Marantz 1070 volume issue

Hey everyone, hope you're all well.

The issue I'm having is that whichever speaker is connected to the left channel is significantly louder than the one connected to the right. I have switched the speakers around and it stays with the left channel. I have also cleaned the potentiometers and connections inside the amp for the output channels to no effect. I'd appreciate some more ideas or a definite fix.

Thanks!

EDIT: the problem persists at low and high volumes

 

I would think that it needs to be re-capped, a bad capacitor in one channel will drop the volume significantly for that channel.

 

It has a balance control, no guarantee that the detent is actually at the center of volume. Same with the volume knob and even tone knobs, they are two independent potentiometers, without measuring the values produced by components, you can't know if they are still matching after years of wear. So measurement of the potentiometers would be one of the first things to follow up on.

Then as a technician, one can inject signals at different stages and measure the outputs to find the source of mismatch.

 

likely something to send it away for?

 

I would follow Harby's advice above first. You will need to have someone (unless you are handy.......I'm not) check the potentiometers, if that checks out ok then it would likely be a capacitor issue.

 

I have a multimeter, I'm going to attempt it myself. best guide you know of online?

 

You can get the service manual online, but it won't have distinct procedures for techniques learned in electronics school. You do want to unpower and unplug the device for a while before working on it to let capacitors discharge before testing passive components.

Since the system is stereo, you are comparing two channels, which gives you a distinct advantage. We assume one is operating correctly. You can check the resistance value between one channel of a potentiometer to ground or between the input and output, and compare it to the other side. Start with a stereo volume pot, observe the value going from 0 ohms to 100k ohms with logarithmic taper as you turn the knob and see the other channel has the same value.

If you can read a schematic, you can follow the signal chain, and probe the difference in AC value from a test tone, under operation. One touch or slip in the wrong spot, and poof, you've blown something up, though.

I am in favor of correctly diagnosing issues before repairing issues. Ever take your car in, and they replace parts that didn't fix the problem? That's a failure with logical diagnosis skills, and one shouldn't have to pay for another's incompetence in their trade.

Here's another post where a user cleaned out what they could see (repair?), and discusses a bit where one might find replacement parts: Marantz 1070 Parts

 

I have this exact same issue :-( Curious to know how your issue was resolved Rees? I bought this 1070 from its original owner and its been sitting in a (likely very filthy and moist) garage for the last 15 years. I brought it home (2,000 miles) and have cleaned it up (de-oxit inside on circuit boards and POTs) and it seems to be working well except that the right channel is quieter than the left. The volume / balance controls seem solid and smooth so I'm guessing its something like what Harby and Chazz are describing. This is my second 1070--my other one is working fine. The reason I mention this is that I believe the Left channel is operating properly based on what I get from both channels on my other unit. And since no one has ever done any work on this thing before I'm guessing that typical items that wear out (caps?) or what have you need replacing? I am handy enough to clean / adjust things, disassemble / reassemble, etc. But I'm not the guy you want taking a soldering gun to a circuit board :-/ I have a lot of respect for service technicians and so I am mostly looking to find out if someone could recommend someone in my area (shipping these things is ridiculously expensive). If replacing capacitors is somewhat straight-forward and parts available without much trouble then I have a guy that works on turntables that is likely skilled enough to do that--though I would more like having someone that can do the fine adjustments etc. too. Any advice, pointers, etc. will be greatly appreciated.

 

Just a quik update--I'm sure this will mean something to someone "in the know." The issue is seeming to diminish with time a bit. i.e. the right chennel seems to be "coming around some" this is after about an hour straight at 1/3rd volume level. Its alive! and getting better?

 

Probably a coupling capacitor somewhere in one channel. Easy to isolate and repair with experience and test equipment, difficult without. Your turntable guy might be able to do it if he has an oscilloscope and some idea of what goes on inside stereo equipment, but most TT work is more mechanical and this is electronics.

 

Thank you for the tip--I'll talk to my TT guy but I'm pretty sure this is out of his league--you're right about that--he's more about mechanics but I think he's going to school for electronics.