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Bottlehead Kits => Crack => Topic started by: nate craig on March 08, 2015, 12:26:29 PM

Title: Crack Speedball Hum. Need Help, Pls
Post by: nate craig on March 08, 2015, 12:26:29 PM

Hi everyone,

I just upgraded to Speedball, I have found a hum on the left and I haven't been able to sort it cause.
I checked the solder joint, visually and with meter, and they all seem fine.
I tried different tubes, rca cables and source, all with the same result.

Does anyone have any other ideas as to where I can search or do?
I am new to building electronics, so any help will be appreciated.



 

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: Paul Birkeland on March 08, 2015, 04:06:59 PM

I would start by providing us with voltage measurements, especially those that differ from the manual.

-PB

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: nate craig on March 14, 2015, 01:25:49 PM

Hi PB:
None of the readings were to far off from the manual, all within 4-5 volts from the manual. The only odd one was that terminals 6 and 10 did not have static readings. The value fluctuated between -2 and +4.

I checked the continuity of all of the joints they are all fine as well.

Any other places or items that I can check that would help guide you to the cause? It also seems that the hum is on both sides, not as I had originally thought.

Thanks, Craig

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: Paul Birkeland on March 15, 2015, 07:39:42 AM

I would then double check that all your 220uF 250V capacitors are well connected.  If one comes loose, the amplifier will hum.

-PB

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: nate craig on March 15, 2015, 08:00:35 AM

Paul,

The solder seems really solid on all three.
Do you think re-soldering them will improve?

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: Paul Birkeland on March 15, 2015, 08:02:35 AM

Twist and pull on them with your fingers (with the amp off).  If one is loose, it will move more than it should.

-PB

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: nate craig on March 15, 2015, 10:33:54 AM

Hi Paul,

Yes, that's what I did, and they are all tight. Is there any other possible source of the hum?

Craig

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: Paul Birkeland on March 15, 2015, 11:23:40 AM

Hum with no cables plugged into the Crack and the volume control all the way down is almost always a loose connection.  When you upgraded the amp, you may have disturbed what was a loose connection, but one that was operating regardless until it was moved.

I would suggest triple checking all your work, and reheating all of the solder joints in the amplifier, just to be sure.

-PB

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: nate craig on March 23, 2015, 03:29:04 PM

Paul,

I notice that the noise goes away and comes back if I touch the top of the input tube (RCA12AU7 Clear)
I know it's not the tube it self because I tested input that came with the kit and got the same hum.
I re-soldered as many of the joints on the socket as I could reach without removing the SpeedBall kit.
Do you think is there anything else to do with that socket before I remove the SpeedBall kit?

Thanks
Craig

Title: Re: Crack Speedball Hum. Need Help, Pls
Post by: Paul Birkeland on March 23, 2015, 03:53:51 PM

Quote from: theboyfrombluesea on March 23, 2015, 03:29:04 PM

I notice that the noise goes away and comes back if I touch the top of the input tube (RCA12AU7 Clear)

That generally indicates a loose connection around the 9 pin socket or accompanying terminal strip, or perhaps a bad ground connection between the chassis plate and the IEC socket.

This is very unlikely to be an issue with the actual Speedball itself.  You may find that the hum stays if you remove it.

-PB