Marantz 4270 DC offset and bias adjustment

[The Donk!]

I just got done completely rebuilding a 4270.

I have 8 new finals and all new caps in the amp boards.

Does anyone know how to adjust the bias and DC offset?

Thanks.

 

[The Donk!]

Anybody have a clue?

 

[EchoWars]

Is it not worth buying the manual to find out?

Honestly, if I had the manual, I'd scan the page for ya. But it's not like a huge investment...

 

[The Donk!]

Is it not worth buying the manual to find out?

Honestly, if I had the manual, I'd scan the page for ya. But it's not like a huge investment...

I just found a manual today. I ordered it.

 

[EchoWars]

Cool. Get 'er tweaked-up and let us know if you can hear an improvement.

 

[The Donk!]

Cool. Get 'er tweaked-up and let us know if you can hear an improvement.

Well, I honestly couldn't say. The left channel was all jacked up. It passed signal. Just wasn't being amplified.

After I replaced about 30 parts, for good measure. It just didn't quite sound right.

I actually just finished replacing everything on the amp boards accept for trimmer pots and output coils today.

She sounds great now.

The DC offset is fine.

I haven't checked the bias, because I don't know how.

It's not obvious to me. I see a few ways it could be done.

But....

This is not mine. I am doing this for a friend of a friend, who can't really pay to have it done. Nice guy though.

So, I'd really hate to break it again.

Because I "donated" all the new parts. And can't really do it again!

I can tell you though.

This is one nice unit.

And thanks for the responses Echo.

 

[aloutah]

How much did it cost to do the repair? I have one of these with some issues.