Need tech help with Phantom Power problem
So we are rocking out at a gig last night and our lead guitarist's mic goes dead - the only thing on the board that requires Phantom Power. We turn and twist knobs, jiggle the connections, and it comes back on for a brief time, then dies out again. We start channel hopping all over the board with similiar results. Meanwhile, all our regular XLR inputs are rock solid. Only the condensor mic is giving us a problem.
So, I am now trying to figure out where/what the problem is. My mixer is a 6 month old Behringer SX3242FX which, until last night, has not had any problems. I have a 100 foot 24X8 XLR snake running up to the stage. From there, the mic cable was about 15 feet to the mic. Everything is still under warrenty, but I hope to find the problem and fix it myself rather than having to send in equipment we need for our gigs - especially since I don't know where the failure is. My gut tells me that the problem is in the Phantom Power supply to the mixing board, because I just can't believe that all those other channels on the snake went bad. Having said that, I am wondering if Phantom Power is lost over the distance of a 100 foot snake. Or maybe it was just his microphone? We ended up plugging in a regular backup mic (Nady SP-1) for the rest of the night.
Anyway, I need some advice on how to troubleshoot my system before giving up and sending my equipment off to be checked. I am looking at getting a cable tester like the Behringer CT-100 http://www.amazon.com/gp/product/B000CCIVCA/ref=s9_simz_gw_s0_p267_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-2&pf_rd_r=00JGV6NJZCJNANJX8A5W&pf_rd_t=101&pf_rd_p=470938631&pf_rd_i=507846 because it has the ability to check Phantom Power problems as well as regular shorts in cables. Only thing is that I also have Speakon cables and the CT-100 does not have Speakon connectors. I could live without Speakon testing if I had to, but if I end up buying a cable tester it would be nice to get one that does it all. I don't know how much to trust the user reviews on these cable testers, it seems that one website has a unit marked high and the same unit on another website has it marked low. Anybody got some suggestions on whether or not a cable tester is a good tool or not? Up till now I have just been using a voltage tester and checking for continutity.
I will be calling Behringer about the mixer and the company that built the snake tomorrow when they open for their advice on troubleshooting. I'm just afraid that they may want me to send in everything under warrenty. I am more interested in learning how to troubleshoot my system so if something fails during a gig, I know what is going on myself. If I am confident that a unit has failed, I will send it in for warrenty repair, but at this point, I really don't even know how to troubleshoot and isolate my problems.
Any of you smart guys out there dealt with this problem? I would certainly appreciate some guidance here. Thanks in advance.
So, I am now trying to figure out where/what the problem is. My mixer is a 6 month old Behringer SX3242FX which, until last night, has not had any problems. I have a 100 foot 24X8 XLR snake running up to the stage. From there, the mic cable was about 15 feet to the mic. Everything is still under warrenty, but I hope to find the problem and fix it myself rather than having to send in equipment we need for our gigs - especially since I don't know where the failure is. My gut tells me that the problem is in the Phantom Power supply to the mixing board, because I just can't believe that all those other channels on the snake went bad. Having said that, I am wondering if Phantom Power is lost over the distance of a 100 foot snake. Or maybe it was just his microphone? We ended up plugging in a regular backup mic (Nady SP-1) for the rest of the night.
Anyway, I need some advice on how to troubleshoot my system before giving up and sending my equipment off to be checked. I am looking at getting a cable tester like the Behringer CT-100 http://www.amazon.com/gp/product/B000CCIVCA/ref=s9_simz_gw_s0_p267_i1?pf_rd_m=ATVPDKIKX0DER&pf_rd_s=center-2&pf_rd_r=00JGV6NJZCJNANJX8A5W&pf_rd_t=101&pf_rd_p=470938631&pf_rd_i=507846 because it has the ability to check Phantom Power problems as well as regular shorts in cables. Only thing is that I also have Speakon cables and the CT-100 does not have Speakon connectors. I could live without Speakon testing if I had to, but if I end up buying a cable tester it would be nice to get one that does it all. I don't know how much to trust the user reviews on these cable testers, it seems that one website has a unit marked high and the same unit on another website has it marked low. Anybody got some suggestions on whether or not a cable tester is a good tool or not? Up till now I have just been using a voltage tester and checking for continutity.
