for bad connections.
If none of these make a difference, start looking for bad connections.
Thanks Rayma. I figured out that the 12AX7 tube was bad. I put in another one and voilà, it woks again.
Well, I got the amp working, but when I plug a set of headphones into the jack, it sounds kind of crappy, no hights, plenty of mids, no low end.
And when using the CD IN jack (right next to the headphone jack), it is even more pronounced.
I'm aware that you cannot expect a 15" full range speaker to sound as good as a hifi system. But from a build in designated headphone amp?
When I took out the preamp pcb, I noticed a pair of transistors TR41 & TR42, both J111. With the pcb disconnected and out of the chassis, TRs still soldered in place, they show 20 ohms between gate and source. I don't know if this is ok.
There may be other issues with that pcb...
And when using the CD IN jack (right next to the headphone jack), it is even more pronounced.
I'm aware that you cannot expect a 15" full range speaker to sound as good as a hifi system. But from a build in designated headphone amp?
When I took out the preamp pcb, I noticed a pair of transistors TR41 & TR42, both J111. With the pcb disconnected and out of the chassis, TRs still soldered in place, they show 20 ohms between gate and source. I don't know if this is ok.
There may be other issues with that pcb...