Any idea why this PA on switch is tripping my fusebox?

[tom1970]

Hi everyone, Thanks so much for the help/advice. As an experiment I tried bypassing the switch by just applying a temporary short across the solder terminals and this seemed to sort the problem (although there was one instance where when I did a turn on only seconds after turning it off it did trip*). I think I'm going to have to find a way to replace the switch but I don't have the equipment for enlarging the annnoyingly small 9mm hole. To further complicate things I thought I would undo the fuse holder at the back to check whether that hole might be suitable for an OFF ONN switch and in doing so managed to break the fuse holder (!) which I have since discovered is also bloody difficult to replace. The holder thread was 14mm in diameter with a 15mm mounting hole. I need a beer!

* I'm guessing that the thermisters hadn't had a chance to cool off - assuming there are some.

 

[tom1970]

If it's the earth leakage section causing the trip you need a test for insulation resistance possibly on the transformer.
I doubt such a small transformer would create a current inrush problem on the actual circuit breaker section of the earth leakage.
I have had isolation transformers on medical isolation units do this but they are much, much larger.
A way to verify if you think that is what it might be would be to run a 10ohm 5 watt resistor in series with the primary just for a test.

I think the transformer is quite big. Prob is it is hidden under some kind of metal dome which is pretty fiddly to get out (see this pic http://blog-imgs-30.fc2.com/p/u/r/puredigital/FOSTEX.jpg). But the dome takes up quite a bit of space.

 

[Martaine2005]

The problem is the arcing switch.
And subsequent’on off’ before the NTC has returned to normal high resistance.
Prove it to yourself. Take the switch out and use the socket switch as the main switch.

Martin

 

[tom1970]

The problem is the arcing switch.
And subsequent’on off’ before the NTC has returned to normal high resistance.
Prove it to yourself. Take the switch out and use the socket switch as the main switch.

Martin

Yeah I think you're right. I tried bypassing the switch (see above) and it did seem to correct the problem. Thanks again.