I will be calling Behringer about the mixer and the company that built the snake tomorrow when they open for their advice on troubleshooting. I'm just afraid that they may want me to send in everything under warrenty. I am more interested in learning how to troubleshoot my system so if something fails during a gig, I know what is going on myself. If I am confident that a unit has failed, I will send it in for warrenty repair, but at this point, I really don't even know how to troubleshoot and isolate my problems.
Any of you smart guys out there dealt with this problem? I would certainly appreciate some guidance here. Thanks in advance.
Comments
You can use a multimeter to check the dc voltage right at the mic female end. Pin 1 is Gnd and 2 and 3 will carry the 9-48vdc (depending on the gear). You can confirm operation right from the console, through the snake and to that user mic cable. Use the DMM and measure using the ground of the meter at pin 3, then test for 48Vdc on the outer pins 2, and 1. IOW, leave the gnd of the meter at pin 3, then with the pos lead of the meter, go to pin 1 and then 2. For a female end, looking into it with the gnd pin down (pin 3), pin 1 is to the R and pin 2 is to the L of center. At the other end of the male connector pins 1 and 2 are reversed. It doesn't really matter since 48v is applied to both pins 1 and 2 with a common gnd pin 3.
You can verify the same at the console with a multimeter. Turn off the PP switch. Set the meter ground at pin 3, turn ON the PP then measure both from 3 to 1 (R), and from 3 to 2 (L) at the input jack of the mixer channel. If you do not find the DC voltage there, try another channel and do the same. Then you can isolate whether the components feeding the jack are open or if the 48v PP source is inoperable.
Could be his mic. It's not uncommon to have the little resistors in the mic itself at the male XLR pins break off or be loose causing intermittents.
Another note is ALWAYS disable PP when connecting mic's. Usually you'll get an audible pop, but be careful because that transient can blow a mic pre on a lot of boards. I see that very very common with blown channels. Same with OH mics or pencil condenser mics with switches. Turn the switch on the mic ON then apply PP at the desk.
Those cable testers are extremely handy and a must for any gigging musicians. The nice thing about them is you can jiggle the wires connected to see which end has the stress points or opens. As you jiggle the wires once connected to the testing jacks, Leds will indicate continuity. If the LED's flicker while you move the wire or jack, you can determine it defective, but you can also determine which pin or signal line is the culprit. Cables don't usually short circuit, but they \"open\" more frequently. Confusing the terms is common, but and open circuit means the wire is broken or not connected.
Speakon cables are usually pretty hefty and so are the connectors. I wouldn't worry about a tester not having speakon or twist lock capability. Speakon connectors can have multiple connection schemes for the source path so it would be tough and add more confusion with a tester box. IOW if you have biampable cables and routings where some carry pins 1+ and 1- but also can carry 2+ and 2- at the same time (4 wire). A basic speaker wire (2 wires) with a speakon termination will usually be pins 1- and 1+.
Before you get ready to send the mixer in for service, check the PP with another known good condenser mic and cable. Check all channels. If the PP and mic are providing signal at the desk, then your problem is external ie the snake, termination points at the snake box, or the user's cable and mic.
Anyway, I appreciate the info and feel much better now. I did not want to send any of my equipment in to the repair shop, losing time and money, unless the equipment was actually damaged. At least now I know how to test it before sending it in. Thanks.
We had a gig on Friday night and about an hour into the gig, same problem. Phantom power mic going dead again. WTF??? Anyway, turned the gain up really high on his channel and got through the night. Went home after the gig, still thinking about that problem, and it occured to me that the only thing I had changed for the live gig is that we record the music on my multi-track recorder, using patch cables jacked into the I/O insert of the mixing board.
So, Saturday night gig soundcheck I tell my sound guy if the Phantom power mic starts going out again, to pull the patch cable from the mixer to the recorder. We get into a little discussion about the signal path of the patch cord and I explain to him that if the patch cord is shorting out, it would affect the signal pre-fader. He was not following me too well, but bottom line I told him to pull the patch cord if the Phantom powered mic started having problems again. Trust me.... Second set, the Phantom powered mic starts losing signal again, the sound guy pulls the patch cord, and everything was fixed.
I spent hours and hours troubleshooting my board and equipment only to discover that one of my patch cords was bad. It just so happened to be on the same channel as our one and only phantom powered mic. What are the odds? The patch cords are handmade and soldered by my sound guy because they have a special configuration of one end being TRS and the other end being TS. It is a special cord just for recording out of this board because the I/O plug on the board was designed for dual purpose. So, we are going to resolder that patch cord and hopefully next gig there will not be any problems.
