Marantz 4270 DC offset and bias adjustment

The Donk! · 25th February 2008, 10:50 PM

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! · 26th February 2008, 07:50 PM

Anybody have a clue?

EchoWars · 27th February 2008, 11:45 AM

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! · 27th February 2008, 08:49 PM

Quote:

Originally posted by 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...

I just found a manual today. I ordered it.

EchoWars · 28th February 2008, 03:15 AM

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

The Donk! · 28th February 2008, 04:03 AM

Quote:

Originally posted by EchoWars
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 · 8th February 2010, 03:53 PM

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

25th February 2008, 10:50 PM	#1
The Donk! diyAudio Member Join Date: Feb 2008	Marantz 4270 DC offset and bias adjustment 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.

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26th February 2008, 07:50 PM	#2
The Donk! diyAudio Member Join Date: Feb 2008	Anybody have a clue?

27th February 2008, 11:45 AM	#3
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	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...

28th February 2008, 03:15 AM	#5
EchoWars diyAudio Member Join Date: Dec 2002 Location: Left of the Dial	Cool. Get 'er tweaked-up and let us know if you can hear an improvement.

8th February 2010, 03:53 PM	#7
aloutah diyAudio Member Join Date: Feb 2010	How much did it cost to do the repair? I have one of these with some issues.