Dolby 650 Microphone problem

[Martin McCaffery]

Dolby 650, Shure Mixer, 2 Shure wireless mics

User 2: Format 65
NS: Format 64

Our microphone PA system has quit working. It has worked fine for years and I haven't changed the set up. Generally run through User 2, but have tested on NS also.

The mic receivers' LEDs show signal being received when I tap on the mics, but no sound from monitor or speakers. I tried plugging a receiver directly into the 650 Mic in port, and still did not get any sound, so the problem is unlikely the mixer. And seems unlikely both mic receivers would stop outputting at the same time (they are on different channels, also).

I have reseated all of the cables.

A few weeks ago, I had to reset the boards in the 650. Is it possible I could have disturbed something mic related (this is the first time using the mics since before I reseated the boards)? Currently, no other sound problems.

Ideas?

[Carsten Kurz]

Mixer?What Mixer? Does it have a headphone output? First check wether the audio is actually output from the mixer. VUs are nice indicators, but, technically, not sufficient to make Shure that signal is actually leaving the device.

[Jim Cassedy]

As Carsten says, I'd double check the mixer output, either using headphones if it has a monitor jack or by plugging it into another amplifier of some sort.

Format 64 & 65 both enable the XLR microphone input on the back of the 650. That input expects to see a mic level signal, but since you say this has worked in the past, I assume your mixer was putting out a proper level to it. That being said, try bypassing the mixer and plugging a microphone directly into the XLR input on the back of the '650. ( You will need to either turn on or off phantom power with DIP Switch #3 on the front panel depending on which type of microphone you use) I had the mic input go 'dead' on a unit once many years ago after a big power glitch and 'de-programming" and "re-programming" the format 64 (or 65 depending on which one you use) buttons solved the problem and it has worked fine ever since.

(FYI: DIP Switch #3 UP= Phantom Power ON / DOWN= Phantom Power OFF)

[Marcel Birgelen]

Martin is also mentioning a receiver. So, this is a wireless microphone?

As such, the setup is as follows?

Wireless Mic ===> Mic Receiver ===> Mixer ===> CP650 ( ===> B-Chain )

[Martin McCaffery]

Yes, wireless mic set up as above ^
As mentioned in the original post, I tried plugging the wireless mic receiver into the 650 with no results. I did not try it with the Phantom Power. I will give that a try in the morning. I'll recheck the programming on the U2 and NS buttons.

[Marcel Birgelen]

The phantom power shouldn't be a thing for wireless microphones. The phantom power supplies the power many condenser microphones need to operate in-line (as in, via the same wires the sound is captured). On a wireless mic, there are no wires between the mic and the receiver/microphone pre-amp, so the power is always supplied by a battery.

Like Carsten indicated, if there is a headphone jack or a line out where you can plug in some headphones on your mixer, this is a good way to test if the microphone and wireless receiver itself is actually working. If you receive positive results that way, the source of the problem should be your CP650 and if you recently did a reset to factory default, there may be something wrong in the configuration.

Before working on a problem, it's often best to try to isolate the cause as narrowly as possible, by eliminating the good parts.

[Randy Stankey]

Is there an output gain or impedance setting on the wireless mic that has been accidentally changed?

There might be a "MIC/Line" setting or a "Lo-Z/Hi-Z" setting. The impedance setting might also be labeled "BAL/UNBAL." (For "balanced" or "unbalanced.") If either one of those have been flipped to the wrong setting it could cause a problem like this.

Like Marcel says, phantom power should be OFF. You do not need it. Dynamic microphones don't need phantom power and will ignore it when turned on but some equipment like your wireless microphone could malfunction or even be damaged if phantom power is turned on. The only time you need it is when you are using a condenser mic. In that case, a condenser mic just, plain won't work until phantom is ON. As a general rule, always leave phantom power OFF at all times unless needed.

Also, check your microphone cables. They might appear to be good on the surface but still not work. Check the solder joints at both ends of the cable. Be sure that the connections are sound and that there are no "cat whiskers" that might short something out. Check by feel, the entire length of the cable, to see whether it has any kinks or breaks in the internal conductors. (Kinked conductors and broken connectors are common when cables are tossed around, wrapped improperly or stored in a jumble.) Connect an ohm meter to the ends of the cable then shake the wire (not the connector) vigorously. If the reading jumps around when the cable is shaken, you have a bad conductor inside the cable. If so replace the entire cable.

