Bottlehead Forum

Bottlehead Kits => Crack => Topic started by: 12AU7-6SN7 on April 25, 2019, 08:39:18 AM

Title: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on April 25, 2019, 08:39:18 AM: The resistance check and voltage checks ok... the pot will make a scratchy noise around 8 o clock on the dial and buzzes and cuts the output volume a little, all in the left channel... if I go just above or just below the problem position of the pot it works fine. I reflowed some solder joints and it improved but I canâ€™t get it eliminated.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: Paul Birkeland on April 25, 2019, 10:37:56 AM: Can you post some photos of the pot and the area around it?

-PB
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on April 25, 2019, 11:44:51 AM: A little embarrassed of my substandard work

http://imgur.com/a/n5reCL3

No shorts on those wires or anything from what I can tell.. amp sounds beautiful everywhere but 8-8:30 on the dial.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: Paul Birkeland on April 25, 2019, 02:04:30 PM: The lower ground lug (black wires) on the volume pot looks like it might be a problem.

If you are using a small soldering iron (under 35 watts), I'd spend $5-10 on a 40-50 watt iron so you can really get those joints hot.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on April 25, 2019, 04:23:05 PM: Iâ€™ve got a really nice soldering iron station. My pop was a tech and it was his.

Iâ€™ll try redoing those ground lug joints tomorrow and see if it helps the issue... might just be the pot itself, weâ€™ll see... enjoying the music right now... this thing makes these ZMFs sing!
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: Paul Birkeland on April 25, 2019, 04:43:31 PM: If you have a station, be sure the temperature is turned all the way up.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on April 25, 2019, 05:27:13 PM: If soldering â€œstationâ€ means it is adjustable, I guess I had the wrong terminology. Itâ€™s a decent quality single temp (as far as I can tell) Weller with a base power unit and stand. Temp isnâ€™t a problem, I may have just done a crappy job there. I think the pic looks worse than it is, since it was shiny... the iron is at another location right now, so Iâ€™ll take the amp over there in the morning and see if it fixes it or not.

Thanks for your help Paul.

Edit: I think it is a 60 watt unit.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on April 26, 2019, 07:14:39 AM: Quote from: Paul Birkeland on April 25, 2019, 02:04:30 PM
The lower ground lug (black wires) on the volume pot looks like it might be a problem.

If you are using a small soldering iron (under 35 watts), I'd spend $5-10 on a 40-50 watt iron so you can really get those joints hot.

The actual solder joint on that lug was beautiful and shiny. I redid it anyway to no effect, along with the others on the pot. Still scratches at the one narrow spot on the dial.

Itâ€™ll do for now since it works perfectly otherwise, and I hope the new alps blue velvet should fix the problem when it arrives next month.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: Doc B. on April 26, 2019, 07:27:17 AM: Try exercising the pot.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on April 26, 2019, 07:54:58 AM: Quote from: Doc B. on April 26, 2019, 07:27:17 AM
Try exercising the pot.

Did that, also tried some chemtronics cleaner/water displacement/lubrication spray my pop used to use at work on potentiometers. Didnâ€™t work either.
Title: Re: Finished crack kit, potentiometer makes buzz in left channel at certain position
Post by: 12AU7-6SN7 on May 05, 2019, 08:41:30 AM: Alps pot fixed the issue. Good grooves time.