Sub-woofer not working. Plug fuse OK.

bluesnake

on http://tinypic.com/view.php?pic=20f3h1t&s=8

the blue yellow black and red wires are held with a black twist wrap. along the red wire there is a thick black bit that has red wire coming out of each end..... is this an in-line fuse? Is it working?

bluesnake

to test the windings of the trasformer for an open circuit.

make sure mains is not on, and use an ohm meter that there is continuity between red and red, blue an blue. one set of black and yellow should have continuity, the other yellow and black should have continuity, and the yellow to yellow should have continuity, Actualy the resistance of the first yellow measured to the black and the second yellow and black should be close in ohms, but will probably not be the same.

Crabman

Tested the in-line fuse within the red cable and it is working.

Unable to test red-red as only one of the red cables is accessible by the meter terminals.

There appears to be continuity:

Blue-blue: 1.3
Yellow - black: 2.0 / 1.7 (tested each of the two yellows against the single black, hence two readings)
Yellow - Yellow: 3.0

May as well try replacing the thermal fuse from Maplin (thanks for the idea and the link), or failing that the transformer. However it seems that the thermal cut-off is probably the culprit here.

bluesnake

Crabman wrote: »

Tested the in-line fuse within the red cable and it is working.

Unable to test red-red as only one of the red cables is accessible by the meter terminals.

Try harder!

With regard to http://oi62.tinypic.com/20f3h1t.jpg Use the probe on the right hand connection of the fuse holder (the red wire that comes out of the fuse to the transformer) as one connection point, I will call 'X'.

From this one point there are measurements to do with ohms setting and the unit not plugged in to the mains :-

measurement 1: the other red wire turns into a blue wire and runs to the plug connection underneath the panel where the mains goes in. connect the probe to that mains pin and point X. If you get a reading your transformer is fine.

measurement 2 :If there is no reading, then you may as well strip the heatshrink around the where red wire turns into a blue wire and measure from there to point X. if there is still no reading, then the transformer or thermal fuse is duff. this thermal fuse is normally inside the transformer and is not normally a replaceable part, but do look for it and prove me wrong . If you are replacing the transformer, make sure the replacement has the exact same voltages, but higher currents as it less likely to get as warm.

However I would expect measurement 1 to give a reading on ohms. if it does give a reading then my first suspect would be the power switch, the second suspect the power socket and third, the power cable and plug.

espresso

Crabman wrote: »

May as well try replacing the thermal fuse from Maplin (thanks for the idea and the link), or failing that the transformer. However it seems that the thermal cut-off is probably the culprit here.

Yes it is the most likely cause of the fault. Is is very unlikely that the transformer windings are damaged as they are effectively protected by the in-line fuse that you have tested and in-line thermal cut-out.

Unplug the transformer secondary output connectors from the circuit board and then unsolder the primary mains red wires. Undo the bolts holding the transformer to the panel and you should be able to dissemble the transformer and reveal the thermal fuse/cut-out sitting on the windings, perhaps glued in place with a few layers of tape holding it in place.

If you test for resistance at the mains plug (live/neutral) with the mains switch on, it is likely to be open circuit. The switch can easily be checked for continuity and you have already checked both fuses, leaving the thermal fuse as the number one suspect.

You couldn't get a much easier fault to repair now that you have almost located the faulty component - cheap part as well.