Mainline, Channel imbalance [resolved]

[elgringo81]

I am having issues with the volume controls on my Mainline.

The volume is higher on the right channel.
There is channel imbalance on all settings unless I set the Coarse volume to 0db. then it seems to become even.

If I set the Coarse to 0db and fine to 7.5db then the left channel is silent but sound is still coming through the right channel.

Does someone know what might be causing this?

 

[Paul Birkeland]

There is channel imbalance on all settings unless I set the Coarse volume to 0db. then it seems to become even.

This would make me suspect that you have an improperly installed resistor on the coarse switch.  With the fine control at 0dB at the coarse control at 0dB, what is the resistance to ground from each output (lower) lug on the coarse switch?

If I set the Coarse to 0db and fine to 7.5db then the left channel is silent but sound is still coming through the right channel.

This is likely an inconsistency between the resistor values at the -7.5dB position on the fine attenuator switch.

 

[elgringo81]

Coarse Volume set to 0db gives the following resistance reading.
lower lug closer to back 17,2kOhm
Lower lug closer to front 17,7kOhm



"This is likely an inconsistency between the resistor values at the -7.5dB position on the fine attenuator switch."
-I will look closer into this and report back in few minutes.

 

[elgringo81]

This is likely an inconsistency between the resistor values at the -7.5dB position on the fine attenuator switch.
- Could you be so kind to guide me on how to troubleshoot this?

 

[Paul Birkeland]

Coarse Volume set to 0db gives the following resistance reading.
lower lug closer to back 17,2kOhm
Lower lug closer to front 17,7kOhm

Is this also with the fine control set to 0dB (I am guessing not based on your numbers)

 

[Paul Birkeland]

This is likely an inconsistency between the resistor values at the -7.5dB position on the fine attenuator switch.
- Could you be so kind to guide me on how to troubleshoot this?

With the fine switch on any position other than -7.5dB, check the resistance from ground to the lug for each -7.5dB resistor.  These are the 6.65K resistors.  You can verify where they go by looking in the manual.

 

[elgringo81]

With the fine switch on any position other than -7.5dB, check the resistance from ground to the lug for each -7.5dB resistor.  These are the 6.65K resistors.  You can verify where they go by looking in the manual.

Thanks. That seems to be terminal 12 and the reading is = 7.21K , Fine is set to -3.0db.

 

[Paul Birkeland]

Let's try this:

Let me know each of these 4 resistances.

 

[elgringo81]

Let's try this:

Let me know each of these 4 resistances.

Here you go. I did put Fine to 0db as instructed.

 

[elgringo81]

It also seems strange that if I put the volume to MAX on the Mainline and the computer source to 100% volume, its not "that" loud. It is louder then I would like to listen to, but its not like my Crack that would have blown my head clean off.

 

[Paul Birkeland]

I should also check to be sure you have nothing plugged into the inputs when you're making these measurements.

The 15K reading is just plain wrong.  With the fine switch at 0dB, then the series string of resistors on the coarse switch can be measured.  There is about 25,000 ohms of resistance here.

I would strongly suggest measuring each resistor on each switch to be sure they are all in the correct spot.  I do not believe that they are.

 

[elgringo81]

I should also check to be sure you have nothing plugged into the inputs when you're making these measurements.

The 15K reading is just plain wrong.  With the fine switch at 0dB, then the series string of resistors on the coarse switch can be measured.  There is about 25,000 ohms of resistance here.

I would strongly suggest measuring each resistor on each switch to be sure they are all in the correct spot.  I do not believe that they are.

I am afraid that my measurements are all over the place. If you take a look at my latest attached picture, I have different values that I gave to you earlier.
I am an unexperienced beginner with a cheap multi meter. Can this picture tell us something?

PS: I am using ground on Terminal 7 when I take these measurements.

 

[Paul Birkeland]

Terminal 7 is a good ground to use.  Can you post some close up photos of your attenuator?

It should be very, very easy for a cheap meter to read proper resistance values between ground and all the fine resistors when the fine switch is at 0.

 

[elgringo81]

Terminal 7 is a good ground to use.  Can you post some close up photos of your attenuator?

It should be very, very easy for a cheap meter to read proper resistance values between ground and all the fine resistors when the fine switch is at 0.

Yes, its most likely a mistake on my site. But I took good care to use the resistors accordingly to the manual and the paper that the resistors came on with their resistance and also model number. I though to my self that its best to try not to mess this up because its not going to be so fun to troubleshoot

Here are the pictures of the attenuators. Let me know if you would like me to make more pictures.

Please not that there is a loose white wire  below and between terminal 1 and 2 on the Coarse attenuator. I have fixed that now.

 

[Paul Birkeland]

The solder joints at 6 and 8 might be part of the problem.

The white wire leaving the coarse attenuator is not soldered at the attenuator.

Of the resistor values that I can read, they look to be in the correct places.

-PB

 

[elgringo81]

The solder joints at 6 and 8 might be part of the problem.

The white wire leaving the coarse attenuator is not soldered at the attenuator.

Of the resistor values that I can read, they look to be in the correct places.

-PB

I have re-soldered 6 and 8
Also soldered the loose, white wire between 1-2 on the coarse attenuator.

Unfortunately, the problem is still there.

 

[elgringo81]

I have gone over each and every connector on both attenuators, cleaned up the tin and carefully re-soldered all off them, along with the 4x lower lugs.
This has not resolved the problem, there is still a channel imbalance unless I turn the Coarse Dial to 0dB.
With coarse dial set to 0dB, I can use the source volume to go from quiet to loud, without any channel imbalance.. It sounds very good..
Fine dial does not seem to be affected.

 

[Paul Birkeland]

I would suggest borrowing a meter that can more consistently read resistance values so we can continue debugging this issue.

 

[elgringo81]

Hello Paul.

I have resolved this problem.

Red wire coming from lower back lug on fine attenuator was incorrectly connected to lower front lug on coarse attenuator. !!It should have been connected to terminal 7 on coarse instead. Page 43 in the manual.!!

After I corrected this, the channels are totally balanced.

Thank you very much for all the help.

 

[Paul Birkeland]

Ah, that explains the odd behavior your were getting, good catch!