Tweet
I'm running two USL JSD-60 audio processors here at the drive-in. I've got one (on Screen 1) that experiences "random" audio drop-outs, where there is complete silence for about 4 seconds, then it returns to normal. When it goes silent, I've noticed the red "Bypass Mode" light on the right side of the unit turns on, and then as soon as the sound returns the light goes out. It only happens (usually) once a night, but its beginning to be an every night thing. These units were installed new in March of 2013. Anyone have a clue what would cause this?
-
-
Do you have it configured with the bypass power supply installed. One would hope that if bypass mode was triggering you would get the mono summed bypass audio, rather than no audio?
Other than maybe an automation command, i would think the only way to enter bypass mode is if the mains fail or the unit is turned off. So supply issue? -
Also maybe try having the monitoring software connected and see what that shows, if anything, during an interruption?Comment
-
Yes, the secondary power supply is connected and working. When the sound drops, it's just completely silent for about 4 seconds. It happened about 3-4 times during Joker tonight, but Beetlejuice Beetlejuice played all the way through as the second feature without any drop outs.
I left the system powered up tonight and plan on calling my techs at American Cinema Equipment to log in and see if they can pull the logs from the processor.Comment
-
I dont believe the JSD60 has log files to extract. I suspect you may need to reflash the firmware in the unitComment
-
Barry,
Try running on just the external supply and see what happens. Also look for a post by Harold H. and message him about this. He designed that unit and may be able to shed mors light about this. I put in quite a few, and far as I know, there are no logs recorded in it...Comment
-
I'm sorry to hear about the issue! The JSD-60 goes into bypass on absence of power and during bootup. It then goes out of bypass after initialization. It sounds like the system is resetting. There is a watchdog timer that resets the system on a software crash. On power up, the system logs the cause of the reset (power on, watchdog timer reset, etc.), so it would be interesting to see what the log says.
Years ago, there was an interesting problem with a JSD (I don't remember if it was a JSD-60 or a JSD-100). That theater had JSDs mute and then reset on loud audio in auditoriums at one end of the theater. It turns out there was a cellular tower just outside that end of the theater. The RF from the tower was being conducted into the JSD through the HI/VI audio output. I added series resistors at the JSD to drop the RF level leaking into the unit, and that fixed it. We later modified the design to eliminate this problem.
A look at the log would be interesting. It might be interesting to do a firmware update (see http://ftp.uslinc.com/Products/JSD-6...urrentRelease/ ). MAYBE the flash memory running the microcontrollers and DSP is becoming marginal.
Good luck!
Harold
Comment
-
Harold,Originally posted by Harold Hallikainen View Post
We recently (4 weeks ago) upgraded our FM broadcast antennas here at the drive-in. These new antennas really bumped the gain on the broadcast RF signal. The antennas are mounted on the gable ends of the building, but the antenna for the screen we're having the issue on is probably 8-10 feet away form the sound rack where the JSD-60 is located.
Could this be an issue that would cause this?Comment
-
As I think about it more, I think that problem was on the JSD-100. We had a path from the HI/VI outputs analog inputs on the microcontrollers so we could measure and display the HI/VI outputs levels. RF came down these lines and when there was loud audio, the peaks caused the substrate diodes in the microcontrollers to conduct, eventually causing the chip to crash. We fixed it by removing this circuitry and measuring the output level at the DSP instead.
It IS possible that this could be a problem in the JSD-60. I only heard of this being the case in one JSD-100 that I went out to investigate. I doubt the RF from your transmitter is enough to cause an issue, but you never know. Is there a piece of content that reliably makes it fail? If so, can you run that content with the transmitter off and see if it fails? Also, it would be nice to look at the JSD-60 log and see what it is reporting.
Good luck!
Harold
Comment
-
Before tonight's shows I lowered the output power of the Broadcast Warehouse BW TX-5 FM transmitter from 0.76 watts to 0.30 watts.. basically cut the output power in half. Didn't have a single audio drop out tonight. Don't know if that was the culprit, but we haven't had a single issue tonight. I'll get the USL software on my laptop and see about getting those logs.Comment
-
Interesting! I was not aware of any RF sensitivity of the JSD-60, just the JSD-100. If you can repeatedly show this is the issue (no problem with transmitter off, problem with transmitter on), you can try keeping the transmitter power down or install ferrite beads on all the cables (except AC power, which already has extensive RF filtering). Something like these ( https://www.dxengineering.com/parts/dxe-csb31-525-5 ) should help. On thin cables, you could loop them through twice.
