Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: lbs on January 03, 2017, 02:00:21 PM

Title: static in right ear and humming [resolved]
Post by: lbs on January 03, 2017, 02:00:21 PM

I've been having some issues with my crack making noise.
The right channel makes a constant static noise. Doesn't matter what volume the potentiometer is at but the static varies in volume.
Also if I turn the volume above ~50% there is a buzzing sound but the sound does get louder the more I turn up the volume. but it's barely audible if a source is connected to it

I've checked all my numbers three or four times following the instructions on the manual and they all read within limits.
I changed the tubes out
re-soldered every connection and did the chopstick test
tried plugging it into different outlets
none of that made a difference.

I know the problem is with the amp, tried different sources and headphones.

The only two things I've replaced on the amp from the stock parts, apart from the tubes are the TRS jack and the potentiometer. the problem started  after around the time I replaced the potentiometer so I switched it back out with the original but it didn't fixed the issue. Tried switching to the original jack as well.

I'm thinking one of the parts went bad but I'm not sure what else to do to locate the bad component.

Thanks in advance for your help.  :)

Title: Re: static in right ear and humming
Post by: Paul Birkeland on January 04, 2017, 07:59:05 AM

Can you post some photos of your build?  Did you paint both sides of the chassis?

Title: Re: static in right ear and humming
Post by: lbs on January 04, 2017, 11:53:13 AM

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2F4oVof7J.jpg&hash=24b86fc82b4f6d51efac4aeee3746a17c4ea8abb)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FBxD19BU.jpg&hash=cedad853acdb5299616c499a6ca53e3f6dd6d8bc)

(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Fpp51ZWN.jpg&hash=c52ce09bc603eeb374691d8859d04d62c77e9e1c)


the wiring is a bit messy at the moment from re-soldering stuff
The chassis is not painted at all

Title: Re: static in right ear and humming
Post by: Paul Birkeland on January 05, 2017, 01:41:08 PM

Just to clarify, if a component fails, this is will be revealed in the voltage checks.  What you need to do is to put on an inexpensive pair of headphones, then take a wood chopstick and start poking around the circuit until you find the solder joint that modifies the noise behavior you're experiencing, then reheat all associated solder joints (after the voltage has bled off of course).

-PB

Title: Re: static in right ear and humming
Post by: lbs on January 05, 2017, 06:20:21 PM

tried it, tried it again, still the same problem.


So if all the numbers are good it's can not be a problem with the component?

Title: Re: static in right ear and humming
Post by: Doc B. on January 06, 2017, 05:46:01 AM

Try jumpering out the output of the right channel of the pot to ground. You would do this by connecting a clip lead between the upper center pot terminal where the red wire that connects to 12AU7 pin 7 is attached, and the upper black wire terminal on the pot, right beside it. That will take the pot out of the equation. If the static stops you know it's the pot (or something ahead of it) that is causing the problem.

I'm suggesting this because of your comment that the problem seemed to start about the time the pot was changed out, and that the static level changes with the volume setting. The pot or connections to the pot may have been stressed in the process of changing them out.

Title: Re: static in right ear and humming
Post by: lbs on January 08, 2017, 05:29:55 PM

I've tried what you suggested and it didn't seem to solve the problem.

Title: Re: static in right ear and humming
Post by: Doc B. on January 08, 2017, 07:00:03 PM

You might try cleaning the tube pins, particularly the 12AU7 pins.

Title: Re: static in right ear and humming
Post by: lbs on January 08, 2017, 08:03:56 PM

tried putting the tube in and out a bunch of times (recommended way of cleaning the pins from what I've read) but still having the problem.  :(

Title: Re: static in right ear and humming
Post by: lbs on January 17, 2017, 07:40:45 PM

I also tried changing out the 9pin socket but still having the same problem.

I've reflowed all the joints and doing the chopstick test doesn't make anything better or worse.
Also, re-did the resistance and voltage checks, no problems there.

Title: Re: static in right ear and humming
Post by: Paul Birkeland on January 18, 2017, 09:17:45 AM

What voltages do you have at T1 and T7?

Title: Re: static in right ear and humming
Post by: lbs on January 18, 2017, 09:23:35 AM

T1= 95

T7= 113.2

Title: Re: static in right ear and humming
Post by: Paul Birkeland on January 18, 2017, 09:33:29 AM

Can you confirm that the jumper that connects the two lugs with black wires on the pot is still in place? 

Title: Re: static in right ear and humming
Post by: lbs on January 18, 2017, 09:34:55 AM

yes it's still there.

Title: Re: static in right ear and humming
Post by: Paul Birkeland on January 18, 2017, 09:35:41 AM

The next step is to remove the red and white wires that leave terminals 1 and 5 respectively, then switch them.   See if the noise stays put in the right channel, or moves to the left.

-PB

Title: Re: static in right ear and humming
Post by: lbs on January 20, 2017, 10:25:41 AM

I had the crack turned on for a full day(ish) and the sound disappeared.

So problem solved!

Thanks for the help.