Film-Tech Forum ARCHIVE: Stumped USL with JS-200 problem

This is topic Stumped USL with JS-200 problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Zachary C Washburn (Member # 3390) on 01-14-2011, 02:38 PM:

I am using an Ultra Stereo JS-200. About 3 weeks ago I have a problem with my format card where i have next to no sound in Digital or stereo channels. I could play in SR but the sound would drop out completely intermittently. I swap out the card with another JFM. Problem solved. Today we go to run the 1st show and about 20 minutes into the feature i lose sound in digital. I rush to the booth to see what the problem is. The DTS has dropped out and switched to the N/Sync channel. I go to manually switch to SR and find that it will not let me. Go to throw it in stereo and the same problem. Put myself into bypass turn the volume up and go to the porthole to check it. I have sound. Go back to the US and see that my -15v has just gone out on the power supply. Rush to get a new power supply and no more than 2 minutes later I have lost the +15v as well. Change out the power supply and voila! I have full sound in both Stereo and Digital channels, However I am completely unable to switch to SR channel. Try swapping out my old format card to see if the problem persists and suddenly what was a broken card now works fine in SR/Stereo/Digital formats. Any Ideas? My regular tech and USL are leaning towards the possibility that the DTS relay could be shorting out my format card.

Posted by Steve Guttag (Member # 268) on 01-14-2011, 03:23 PM:

First off...does your power supply have a "bypass" switch on it (I don't mean the one on the format module). If the answer is YES...then your problem at least STARTS there.

Remove the bypass switch and install jumper wires to simulate the bypass switch in the non-bypassed position. You'll be amazed at the number of problems that fixes.

While we are on the subject of USL bypass switches...the one on the Format module is a problem child too. I strongly recommend changing it out for a version with gold contacts...that has solved many a drop out issue.

To test if the DTS player is the issue...unplug its control cable...if the problem goes...then it is your problem...but first start with the power supply's switch, if it is still there.

-Steve

Posted by Randy Stankey (Member # 64) on 01-14-2011, 03:56 PM:

I vote with Steve. Bypass that bypass switch.

The way I understand it, that switch is under spec. Virtually all of them will eventually self-destruct because they can't handle the current they have to carry.

It was an unwritten policy, when I was a tech, to proactively remove and jumper those switches at any opportunity. Whenever it was done these sorts of problems became non-existent.

Posted by Zachary C Washburn (Member # 3390) on 01-14-2011, 05:15 PM:

When I switched to "Bypass" it was on the format card. I do have a bypass switch on the power supply that I swapped out for but I am not running the power in bypass. In the off chance that I ever do need to run in bypass on the power supply I have all of my auditoriums equipped with the recommended DC adapter.

I think the better question is. Why would the same problem exist in 2 format cards? Speculation would lead me to believe that a problem may exist somewhere on the backplane. Which USL says is the usually never the case, hence the design for their modular unit. And what are the odds that the DTS unit relay would pulse to the point of frying out a JFM and/or the power supply?

Posted by Gordon McLeod (Member # 33) on 01-15-2011, 11:43 AM:

Power supply 1placetolook
the bypass switch on the formatcard is second
finally is it a DTS 6 or 6D
if itisa 6 then they have dry relay contacts
if it is a 6d then it uses a optoisolator

Posted by Dave Macaulay (Member # 813) on 01-15-2011, 01:41 PM:

The power supply bypass switch problem is the switch itself. I get your point about wanting bypass, but these switches have lost way more shows that having a bypass power supply has saved.
Try exercising the switch at least, it you won't remove it and solder in jumpers to make it on "normal" all the time. Shut off the power (main and standby) and switch the switch 50 times or so. That should clean any dirt from the contacts.
Remove and reseat all the circuit cards a few times too. Using a contact cleaner spray in the card connectors is a pretty good idea too then doing a few out/in cycles.
The DTS may be forcing a nonsync command but that's a long shot, I don't see how it could stop SR from selecting while allowing EXT and NS.
Since you saw power supply dropouts I would look for PS problems... and for that unit removing and jumpering the bypass switch is advisable.

Posted by Randy Stankey (Member # 64) on 01-15-2011, 02:18 PM:

If the DTS is misbehaving, a test would be to disconnect the format change wires and run it SR/Stereo. The DTS won't be able to send false commands to the processor that way but you will have to manually switch sound formats.

If the processor stays in SR/Stereo and plays fine you have confirmed that it is the DTS player causing the trouble. If the problem remains then it is the Ultra-Stereo processor.

From that point, you can focus your efforts on the malfunctioning equipment and go from there.

(Don't forget to reconnect the format lines when you have come to a conclusion!)

Posted by Gordon McLeod (Member # 33) on 01-15-2011, 02:44 PM:

I beleive the bypass power switch is to switch to a full +/-15v supply that can connect to the back not the little wall wart that powers the bypass preamp

Posted by Randy Stankey (Member # 64) on 01-15-2011, 07:09 PM:

Yes, the backup supply would be a bipolar +15/-15 power supply. The small plug-in module is for the preamps.

I don't think the external supply is worth it. If the main supply blows up, it's probably because of that stupid switch. If it IS that switch, you probably won't be able to switch it to the external supply, anyway.

I say you are far better off to have a spare for the main supply. If you are a large multiplex, say one spare for every 10 units.

If the supply goes, you're going to have to go to that unit and switch in the backup supply and ensure it is working. But, if you have a spare for the main supply, you just slap it in place and you're good to go. It's about the same amount of work. Then you just send the old one out for repair.

You are far better off that way and you'll save a heck of a lot of money.