Good luck!
HaroldComment
-
Be careful on the power level. Pretty sure even .3 watts doesn't comply with FCC Part 15 regulations for unlicensed low power FM. Just sayin... Not that any Drive in actually follows Part 15 Regs, or actually knows what it is.Comment
-
If the problem does turn out to be RF, I'd just move the offending antenna farther away from the audio rack... after installing the ferrites that Harold mentioned.
On power... I generally advise against advertising RF levels. A "better" antenna can infer some gain factor, effectively raising the wattage level above what's coming out of the transmitter.
As Mark says, compliance with Part 15 is not well understood, but in practice, operating within the rule means you can't get much beyond 150 feet, and external antennas are out of the question. The Ramsey transmitter, with the fixed telescoping antenna, is about as close as you can get to literal compliance. Legal adherence is a combination of transmitter power, measured strength of the signal at a certain distance and the type and location of the transmitting antenna. On a good day, a "legal" signal might get to the other side of your snack bar.
Today, I think the number of literal violators would be difficult, if not impossible to get under control. Most would be unaware, but include most wireless microphones, baby monitors, some institutional campus radios, external satellite receivers that transmit an FM signal to your car radio, drive-in churches and, IMO, most all drive-in theatres. It doesn't help any that ALL FM transmitters you see on EBAY, aimed at drive-in operators are outside the rules. I saw one yesterday that advertised a 2,000 watt transmitter, for use at drive-in churches and theatres, among other places.
That said, I've come to believe it's more the way we practice the art, than a literal application of the rule. A drive-in on top of a hill, putting a few milliwatts into a coat hanger can push a signal out nearly a mile beyond its boundaries, where a similar drive-in, in the bottom of a bowl, might run some 10 watts or so to get the same coverage. I've seen both.
If you're running your system during business hours, and extending your signal only beyond what is needed to adequately cover your property, and you're on a frequency that doesn't interfere with any local or regional station... commercial or non-profit, the chances seem historically low that you'll ever be bothered. On the other hand, if you're shoving a few hundred watts toward your local community in the middle of the day, broadcasting music and "public service announcements" about your show schedule, I think you're just daring the authorities to come knocking. In a bit under 60 years in/around the radio and drive-in businesses, I've seen that, too, but only once. More than one poster publicly questioned the mental state of the guy who was doing that.. Current rules allow upwards of $2 million for extreme examples of that kind of violation.
FCC field offices have been decimated by budget cuts. In my region, the closest office covers 3 states with only 2 inspectors. They are friendly, professional, and focused more on elimination of interference to legal signals than picking on "Mr. Microphone". That said, however, I think it unwise to go way outside the rules and stick it in their faces. The results of that can be unpredictable, and never in favor of the violator.Last edited by Jack Ondracek; 10-07-2024, 10:45 AM.Comment
-
I like moving the transmitter, ferrites, and tuning transmit power.
Additionally how is the unit housed in a rack? Covers off? Anything to shield it a bit better. And I'd test your intentional bypass mode and make sure it's doing mono audio as expected. Whatever it is causing it to reset seems to do so without bypass audio on the outputs. But that might be a product of whatever is resetting, not quite comparable to normal bypass operation.Comment
-
Barry,
You could try swapping JSD-60 units between screens, and see if the problem follows the JDS-60 to the other screen, or reoccurs in the same rack with the newly positioned JSD-60. The FM signal strength wattage sounds like overkill, especially if you are running it into a gain antenna.
Not sure if QSC is still offering a rebuild option on existing USL processors, but if the problem persists then that might be something to consider over the off-season.
Also, I am pretty sure I know someone with JSD-60s for sale if you are looking to acquire a spare.
If you can generate a log, definitely have Harold take a peak for you if he's willing.Comment
Comment