Marantz 2275 Left Channel very low

[Mca1310]

This is the challenge I'm facing today with my 2275. I have a very low volume on the left channel (compared to right) both on speakers and headphones. However (surprisingly) this applies only on FM Stereo (mono doesn't work if we select the left channel but does if we select the right one). This is the outcome of my tests



Where do you suggest I start my investigations?

Many thanks all for your fantastic support!

 

[rBuckner]

I'd ignore the AM issue while trying to solve the FM issue. That is if you're going to at all!

I'd be printing out the part of the schematic that is the FM stereo multiplex board and the parts layout. An oscilloscope would be ideal. But being the brave guy, I'd be using a clip lead if I didn't have a scope and shorting like points from each channel together to see how far back from the end it does NOT make the levels equal to try and pinpoint it. This is a dangerous method and may blow up stuff whether or not you slip with the clip lead ends. By clip lead i mean with mini grabbers on the ends, not brutish alligator clips.

 

[Mca1310]

Thanks Bukner, you're announcing me hard time during Christmas ...

 

[ocdecio]

If you are getting good stereo strenght, I'd look at these transistors that sit right after the discriminator. It looks to me as a sziklai pair (very high gain amplifier) for each side.

 

[Mca1310]

Thanks, you mean H304,305,306,307 right? If I read it right they feed the dolby sections (PC01 and Dolby FM)

 

[ocdecio]

Thanks, you mean H304,305,306,307 right? If I read it right they feed the dolby sections (PC01 and Dolby FM)

Correct. Or you can check the signal in and out of them and see if they differ on both sides.

 

[Mca1310]

it looks like I'll be having quite a busy xMas. I read in another post that removing the P300 is quite complex. All inputs are suggesting a component to replace on the P300 which won't be a funny moment

 

[ocdecio]

it looks like I'll be having quite a busy xMas. I read in another post that removing the P300 is quite complex. All inputs are suggesting a component to replace on the P300 which won't be a funny moment

I never removed it and I would never advise anyone to do it. There are a couple of wires that may need to be disconnected (I unsolder the pins) so you can swivel it, access is tight but by no means impossible.

 

[Mca1310]

but how did you do to dissolder components without removing the P300? on the bottom of P300 is a real jungle of cables and P400 is also in the way

 

[ocdecio]

As far as I know that's not where P300 is. Here's a picture of one of the 2275s I restored showing one of the wires I was disconnecting to swivel it and another showing it totally standing up with full access to the foil side..

 

[Mca1310]

The picture I posted is from a couple of years ago when i recapped but looking at service manual i'm pretty sure it should be there. Said that I hope I'm wrong because your pictures look much better

 

[ocdecio]

Here's P300 on your picture. You may be thinking of PS01 which has the Dolby FM switch.

 

[Mca1310]

right and when you look at the bottom you have the jungle i was referring to (top left corner). to be honest I don't remember where PS01 is. What I remember is that PE01 is in the top center of the bottom. Anyway I'll have to figure out when I will open it. Point is that i need to focus on P300 and don't even think to a simpler solution like cleaning the Stereo/mono button...