"Michael Black" wrote in message
xample.org...
On Mon, 22 Dec 2014, KenO wrote:

Received a nonworking GPX C971 Cassette/CD Boombox for repair learning
experience.

Used DVM to check Ohms on AC and DC connections Both were infinity for
power switch off and on.

Am guessing the problem is a blown fuse.

Checked the forum using keywords "GPX C971" got nothing.

Googled using keywords "GPX C971 schematic" also nothing.

Am sure that the the schematic is on the Internet so would be interested
in help finding it.

But what isn't working?

I've had boomboxes that wouldn't work without batteries. They were needed
to run the clock and remember the memories. I assumed they'd not be
needed when plugged into the wall, but that wasn't the case. Sometimes
they have a set of aa cells in there for that purpose, besides D cells
that aren't needed if powered off AC.

I recall the radio didn't work without the batteries, I can't remember
what else happened. But the radio is the easiest thing to check, and that
may be the problem. I recall not seeing anything on the LCD display until
I did put in batteries, but it's been a while.

Michael



All valid observations, but any kind of older boombox will likely have a
straightforward linear supply utilising a power transformer. The primary of
such is almost invariably connected straight across the power socket, and so
can be read on a meter set to ohms. The OP said that he had a reading of
infinity across the AC ...

Whilst there might be a separate fuse, this is often not the case,
protection being afforded by a thermal fuse buried in the primary. The on /
off switch is also never in the primary circuit. This is always either a
mechanical switch in the main low voltage supply rail, or a tactile switch
read by the system control micro, which then outputs a control signal to
turn on sleeping parts of the power supply.

If the unit uses a 'figure 8' AC socket, this is the first place to look. It
is extremely common for these to go bad jointed, often on just about every
pin. This can give the symptoms described, because not only is it the AC
input socket, it also has a switch that 'rolls over' when the plug is
inserted. This switch controls where the DC to run the set comes from i.e.
either from the secondary side of the AC power supply, or from the
batteries.

Arfa