My Crack is humming. [resolved]

[ideal.hat]

Hello.

I am dealing with a hum in my Crack 1.1 + Speedball (New Version set of 2x PCB’s)

The hum started soon after I finished the Speedball update.
The first thing I did was to disconnect the RCA cable but the hum was still there.

In the beginning is seemed to be related to the RCA jacks because I could see that if I jiggled a little bit with the RCA cables, I was able to get rid of the hum for few minutes.
Then I installed new tubes and then I notices that the hum was much louder, so I put in the stock tubes and same results = Louder hum.


Hum Description:
When the Volume pot is at Zero, I can hear the hum. It is louder in left channel.
When I turn the volume up, the hum gets louder.
It does not work anymore to jiggle with the RCA sockets, nothing seems to affect this hum.
I would shoot at that this hum is somewhere between 100-200Hz



This is what I have done so far:
I have swapped both tubes with another set I have.
I have replaced the RCA sockets.
I have made sure that ground it touching the plate. I needed to scrap of some pint in order to have clear contacts.
Pencil trick. I knocked all connectors and punched all cables. Nothing affected the hum..
I have re-soldered all connections.

Nothing has worked to get rid of this hum.

Here are my readings (With Speedball connected)
I believe that strange things are happening with A3, A4, A5 and B7, B8
T1   80,4   
T2   170,5   
T3   0   
T4   170   
T5   77,2   
T6   0   
T7   103,9   
T8   0   
T9   102,3   
T10   0   
T11   0   
T12   0   
T13   179   
T14   0   
T15   189,4   
T16      
T17      
T18   83,3   
T19   78   
T20   0   
T21   209   
T22        
A1   77,4   
A2   0   
A3   1,5   
A4   44,6   It took long time to go down to this number
A5   43,5   It took long time to go down to this number
A6   79,1   
A7   0   
A8   1,5   
A9   44,5   
B1   78,8   
B2   168,7   
B3   103,4   
B4   76,6   
B5   168,9   
B6   101,7   
B7   46,1   
B8   46,2   
      
Small PCB   
OA   79,6   
IA   167,2   
B-A/B   0   
IB   166,8   
OB   77,2   
      
Big PCB      
G   0   
OB   102,6   
B+   166,7   
OA   101,1   


Thanks.

[fullheadofnothing]

Your hum has to be entering before the volume control; either the source, cabling, or wires from the jacks to the potentiometer. If it was in the circuit, then the volume pot wouldn't affect it.

[Paul Birkeland]

A4   44,6   It took long time to go down to this number
A5   43,5   It took long time to go down to this number

On power transformer terminal number 4 (where the red and black twisted pair of wires connect and go to B7/B8), there's a black wire connected that grounds this winding.  The original kit had this wire going to terminal 22 or 14 (at the builder's discretion).  This wire isn't doing it's job in your kit.  Connecting power transformer terminal 4 to terminal 16U would be my recommendation for your particular issue. 

-PB

[ideal.hat]

On power transformer terminal number 4 (where the red and black twisted pair of wires connect and go to B7/B8), there's a black wire connected that grounds this winding.  The original kit had this wire going to terminal 22 or 14 (at the builder's discretion).  This wire isn't doing it's job in your kit.  Connecting power transformer terminal 4 to terminal 16U would be my recommendation for your particular issue. 

-PB

Hello Paul.

You were right.

Connecting the Transformer terminal 4 to 16U solved the issue.
My crack is now very close to be totally silent (Using Raytheon 6080) , but there is still a very,very low hum and it starts to get louder after I pass 12 o clock.
Is that normal?

My newly bought RCA 6AS7G is making some strange noises. I can see that if I tap the tube, the noises change (I should avoid touching the tubes while running, but Im just trying to figure this out).
I have also noticed that the noise change when I move the base of the RCA. I have cleaned the pins on the tube with alcohol.



Do you think this could be a broken RCA 6AS7G or that I have some issues with the socket?

