impecunious Posted July 20, 2014 Share Posted July 20, 2014 I have a number of these receivers and now four show an identical fault. The RF and AF displays show exactly as they should (Full RF and AF being modulated with strength of sound) but diddly squat output on either XLR or Jack, even with AF gain at +18. I have done the obvious, eg. reset, change frequency, Over modulate the AF ( suggestion on another thread) but all to no avail. I dabble with electronics ( the worst kinda person) and resorted to opening up a couple of the receivers and I managed to trace the signal as far as the two op amps (4850, output fine on pin 7) and then onto the 4851( used as switch for a series of potential dividers to attenuate the signal) and the output from the 4851 is also fine. What does it go through from there before it appears at the output sockets ? Can't be much, but I'm damned if I can find the path.Strange that 4 of 20 receivers have this identical fault.As an aside, could it be that at one time someone put the XLR output into a desk that had phantom volts and put 48V up their bottoms? If so is there any protection for the output stages of these receivers, or can I expect their output stage to be shot?Being intrinsically mean I don't want to throw these away and would prefer to repair. Senn, I believe will not handle G2 any more.I'm surprised that I haven't seen this fault on other message boards. Perhaps it's something in the Midland's air.ThanksD Link to comment Share on other sites More sharing options...
IRW Posted July 20, 2014 Share Posted July 20, 2014 ...G2......Perhaps it's something in the Midland's air... You never know...! :D Link to comment Share on other sites More sharing options...
nb705 Posted July 21, 2014 Share Posted July 21, 2014 Have you checked to see if the pilot tone is on? It's a simple mistake to make and it catches everyone out! Link to comment Share on other sites More sharing options...
Ynot Posted July 21, 2014 Share Posted July 21, 2014 Erm, G2... You are aware that unless your sets have been retuned, they're probably using the frequencies sold off in the last couple of years..??So even if you did get them working again they're most likely to be illegal to use now in the UK.. Link to comment Share on other sites More sharing options...
sam.spoons Posted July 21, 2014 Share Posted July 21, 2014 Erm, G2... You are aware that unless your sets have been retuned, they're probably using the frequencies sold off in the last couple of years..??So even if you did get them working again they're most likely to be illegal to use now in the UK..A UK spec, Range E, EW100G2 covers 830MHz to 866MHz so while the lower range is no longer usable it does cover the legal (and licence free) 663-665MHz section of C70. I only have one wireless mic and a guitar bug (also on C70) so on the rare occasions I use them I can do so legally. I think the OP would usually get maybe 4 of his G2s working together in C70 but probably not many more. Range B, C, and D units can be used on the licensed C41-60 and Range A likewise on C27-30. Careful setting required in all cases as all except Range B units all have overlap into the prohibited Channels. http://www.tlu.ee/UserFiles/Balti%20Filmi-%20ja%20Meediakool/Logod/SENNHEISER-EW100G2-Wireless-Microphone-USER-MANUAL.pdf http://www.shure.co.uk/support_download/frequencies Link to comment Share on other sites More sharing options...
Ynot Posted July 21, 2014 Share Posted July 21, 2014 Indeed - I was looking at the fact the OP has 20 of these, so pretty much discounted the option that he's trying to use them in the licence free band :) Link to comment Share on other sites More sharing options...
sam.spoons Posted July 21, 2014 Share Posted July 21, 2014 Indeed - I was looking at the fact the OP has 20 of these, so pretty much discounted the option that he's trying to use them in the licence free band :) Yup http://www.blue-room.org.uk/public/style_emoticons/default/biggrin.gif Link to comment Share on other sites More sharing options...
Solstace Posted July 21, 2014 Share Posted July 21, 2014 Frequency issues aside, Our 300 G2's showed this fault - turned out that a design flaw meant that despite being *designed* to cope with phantom power, some batches certainly didn't cope, especially if they were used with cheaper rackmount mixers. Some of ours (three of the original four purchased around Feb 2006?) died under manufacturers warranty, others didn't. Sennhesier's fixed repair/swap price policy came in handy on the latter, though this was a while ago and as others have rightly pointed out, the wireless landscape has changed since then!. You'll need to do your research to find out whether it's even worth repairing your faulty kit! Link to comment Share on other sites More sharing options...
