"Meat Plow" wrote in message
...
On Fri, 14 Nov 2008 22:44:46 +0000, Eeyore
wrote:

This is a well established technique for preventing voice coils burning
out under conditions of 'overdrive'.

There is a stage monitor I'm having problems with that uses this method.

The HF sounds very distorted and almost cuts in and out.

I looked closely inside and found some damaged push-on terminals. Ah, I
thought, probably a poor contact causing the probelm, replaced them,
checked driver DC resistances etc, reassembled thinking I'd probably
fixed it.

But no, the low level HF and distortion continued.

I'd checked the DC resistance of the protection bulb but later it
occurred to me that it might have 'very nearly' burnt out and have a
weak spot that wouldn't show up on a DVM but passing signal would heat
it and cause this trouble. I'll be able to find out soon enough but I
wondered if anyone else had ever encountered this ?

In the meantime I brought the HF driver home to check it's not voice
coil rub.

Graham

Been using some Wharfedale stage gear for a year or so. The mains are
all protected by lamps. I've replaced two in a year but not
experienced a distorted HF. You'll find problems in the xover or drive
I would assume rather than the lamp.

or maybe it's time to upgrade from that MI grade junk your using
George