XLR microphone cables are robust and work well if properly cared for but, in a stage or studio environment, they often get pretty beat up. When I worked at Mercyhurst, one of our big jobs in the summer (off-season) was to check and repair ALL microphone cables. Every mic cable was checked, tested with an ohm meter then stretched out on the floor to restore the lay of the wires before being remarked with color codes for length. Then they were properly re-wrapped and hung up, ready for another season. We had dozens of mic cables and, by the end of the year, at least half of them needed some kind of repair each summer. It got so bad, one year, that we decided to just toss out the bad ones. We bought a spool of cable and a ship load of connectors. That summer, we spent, probably, two weeks having "cable making parties" almost every day.

[Martin McCaffery]

Thankfully our cables don't get much abuse, they are plugged in and stay that way. As I said, I have reseated them, but I'll give them a check when I am up there.
As we have two microphones and two receivers, I doubt they both could have gone bad independently, but will check all of those settings again.
Have not done a factory reset. As per Jim's suggestion will check the U2 and NS. Buttons. Trying to find something I can use for headphones that will work with the mixer to test that.
Thanks for the ideas and I will report back.

[Martin McCaffery]

Update: Checking the buttons on the 650 and discover it won't allow me to change the button assignments. If I press the menu button the menu moves to the next menu level (room calibration). Turning the volume knob while in the button assignment only changes the Volume setting.
With #6 dip switch up, all the buttons say The Format (Install) ie: User Format 01 (install). I don't think I've ever seen the (install) before. Hitting the OK button does nothing. Putting #6 back down reverts the menu to the appropriate button and removes the (install).

All cables tested ok, btw.

[Randy Stankey]

Good to know that your cables have tested out OK.

The reason I went into all that detail is because, on the stage where I used to work, mic cables used to get run over by carts and stage wagons or pinched in doorways and things. The cables might LOOK all right but, inside, the conductors and insulation are crushed. There were people who would toss cables in a pile, step on them and run them over with things then act surprised when they don't work.

I didn't think your cables had been abused like that but, given my experience with idiots like that, I thought it was wise to mention.

[Marcel Birgelen]

Update: Checking the buttons on the 650 and discover it won't allow me to change the button assignments. If I press the menu button the menu moves to the next menu level (room calibration). Turning the volume knob while in the button assignment only changes the Volume setting.
With #6 dip switch up, all the buttons say The Format (Install) ie: User Format 01 (install). I don't think I've ever seen the (install) before. Hitting the OK button does nothing. Putting #6 back down reverts the menu to the appropriate button and removes the (install).

All cables tested ok, btw.

Well, the "(Install)" appears during the initial configuration, so it looks to me as if your CP650 has gone through a factory reset. This may explain the issues you're having.

In your first post you're mentioning "resetting the boards", what do you mean with that exactly? As in, what did you do to "reset the boards" and why was it necessary?

[Martin McCaffery]

Marcel: that was supposed to be "reseating" the boards. I popped the circuit boards out and back in again. We had some horrendous crackling in the left channel. I recalled that solved the problem once before, and it did this time. Didn't have any problems other times I took out the boards and reseated them. And blew the dust out while I was there.

Everything else with the sound appears to be fine. The film sounds as it should.

[Marcel Birgelen]

What you describe to me, the (Install) in the display and the Room Calibration, is exactly the initial configuration procedure of any "new" CP650... The "Calibrate SPL" step is usually the first initial configuration step. So I suspect that this reseating of the boards may have either wiped or corrupted the memory of the CP650, so it now thinks it's unconfigured, once you switch dip-switch #6 into configuration mode...

Have you ever saved the configuration parameters of your current configuration, for example via the Windows client software for the CP650? If not, I'm afraid you need to redo the initial setup, including the room calibration to fix this.

[Sam Chavez]

I get calls for flash memory now and again. Maybe this is why. I've never heard of a 650 that needed card reseating but there's always a first time.

[Martin McCaffery]

Marcel: Yes, I have backups, thankfully.
Sam: Is there a way to check the flash memory?