On Fri, 21 Oct 2022 19:41:26 -0500, John Crane
<john_crane_59@yahoo.com> wrote:
Bought one in excellent shape.
Worked great for about a month, then developed a buzzing background
noise in the audio - but you can still hear the weather reports. Just
annoying.
It's been sitting on a shelf the whole time. And 9V battery powered.
I tried replacing all the electrolytic caps, but no go. In fact, the
buzz is slightly louder.
Any ideas as to what could cause this?
Does the buzzing follow the volume control? In other words, does
turning the volume up and down change both the weather report AND the buzzing, or is the buzzing a constant level?
The problem might a new source of EMI (electromagnetic interference).
Try moving the cube around the house and see if the buzzing gets
stronger near some new electronic or motorized equipment. Also try
moving the cub outside and down the road to see if it goes away with distance.
I once had a weather cube. I found that nearly dead 9V batteries
would cause the audio state to "motorboat". It was easier to replace
the battery than the fix the problem, so I never troubleshot it down
to the failed component. I suspect you might have a similar problem
if you're using a rechargeable LiIon 9V battery, some of which only
produce 7.2VDC. If you have a new 9V alkaline battery, try it.
Bought one in excellent shape.
Worked great for about a month, then developed a buzzing background
noise in the audio - but you can still hear the weather reports. Just >annoying.
It's been sitting on a shelf the whole time. And 9V battery powered.
I tried replacing all the electrolytic caps, but no go. In fact, the
buzz is slightly louder.
Any ideas as to what could cause this?
The buzzing follows the volume control, it's not constant.
Moving it around the house doesn't affect the buzzing. It stays at a
constant level. And no new equipment came online in the house since it's
been in use.
My battery was a Duracell alkaline at 8.59V. I replaced it with another >Duracell at 9.19V. No change in the buzzing.
Really a strange problem. I'd suspect a bad connection somewhere, but
the problem just appeared slowly as it was used on a shelf. There was
no movement, or jarring involved that could have knocked something
loose. And there is a lot of wax poured over the components -
presumably to keep the little coils fixed in shape. I thought the >electrolytics finally gave out, as it's a vintage one with faux wood
grained sides. Maybe 70's - 80's era.
It's a 12-181b.
As luck would have it, it came with a little paper schematic and user's
guide tucked in the battery compartment....attaching a jpg of it.
On 10/22/22 9:24 PM, Jeff Liebermann wrote:
On Fri, 21 Oct 2022 23:01:20 -0500, John Crane
<john_crane_59@yahoo.com> wrote:
The buzzing follows the volume control, it's not constant.
OK. So it's in the receiver section, before the volume control.
Is the model number 12-174 or 12-181b?
Any chance you have a schematic or a URL with a schematic? I couldn't
find anything using Google Image search. Everything seems to point to
radio-reference.com, which has some RS information, but nothing on the
weather cube.
Moving it around the house doesn't affect the buzzing. It stays at a
constant level. And no new equipment came online in the house since it's >>> been in use.
OK. That eliminates an EMI/RFI source. You're probably on the right
track looking for something wrong with the cube.
My battery was a Duracell alkaline at 8.59V. I replaced it with another >>> Duracell at 9.19V. No change in the buzzing.
So much for the almost dead battery theory.
Really a strange problem. I'd suspect a bad connection somewhere, but
the problem just appeared slowly as it was used on a shelf. There was
no movement, or jarring involved that could have knocked something
loose. And there is a lot of wax poured over the components -
presumably to keep the little coils fixed in shape. I thought the
electrolytics finally gave out, as it's a vintage one with faux wood
grained sides. Maybe 70's - 80's era.
The buzzing sound is something oscillating at an audio rate. Lots of
things in the RF and low level audio section could do that. Most
likely is a power supply bypass cap. I suggest poking around the PCB
with an oscilloscope looking for oscillation, but that's difficult
without a schematic.
Try poking around the PCB with your finger. If you find an area where
you finger changes the noise, investigate that area for bad parts,
residual flux or bad components. Maybe an alcohol and brush cleaning.
A dead electrolytic is a possibility. Instead of removing and testing
the caps, find a similar value cap and temporarily connect it across
each electrolytics on the PCB, one at a time. Soldering is best but
just holding it on the solder pads is sufficient. I like to put a
sharp point on the capacitor leads (with a diagonal wire cutter) in
order to punch through the protective goo and wax on the PCB.
It's a 12-181b.
As luck would have it, it came with a little paper schematic and user's
guide tucked in the battery compartment....attaching a jpg of it.
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