Buzz on left channel

[Tabaia]

Hi,

I turned on the mainline today.
Left channel now has a buzz in the signal.

What I have done:
1: Changed inputs - no change
2: unplugged input - no change
3: Changed headphone outputs - Balanced out has slightly less buzz
4: Plugged into different power out lets - no change
5: Listening without feeding audio into the unit I changed the volume pots - no change in buzz, it remains constant and no change in level.
6: Changing to high impedance increases the noise up a notch.
7: had a look through the the soldering underneath, nothing was immediately obvious to me.

Right Channel is completely silent.

What would the next step be?

 

[Paul Birkeland]

If you tap pretty hard on the top plate, does the buzz go away?

Typically something like this is just a solder joint that isn't 100%.

 

[Tabaia]

Did some tapping all around the top plate as well as gently lifting the whole unit and  tapping the whole unit on the  table. no change.

 

[Kris]

Did you try different headphones?

 

[Tabaia]

yes i did try different headphones

 

[Kris]

Try swapping tubes too just to rule that out.

 

[Tabaia]

Just swapped them - no change

 

[Paul Birkeland]

Can you report the IA, OA, and OB voltages on both of the high current C4S boards?

 

[Tabaia]

Here are the voltages
C4S Board A 
IA : 260.0
OA : 219.1
OB : 135.6
C4S Board B 
IA : 255.0
OA : 218.8
OB : 130

 

[Paul Birkeland]

Do you hear the same noise with nothing plugged into the RCA inputs?

 

[Tabaia]

Yes, the hum is consistent regardless of anything being plugged in or increases in the volume pots.
There is only a change when switching between low and high impedance, high increases the  hum.

 

[Thermioniclife]

Clean the tube pins and if you can clean the socket receptacle's. I believe Doc B has a video regarding this.

 

[Tabaia]

I removed and swapped the tubes, as far as the socket goes it should be ok as it is quite new.In anycase removing and resetting the tubes made no difference.
I think the issue may be elsewhere.
Thanks for the tip though, after looking at some other posts I gained some more knowledge on tube socket cleaning.

 

[Tabaia]

Just wanted to post these readings again.
What would the next problem solving step be?

Here are the voltages
C4S Board A
IA : 260.0
OA : 219.1
OB : 135.6
C4S Board B
IA : 255.0
OA : 218.8
OB : 130

 

[Paul Birkeland]

I would put a pair of inexpensive headphones on and run the amp flipped over, then poke around with a wooden chopstick.  Eventually you may find that poking a certain part of the circuit changes the noise you're hearing, and that can help you find loose connections.

 

[Tabaia]

Ah Yes, I had done that already but will give it another go.

 

[Tabaia]

I Presume the readings are fine?

 

[Paul Birkeland]

There isn't anything in your DC voltages that indicates a problem.

 

[Tabaia]

Hello Again,
Still trying to problem solve the buzzing.
Have again and quite meticulously while the amp is on and with headphones  gone through with a bamboo skewer and probe'd all wiring, listening for any changes but could not detect anything.

Also gently wiggled the transformers. Agin could not detect anything.

Kindly advise of the next step to take.

Many thanks

 

[Paul Birkeland]

Can you post build photos?  What kind of solder was used on the build?