I was given a Hercules XPS 2.140 Slim speaker system. The owner purchased it
new from Amazon and it never worked. It sat around longer than the return
period so I inherited it. The problem is that the 16 volt 1.4A power adapter
is not working. I cracked open the box and could not find any obvious
faults. In circuit, the 68uF 400V filter cap charges to the peak line
voltage but that's about all that is happening. I cannot measure any
oscillation at the MOSFET. I removed the MOSFET from the circuit and did the
quick DMM check where you put some voltage on the gate and drain and then
check the resistance between the drain and source. That test passed. The D-S
resistance went down to two ohms.

I removed the switching transformer and took these measurements:
Primary winding that goes to the MOSFET: 0.3 ohms DC.
Then I used my ESR meter on the primary windings and it measured 32 ohms.
There is another primary winding (at least it's on the same side of the
transformer as the winding that goes to the MOSFET and I think it feeds back
to the controller) that measures:
0.4 ohms DC
The ESR meter measures open circuit.
I used my Bob Parker LOPT tester and it actually lit up all the lights when
applied to these windings.

The secondary measure 0.4 ohms DC and 7.3 ohms with an ESR meter.

I was wondering if anyone can figure out if these measurements mean anything
or is there a better method to test this.

Thanks for your replies.
--
David Farber
Los Osos, CA

David Farber wrote:

I was given a Hercules XPS 2.140 Slim speaker system. The owner purchased it
new from Amazon and it never worked. It sat around longer than the return
period so I inherited it. The problem is that the 16 volt 1.4A power adapter
is not working. I cracked open the box and could not find any obvious
faults. In circuit, the 68uF 400V filter cap charges to the peak line
voltage but that's about all that is happening. I cannot measure any
oscillation at the MOSFET. I removed the MOSFET from the circuit and did the
quick DMM check where you put some voltage on the gate and drain and then
check the resistance between the drain and source. That test passed. The D-S
resistance went down to two ohms.

I removed the switching transformer and took these measurements:
Primary winding that goes to the MOSFET: 0.3 ohms DC.
Then I used my ESR meter on the primary windings and it measured 32 ohms.
There is another primary winding (at least it's on the same side of the
transformer as the winding that goes to the MOSFET and I think it feeds back
to the controller) that measures:
0.4 ohms DC
The ESR meter measures open circuit.
I used my Bob Parker LOPT tester and it actually lit up all the lights when
applied to these windings.

The secondary measure 0.4 ohms DC and 7.3 ohms with an ESR meter.

I was wondering if anyone can figure out if these measurements mean anything
or is there a better method to test this.



** What you have is a small SMPS that likely has never worked.

Full of SMD too - right ?

Worth about $10.

All repairers RELY on the fact that items used to work - therefore there is NO need to search for wrong parts, missing parts, parts incorrectly installed, missing or incorrect wiring or PCB connections between parts.

When an item has been tampered with or there are signs of attempted repairs, most techs refuse to touch the job - because of the same issues.

OTOH, you have to look for all of the above with an item that is damn near repair proof by design.


.... Phil

Phil Allison wrote:
David Farber wrote:

I was given a Hercules XPS 2.140 Slim speaker system. The owner
purchased it new from Amazon and it never worked. It sat around
longer than the return period so I inherited it. The problem is that
the 16 volt 1.4A power adapter is not working. I cracked open the
box and could not find any obvious faults. In circuit, the 68uF 400V
filter cap charges to the peak line voltage but that's about all
that is happening. I cannot measure any oscillation at the MOSFET. I
removed the MOSFET from the circuit and did the quick DMM check
where you put some voltage on the gate and drain and then check the
resistance between the drain and source. That test passed. The D-S
resistance went down to two ohms.

I removed the switching transformer and took these measurements:
Primary winding that goes to the MOSFET: 0.3 ohms DC.
Then I used my ESR meter on the primary windings and it measured 32
ohms. There is another primary winding (at least it's on the same
side of the transformer as the winding that goes to the MOSFET and I
think it feeds back to the controller) that measures:
0.4 ohms DC
The ESR meter measures open circuit.
I used my Bob Parker LOPT tester and it actually lit up all the
lights when applied to these windings.

The secondary measure 0.4 ohms DC and 7.3 ohms with an ESR meter.

I was wondering if anyone can figure out if these measurements mean
anything or is there a better method to test this.



** What you have is a small SMPS that likely has never worked.

Full of SMD too - right ?

Worth about $10.

All repairers RELY on the fact that items used to work - therefore
there is NO need to search for wrong parts, missing parts, parts
incorrectly installed, missing or incorrect wiring or PCB connections
between parts.

When an item has been tampered with or there are signs of attempted
repairs, most techs refuse to touch the job - because of the same
issues.

OTOH, you have to look for all of the above with an item that is damn
near repair proof by design.


... Phil

Hi Phil,

All very good points about repairing something that never worked. However I
did forget to say that there is a QC PASSED sticker on it so it *had* to be
working when it left the factory. :-p

Thanks for your reply.
--
David Farber
Los Osos, CA

On Monday, February 15, 2016 at 3:51:05 AM UTC-5, wrote:

To me, the more interesting part is the circuitry inside the speakers,
which manages to perform a miracle: 32 W "RMS" audio power output from a
22.4 W power supply.

It probably could do 32 W for a split second while the secondary caps discharge..

Den 15-02-2016 kl. 19:26 skrev David Farber:

However I
did forget to say that there is a QC PASSED sticker on it so it *had* to be
working when it left the factory. :-p

That sticker only indicates that someone at the factory have the task of
putting the stickers on.
It does not indicate that the unit has been tested :-(


--
Uffe

Uffe Bærentsen wrote:
Den 15-02-2016 kl. 19:26 skrev David Farber:

However I
did forget to say that there is a QC PASSED sticker on it so it
*had* to be working when it left the factory. :-p

That sticker only indicates that someone at the factory have the task
of putting the stickers on.
It does not indicate that the unit has been tested :-(

Hi Uffe :-)

My sticker comment was meant to be taken as sarcasm.

Thanks for your reply.
--
David Farber
Los Osos, CA