IRW Posted July 21, 2014 Share Posted July 21, 2014 Indeed - I was looking at the fact the OP has 20 of these, so pretty much discounted the option that he's trying to use them in the licence free band :) Just to clarify, that's pretty much what I was getting at with my earlier tongue in cheek comment! As nb705 said, check the pilot tone. The manual, which I'm sure you will have looked at, implies that you can also adjust the audio output level, but if you've performed a factory reset, this should be something sensible. (Note, factory reset does not touch the pilot tone setting) Ian Link to comment Share on other sites More sharing options...
Sound Man Posted July 21, 2014 Share Posted July 21, 2014 There are a pair of green coloured surface mount resistors (one on each leg of the output) marked 100 that have probably gone open circuit or high in value. The only way that I can see that these would fail is if the output has been connected to an input with phantom powering. Link to comment Share on other sites More sharing options...
impecunious Posted July 23, 2014 Author Share Posted July 23, 2014 Hello again, Firstly thanks to anyone who has replied, esp to Sam s, ( yes I can squeeze about 5 into Ch70) and also Sound man. All components are tiny and surface mounted, but will track down those 100ohm resistors and see what I get across them. Thanks for that. Have found a clean signal on the board and may just try decoupling it to the output jack with a 0.1uf capacitor. Unbalanced is better than nowt. Thanks also for suggestions about pilot tone, but it was one of the first things I’d looked at. Do I conclude that some cheap desks don’t have a suitable current limit on their phantom supply? Just out of interest, if anyone doesn’t fancy paying senn prices for aerials, antennae amps and ASA1 splitters, then 2 Tv aerials ( of appropriate band for frequency) and 2 RF amps and a pair of 1 into 4 aerial splitters has worked really nicely for me. Also, 12V 3A switched mode PS with a 1 into 4 power lead splitter can power the receivers. Total cost around £100. I’d hate to calculate the senn costs. Can’t guarantee it’ll be good for you, but it worked for me. Maybe I’m lucky in that the steel girders in our space make it a fantastic faraday cage and so back front rejection or aerial directivity doesn't become critical. Nothing gets in or out. It’s hardly worth telling the audience to turn their phones off. thanks again. Am off to hunt a pair of miniscule resistors. Oh yes, thanks also Solsrtace for confirming that my fault is not unique. Well,Just had another look, there are two 100 Ohm resistors, (mine are black) one on the hot line, one on the cold. One measured about 3.0Meg, the other was open circuit. Thatn would correspond to no signal on one leg and the very very attenuated one on the other. Thanks everyone, it was worth perservering. Now, all I've got to do is unsolder. I have never removed surface mount before, and each resistor is slightly smaller than an ant's testicle. That's gonna be fun! I will youtube surface mount removal. If I can't be bothered to refit a resistor, will just get a 5B pencil and draw a thivck line between the solder pads. Anyone knoiw the resistivity of graphite ? Just kiddingThanksImp Link to comment Share on other sites More sharing options...
Robin D Posted July 24, 2014 Share Posted July 24, 2014 If the existing resistors are as good as open circuit, and there is a little bare wire on the tails, just piggy back the new one on the old. Much easier than desoldering surface mount! With care you may be able to break open the existing to give a longer tail to attach too! Link to comment Share on other sites More sharing options...
Sound Man Posted July 24, 2014 Share Posted July 24, 2014 The resistors are 10 ohm in value. 100 indicates 10 + no zero's to follow = 10 ohm. www.abelectronics.co.uk/tools/surface-mount-resistor-code-calculator Link to comment Share on other sites More sharing options...
impecunious Posted July 25, 2014 Author Share Posted July 25, 2014 Yep, they are indeed 10 ohm. In all the receivers that had gone, either one or both of these had gone O/C and where it was just the one resistor that had failed, it was on the supply for the hot pin. One of the receivers had been modded by senn as there were 2 x 10uF caps in series with these resistors. They still didn't stop one of the resistors failing though. ( Am surprised at that) Anyway, thanks for all your help, I was going to give up with these but you helped me persevere. I've included some pics to help anyone else who need to do the same. In the end I piggy backed my resistors, with flying leads, getting the surface mounts out was a hassle. Thanks again D PS can't seem to include pictures, might try again when I copy and paste to add pictures, they appear in my window, but when I try to post I get the message "! You must enter a post" What am I doing wrong? Link to comment Share on other sites More sharing options...
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