Connecting the Lar/Mar in a Bugera 1960

[tshodges]

Pot wired/mounted, 220K resistors pulled, V4-7 connected; where do I connect the other three wires?

[julkke]

The wires should lead to output tube pairs pin 5s, one to v5 and v4, one to v6 and v7. Take a look at a layout. Now, if the power tube sockets are on a pcb these wires are probably traces and you have to cut them.

[tshodges]

Which side of the 220k resistors do I connect the common wires?

[tshodges]

[tshodges]

Which side of the 220k resistors do I connect the bias feed?

[julkke]

I really can't tell from the pics, I'm sorry. The traces can't be seen very well.

[tshodges]

:/

[gloeidraad]

Hello,i hope i can help you.
The common wire from the potmeter goes to the common connection of the two 220k resistors.
And the other two wires goes to the other side of each connection where the resistors where.
When the amp is squeeling you have to reverse the two wires.
Hope this helps.
Good luck

Erik

[tshodges]

Thanks!

[gloeidraad]

Hello,a little correction,the common wire from the potmeter goes to the biasfeed, that is where the two 220k resistors are
connected to eachother.
There is actually no ground, you adjust the signal toward the bias when you lower the volume.
When the amp squeels, you have to reverse the two wiper wires.
And twist the wires!!!
Let me know when it works.

Erik

[gloeidraad]

One more thing,remove the output tubes and switch on the amp and check if there is bias at pin 5(+/- 40 volt negative)
If thats OK,switch off and place the output tubes back, and then look if it works

Erik

[julkke]

Yep there is no ground connection in this master, however the bias feed works kinda like ground here. You take the bias feed connection from where the 220k resistors are tied together and put the red and black wires from the other ends of where the 220k resistors were to the pot. From the pot wipers the wires go to pin 5 of each pair of output tubes as shown in the ppimv layout. Before firing up it is indeed wise to take out the power tubes and check that you have negative dc voltage at all of the pin 5s of the output tubes. If it checks out put power tubes in. If the amp squeals reverse the wires at pin 5s.


I hope this cleared it up.

[neikeel]

How it should be wired is pretty easy, it is working out where the components and traces are based on those pics and never having had one opened up in front of me before.
Do you have a numbered schematic for your version?

[SteadyEddie]

I thought the 1960 had a PPIMV?
What type is it? Is a Lar/Mar better?

[julkke]

I thought the 1960 had a PPIMV?
What type is it? Is a Lar/Mar better?

I believe it's the infinium version that has a ppimv, this is one of the older models which don't have. No idea what type it is in the infinium but I wouldn't be surprised if they just copied the larmar...