its always somethin

Relax in southern comfort on the east bank of the Mississippi. You're just around the corner from Beale Street and Sun Records. Watch the ducks, throw back a few and tell us what's on your mind.
Post Reply
User avatar
JR.
Posts: 2243
Joined: Sat May 24, 2008 7:21 pm

its always somethin

Post by JR. » Mon Feb 05, 2018 2:15 pm

P1010247.JPG
Had some new drama while building drum tuners today...

The photo is showing the - end of the battery. The shiny spot at roughly 2 o'clock on the outer rim is where the battery spring contact pierced the plastic battery wrap. While I never inspected the batteries very closely apparently the metal casing of the battery is positive, with the negative electrode floating centered in the big end.

The spring with a sharp edge from the coiled wire apparently pierced the insulation and shorted the battery. The initial symptom was some extra distortion at the very LF end of the frequency scan, so apparently low battery voltage. Which I confirmed with a quick measurement across the 4 cell battery pack.

Then I noticed unusual heat coming from behind the top PCB. In over a decade of building these and probably hundreds of these exact batteries, this is a first.

Since one speaker sounded nastier than the other, I swapped the speaker and battery. FWIW the tuner, correctly completed the original scan and read the correct note (I have a lot of headroom engineered into the PS), but I suspect the shorted battery would have caused more mischief over time. :oops:

It looks like I have a new concern when assembling these, make sure the spring contact is centered. Only we can prevent house fires. :lol:

JR

User avatar
mediatechnology
Posts: 2974
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: its always somethin

Post by mediatechnology » Tue Feb 06, 2018 7:18 am

In one of my weather instruments using AA batteries the negative coiled spring gets pushed off-center by the battery. When I remove the battery the spring is hung in place and I have to flick it to get it to extend before installing the replacement battery. It looks just like all the other springs so I can't see what causes it.

I suppose its only a matter of time before that one shorts out.

Some time ago I posted a pic from Radio World of a reversed-polarity 9V. I can't remember if it was just the marking or it had the wrong type of snap connector installed.

Now if someone could just explain why the DC leakage current from my kitchen faucet to earth ground reverses polarity when the water is turned on. It's a current mirror!

......Or maybe a current "sink." :lol:
(rimshot)
"We have grown to love our captors and demonize those that try to lead us to freedom."

User avatar
JR.
Posts: 2243
Joined: Sat May 24, 2008 7:21 pm

Re: its always somethin

Post by JR. » Wed Feb 07, 2018 2:40 pm

mediatechnology wrote:
Tue Feb 06, 2018 7:18 am


Now if someone could just explain why the DC leakage current from my kitchen faucet to earth ground reverses polarity when the water is turned on. It's a current mirror!

......Or maybe a current "sink." :lol:
(rimshot)
There is apparently some weirdness from metal content in the sundry faucet parts.. flowing water may change the metal sections dominating the voltage/current.

or in other words, I don't know. :lol:

JR

Post Reply

Who is online

Users browsing this forum: No registered users and 4 guests