Genelec M040 woes and fixes.

[Hugh Robjohns]

I genuinely can't remember the last time I had to replace a blown fuse.

So to my way of thinking, if a fuse blows there's something seriously wrong somewhere, and just dropping in a new fuse without full and proper investigation of defective product is crossing a red-line.

I'm not a fan of soldered-in fuses, but better that than no fuse at all, and almost certainly safer for both the user and the equipment because an idiot can't chuck in any old fuse that comes to hand to try and get it working again!

[James Perrett]

The last time I replaced a blown fuse the replacement promptly blew too. That told me that there was something seriously wrong with the piece of kit which turned out to be a faulty mains transformer. I couldn't find a suitable replacement at a sensible price so the active speaker got turned into a passive speaker.

[ef37a]

The last time I replaced a blown fuse the replacement promptly blew too. That told me that there was something seriously wrong with the piece of kit which turned out to be a faulty mains transformer. I couldn't find a suitable replacement at a sensible price so the active speaker got turned into a passive speaker.

That was incredibly unlucky James. In some 50 years "in the trade" I don't think I have had more than two or three conventional transformers fail. That excludes TV Line output types, some of those were rather feeble!

One of the few was wrecked by the owner of the amp and one in an HT-60 sticks in the brain. The bias winding had gone short to frame one end...that took me on a merry dance to diagnose! That was on a pre-production sample, never happened again.

Dave.

[James Perrett]

That was incredibly unlucky James. In some 50 years "in the trade" I don't think I have had more than two or three conventional transformers fail. That excludes TV Line output types, some of those were rather feeble!

Yes, LOPTs were a regular replacement when I worked in the TV shop (not me doing the replacing though). The faulty mains transformer was an Indian made toroidal transformer which lit up the lamp limiter even with nothing else connected to it. These speakers led a fairly hard life in a rehearsal room before I bought them and had apparently been repaired a few times in the past.

[ChristianPerucchi]

Hey @Wonks i got the parts, im having a slight issue trying to access the board , cant take it out it gets held by the transformer did you had this issue too?
thanks!

[Wonks]

No, but it's probably got slightly different circuit boards being 50W+30W as against the 80W+50W of the M040. It's also a smaller enclosure so fitting everything in is more complicated.

When I look on the web for pictures of the M030 circuit boards I'm only finding my picture of the M040 board as anything vaguely similar.

The forum doesn't host pictures but if you can take some, host them elsewhere and then link to them, we might come up with some suggestions.

[ChristianPerucchi]

Thanks so much for your response! here are some pics!
so you can see for getting the board out i have to take the transformer but the nut and bolt turn together so i cant take it apart. on the other side you cant use much force because you make break the switches





[url]https://postimg.cc/Hc1Y3XK2



https://postimg.cc/p9MsqdWv



https://postimg.cc/gallery/sr6Gfr8

https://postimg.cc/p9MsqdWv

[Wonks]

I can't see the transformer bolt in much detail, but if the end doesn't already have two flat sides to it, you could get a file and file two straight sides on the very end of the bolt, just enough to get a spanner or a pair of grips on.

Hopefully enough of a grip to hold it in place and stop it turning whilst you put a spanner on the main fixing nut to loosen it. Once loose, it should then come off fairly easily.

[ajay_m]

Anything metal that turns and you can get a grip on can generally be persuaded to stay still using a pair of needle nose vice grips and some 800 grit sandpaper to stop you chewing out the metal.
Every toolbox should have a pair of these along with a pair of locking forceps and a right angle screwdriver with a set of bits for those impossible clearance scenarios.

[ChristianPerucchi]

Thanks so much for all your help Specially Wonks!
Working perfectly now, the nut was defective so after grinding the bolt end flat to grab it with a plier and take out the bolt i change it for a new one that works perfectly and doesnt jams, this speaker passed thru a previous repair maybe the same type of fuse change, it was full of old greasy flux, and blobs of old solder, solder over the fuse too, so i think it was not a very tidy job and maybe that is why it failed.
here are some pics from the repair
https://postimg.cc/gallery/t63SGjP

[Hugh Robjohns]

Congrats on the successful repair.

[Wonks]

Well done!

Yes. looks like it's been repaired before. I don't know why they didn't replace it with the fuse-holder version.

Glad we could help.

[ChristianPerucchi]

Oh when i cleaned the area the alcohol rubbed the fuse ink... look out for that if you are going to repair it too

[ChristianPerucchi]

Notice the rubber gasket a little worn too, so we have to be careful with that, i wonder if there is any replacement for it, also how much time this repair will take before ir blows the fuse again, i wonder if we have to leave it powered on all the time and mute the soundcard instead of using the powerswitch

[Wonks]

I leave mine on all the time and let the signal auto-sensing turn the speaker on and off.

[ChristianPerucchi]

Nice! thanks wonks! hope the fix lasts hahah