Hi,
the diode beeper sound from my trusty FLUKE Series 70II had been getting r ather faint over time - the piezo element is attached to the back cover and connects to the main PCB via conductive rubber pads pressing on a couple o f solder blobs on its underside.
In the past, cleaning all the contact areas helped, but not that much.
So, a few weeks back I decided to hard wire the darn thing to the PCB with short runs of fine, Teflon coated wire. This worked like a charm as the two metal coated areas of the piezo element solder very nicely. Then I installed a new 9V battery ( Polaroid brand, heavy duty) and closed the meter up. Two weeks later the battery was near flat. Cursing cheap shit e Chinese batteries, I fitted another, this time an Alkaline type.
Two weeks later, it was nearly flat too, causing the battery icon to remain on.
When checked with another DMM, I found the battery drain was way high at 14 mA !! Also, the current draw hardly varied if I used a fresh 9V battery or the old one. Very odd.
I suspected a leaky tantalum cap across the battery, but there isn't one. T hen I removed the PCB from the case and the current went back to normal at
0.3mA. When I re-fitted the PCB, up it went again.WTF ?
You will not likely guess the cause so I will tell you.
When I hard wired the piezo element, I reversed the polarity of the connect ions to the PCB - such elements are not polarised, so it could not possibly matter.
But I neglected to disable the conductive rubber pads. The crossed over wir ing meant they were now both connected directly across the terminals feedin g the piezo element when the PCB was installed and pressing down on them.
Those terminals have about 5V DC across them when not beeping - enough to s end 14mA though the rubber.
... Phil