As far as troubleshooting, I got smart and numbered my patch cords, 1-8, for the multi-track recorder so that I would know which cable was bad if the recording was mucked up on any channel. That helped because the second night I knew exactly which cord to pull if there was a problem. If I would not have numbered the cords, we would be wondering why the bass guitar signal was all hosed up and which patch cable we used, for example. Numbering the patch cords and plugging them into the corresponding inputs on the recorder narrowed down lots of variables.
Thanks for the advice on troubleshooting my board with the voltage meter and other suggestions. I really learned alot about my board through this experience. Once you understand the signal chain, you have a much better chance of finding, and correcting, the problem.
I had a fairly elaborate system I had worked on. They wanted the rack rewired and more organized, plus they had a few units with bad jacks on the inserts. I fix all those, get everything wired and dammmmit missing a channel! I start testing settings on the processors, checking everywhere. Going crazy for a good two hrs checking this big multipin that connects one rack to the next.. then it starts working. After an hr it starts to cut out again. Scratch my head and start checking things more.
Guess what I missed checking? I had ran through everything but the SPEAKER CABLES. One of them was bad!
What messed with me was their power amps have an internal protection that if the load is open, it MUTES the channel !
So I tore everything apart for nothing :evil:
OK, I blew it. My only excuse, and a poor one at that, is that we only had 8 patch cables. I had given my sound guy some more wire and tips to make extra patch cords so we could swap out patch cords, but he did not have the \"extras\" made up yet. I was so worried about my new 32 channel mixer having problems, that I immediately started troubleshooting the board. Then I started looking at the snake. I guess I was too concerned about the high $$$ value items that I forgot about the simple patch cables. And since I was doing the troubleshooting at home, I did not have my multi-track recorder patched into the board. After Friday night, I realized that the only thing I had not thought about was those stupid patch cords we use for live recording. That was the eureka moment for me.
Having said that, I still don't quite understand how the signal on the phanton power mic could be working fine for about an hour and then start losing strength. I can only imagine that during the night the cables get bumped and that was enough to cause the short in the bad patch cord. At any rate, removing the cable solved the problem.
I agree. That's why I try to make the time to close a thread I start, at least.
What's worse is when this happens at a gig. Been there done that dozens of times. I have constantly reminded band members when they wrap cables to do so a certain way instead of the elbow wrap and twist method they use. It's usually every other gig we find a defect cable somewhere.
Since you are using insert points with phantom power, it depends on the units but if one shield touches pin 2 you can have problems. Open connections are not going to load the signal path down as much as a short between cable points. There have been some boards made where the inserts load down the external source when using PP. As an additional lower than normal impedance path is created by lifting the insert point typically if someone uses a cable that is XLR to TRS insert or TS to TRS and PP is applied on all ch's. In that case, a short in the cord can really pose a problem. Some guys have inserted trs cables half way to remedy that problem, but I would never recommend that.
Your consoles may not have individual PP options. Some of the multitrack recorders do have individual or 2 ch ganged PP options. That actually helps provide some isolation for insert points from other consoles.
Anyway, glad you figured it out. Always have some spares!!
OK, now you've hit me twice in the same thread! I always do the elbow wrap and twist method for my stage cables. That is the way I was taught. If that is the wrong way, what is the correct method? Spank me one more time, thank you.
Though elbow to palm is speedy, I just loop over open palm.. no stress no accidently giving the end piece a quick tug no matter how innocent it may seem, no unneccessary twisting.
That's the way I do it... I got out of the habit of elbow to hand thing yrs ago... for reasons totally unrelated to the music scene! LoL
They don't tell you how at stores because they want you to keep breaking them. 60% of cable defects are cable management problems. Wrapping cables around your elbow stresses the wire and can cause tangles and other things. If properly wrapped, you should be able to toss a cable outward and it will unwind with no kinks, or tangles. It does take practice but THE BEST cable management wrapping technique is the over under loop.
You can do similar technique for electrical extension cords and save the misery of tangled 150' lines and looking like a dweeb in your front yard as you have half the cable still in tangled ball of mess dragging it around your yard while you have maybe 20' of cable free to work with!
I showed the guys in our new band the proper method. Normally they had gone through 10-15 cables every 6 mos, but using the right method, setup and teardown is fast, and cable replacements are not as frequent.
Rawb's method is clean, but I've still seen many tangled cords this way. Over under pretty much solves any kinking or tangling problem.