AKG WMS 40

[berry120]

To cut a long story short, I've got a fairly old looking AKG WMS 40 handheld wireless mic / receiver in front of me - and it's not working. Exactly how it got to it's broken state I'm not entirely sure - no-one seems to know! Both the mic and the receiver seem to power on fine, and the RF light lights on the receiver whenever the mic is switched on - so it must be transmitting something. But the audio output is completely dead, not even a hiss or a very faint signal as far as I can tell - and that's the same for the unbalanced jack and the balanced XLR outputs.

I've opened the receiver up and had a quick look around to see if there was anything obvious that jumped out as being wrong (i.e. no loose wires or dry solder joints I could see) but beyond that I haven't really got much of an idea what to test in it / look for.

 

Of course, I could just be trying to fix something that's not fixable at all, but I thought it was worth a shot. Has anyone got any ideas as to what I could try?

 

Thanks,

 

Michael

[KevinE]

Are you sure it's the receiver thats at fault? The RF light comes on when the receiver is locked to the carrier on the handheld, that's all. It doesnt mean the mic itself is transmitting audio. Check the capsule first in case it has drop-damage.

[timtheenchanteruk]

theres not a mute feature is there? I have had the switch go on a body pack that had a off, on but mute, full on switch. it would go to standby but not to full on. so in this case the receiver would pick up the carrier and everything would appear to be fine.

[berry120]

There is a mute switch on the mic itself, but it seems to be operating correctly - it's clicking reassuringly into place on both mute and on, so I don't think it's that.

 

Checking the capsule was the first thing I did, it seems to be absolutely fine, and the grill hasn't got any dents or anything in it that would point to the fact it was dropped.

[themadhippy]

Can you get hold of another reciver to check the transmitter,a scanner can be helpfull if you dont know the frequncy.

[drsound]

Do you have a signal generator or scope to hand? I know it's not kit that everyone has just lying around but if you know someone who might be able to help you out it's probably the best way forward. It's relatively easy with the sig gen to inject a signal into various points in the circuitry and watch the results on the scope. You can also put the scope onto the output of the capsule to check it. This should help you isolate where the fault lies. Then you've just got to work out which of the millions of surface mount components is faulty B-)

 

 

Otherwise I'd go with getitng hold of a spare and start with checking the transmitter and receiver against the spare set.

[berry120]

Ressurecting a bit of an old thread here now, but I recently got a chance to open this up again and have a look at it more thoroughly - firstly I went through and just cleaned everything up a bit, insides of the receiver were really dusty (not quite sure how that much dust managed to get inside in the first place!) But I basically just blew it all away, closed the thing back up again and then tried again. This time, I noticed that when I ramped the gain / volume up to full and waved the mic around, there was definitely something coming through... though by something I meant an occasional thud when I whacked the mic against my hand. After removing the windshield and then poking a bit more, there was definitely a noticeable crackle when I waggled the wires coming from the capsule.

This gave me an idea, I played some music, took an output into a DI box, and then to a mic cable with bare ends. I touched them against the outputs of the capsule, not really expecting that much, and woop, music comes through!

 

So is my thinking correct in that the fault of the mic is pretty much definitely with the capsule - and if so, what would be the best way to get another one? Is there a place I haven't found that stocks old spares, or would it just be a case of contacting AKG? I assume the mic isn't one in current production (it looks completely different to the WMS 40 pro on the website at the moment) so I'm partly wondering whether I'll be able to get my hands on one at all.