[Paul Birkeland]

My crack is now very close to be totally silent (Using Raytheon 6080) , but there is still a very,very low hum and it starts to get louder after I pass 12 o clock.

I don't know what 12 o'clock means.  Is that the volume control all the way up?  Is the amp listenable at this volume level?  (See the Crack FAQ about this).

My newly bought RCA 6AS7G is making some strange noises. I can see that if I tap the tube, the noises change (I should avoid touching the tubes while running, but Im just trying to figure this out).
I have also noticed that the noise change when I move the base of the RCA. I have cleaned the pins on the tube with alcohol.

This is generally either an issue with the tube internally, pins that need to be cleaned, or a solder joint on or around the octal socket that isn't quite working properly.

[pingping]

Check that your transformer is tightened down

[ideal.hat]

I don't know what 12 o'clock means.  Is that the volume control all the way up?  Is the amp listenable at this volume level?  (See the Crack FAQ about this).
This is generally either an issue with the tube internally, pins that need to be cleaned, or a solder joint on or around the octal socket that isn't quite working properly.

Thanks for getting back to me.

"I don't know what 12 o'clock means.  Is that the volume control all the way up?  Is the amp listenable at this volume level?  (See the Crack FAQ about this)."

I realise that I have not been clear and just speaking in my own terms. What I mean is that when the Crack is at 0 volume, the volume pot it pointing towards 6 o'clock.
When the the volume pot is turned up to 50% it's at 12 o'clock. The crack is pretty loud at 50%, I am always under that volume. but when nothing is running, I can hear some noise comming in at 50% volume and it gets louder as I work my way upto 100% (I have been hoping the amplifier is dead silent at 100% volume)


"This is generally either an issue with the tube internally, pins that need to be cleaned, or a solder joint on or around the octal socket that isn't quite working properly."

I have contacted the British company that sold me the tube and they suspect its broken and they want me to send it back to them. The guy I spoke to was very nice and told me in full honest that the guy that want the main "valve" checker just passed away recently and they are dealing with some quality issues after that. for now, I will blame this on the new tube.

[ideal.hat]

Check that your transformer is tightened down

I will take a look at then when I come home from work. I will give you a feedback on it.

[Paul Birkeland]

I realise that I have not been clear and just speaking in my own terms. What I mean is that when the Crack is at 0 volume, the volume pot it pointing towards 6 o'clock.
When the the volume pot is turned up to 50% it's at 12 o'clock. The crack is pretty loud at 50%, I am always under that volume. but when nothing is running, I can hear some noise comming in at 50% volume and it gets louder as I work my way upto 100% (I have been hoping the amplifier is dead silent at 100% volume)

See FAQ #5
http://bottlehead.com/smf/index.php?topic=4295.0
We could throw feedback around the Crack circuit to calm the nerves of those who believe that it's important that there be absolutely no noise at any volume control position, but this does other things to the sound of the amplifier that we don't like.  Also, you have to remember that it's signal to noise ratio, and it is a ratio.  If you're going to let through so much signal that the amp woul be unbearably loud to listen to, you shouldn't be surprised that the noise floor has also come up.

[ideal.hat]

See FAQ #5
http://bottlehead.com/smf/index.php?topic=4295.0
We could throw feedback around the Crack circuit to calm the nerves of those who believe that it's important that there be absolutely no noise at any volume control position, but this does other things to the sound of the amplifier that we don't like.  Also, you have to remember that it's signal to noise ratio, and it is a ratio.  If you're going to let through so much signal that the amp woul be unbearably loud to listen to, you shouldn't be surprised that the noise floor has also come up.

My nerves have calm down now I have been trough the FAQ now and I am not so stressed about the background noise on high volumes.
I will only focus on listening volumes and do what is necessary to keep the noise floor low there.

My crack is pretty silent with the stock tubes.

I will RMA the new RCA 6AS7G today and lets see what I will get instead.

The treat can be closed.

Paul helped me with the ground connection. For that I am thankfull.