Crack w/cycling hum

timbro52 · 1079

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Offline timbro52

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on: January 17, 2019, 08:31:11 AM
Hope someone can help me out!

So here’s the story, I’ll try to keep it short. Bought a Crack in 2010, assembled it and had issues getting it to power up. Got side tracked…(life) fast forward to last week.

My Stereomour’s power switch gave up the ghost after 8 years, not bad for a little piece of plastic. So I order a new one and popped it in. Great, that worked!
So I thought to myself, it’s time to tackle the Crack and find out where I messed up.

Did my due diligence and found the issue, a disconnected wire and bad soldering. Did the resistance check, all good. Fired it up and the tubes glowed beautifully. Did my voltage tests and all was well until I got to terminal 20. I got a zero reading and the manual says 206 VDC. So I checked terminal 21and I got 200 VDC. My first though was that maybe there was an error in manual. So I checked the forum and found an article about corrections, unfortunately the link was no longer active.

I decided to proceed and check the TRS jack voltage. All good there.
I felt relatively confidant that I wasn’t gonna blow anything up so I connected my source and spent the next 3 hours in sonic heaven!

So here’s the problem, this morning I fired up the Crack and after 10-15 seconds there’s a repeating hum about every .5 seconds, hum…hum…hum… very even, both sides of the cans.

Any assistance will be greatly appreciated!

Thanks,
Tim

Tim Darby


Offline Doc B.

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Reply #1 on: January 17, 2019, 08:39:09 AM
Two possibilities come to mind.

First possibility is outside interference like your cell phone, an appliance like a refrigerator, a wi-fi router, etc. Try turning those things off and see if it goes away. Sometimes trying a different outlet on another circuit in your house can help.

Second is a film cap got nicked by hot soldering iron and is discharging. Inspect the caps, including the underside you might not see from just a quick peek, for a melted spot. This is not as likely since you mention that it is in both channels.
« Last Edit: January 17, 2019, 08:40:53 AM by Doc B. »

Dan "Doc B." Schmalle
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Bottlehead Corp.


Offline Paul Birkeland

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Reply #2 on: January 17, 2019, 09:35:40 AM
a powerline Ethernet kit will also make a ticking sound over your powerline that can get into your gear.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline timbro52

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Reply #3 on: January 17, 2019, 09:47:33 AM
Thanks Doc,
You were right on crouton! The wall wart for my cordless phone was the cause the hum. Moved it to another circuit and presto, dead silent!

Thanks again Doc!

Love Bottlehead!
I’ve got a bunch
S.E.X. with circuit upgrade
Crack (soon to add Speedball upgrade)
Early Stereomour running Belle Klipsch
Seduction Phono Preamp

Tim Darby