Film-Tech Forum ARCHIVE: Smart MOD II B -- Intermittent loss of sound.

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Posted by Randy Stankey (Member # 64) on 09-27-2005, 11:55 PM:

Problem occurred last night.

Upon starting movie: No sound.
Preamp card "Proj. #1" LED lit as usual.
Meters fluctuating normally.
No sound output in any mode. (Mono. Stereo. Dolby. Music.)
Slight static "crackling" sound heard in speakers & booth monitor.
I am unsure but I think I could hear faint sound coming from surround channel.

At first, I assumed it was a bad amplifier.
Installed backup amp. (Known to be good.) Negative results.

Rechecked speakers, wiring and other sound equipment. No results.

Finally, removed each card from processor in turn.
Visually inspected each.
Reinserted & ensured secure seating in connectors.
Rechecked external wiring betwen projector, processor and amps. All OK.

Suddenly, the thing decided to start working again.
I am not sure why.

Working hypothesis: Loose connection in edge-card holder. Likely culprit: Output Card or Format Card.

At this time, system seems to be working normally but I am not fully confident. I fear that this is a precursor to final failure.

Should I be ordering replacement parts in anticipation of the showdown?

Honestly, I would prefer to have a nice Dolby processor. (CP-65)
Not only would I be more confident about its long term reliability but it would provide a better upgrade path for future digital sound. Furthermore, it would give better sound.
Smart MOD II B are OK "starter" units for the budget conscious bean counters but virtually nothing beats a realy Dolby.

My assessment of the situation is that our processor is going to require service fairly soon. The money spent in repairing it would be better spent in buying a better system.

What do you all think?

Posted by Dustin Mitchell (Member # 372) on 09-28-2005, 02:44 AM:

For the longest time we had an intermittent sound problem in a Mod IIC. Upon initial powerup the stereo A and film SR formats would not work, however, the digital and mono would be fine. Furning off that sound rack and turning it back on would fix the problem. It got to the point that whenever I opened I'd flip on all the breakers, wait 5 seconds, flip the breakers for that rack off, wait 5 more seconds, and flip them back on. We tried everything, format card, matrix card, pre-amp, even an entirely new chasis. Nothing.

Then one day I had a power supply fail in another sound rack. I took the one out of the problem rack and used it to get the other one up and running. When the new power supply came in the next day I put it in the 'defective' rack. What would you know but the damn problem moved. It was the power supply all along.

Since then there have been one or two other wierd problems with these mod IIc's that have been solved by merely changed out the power supply.

Not sure if it will apply to your situation or not but I'd think it would be worth checking out, especially if Smart will do a repair/exchange for you.

Posted by Gordon McLeod (Member # 33) on 09-28-2005, 02:07 PM:

The card edge stip connectors often become intermitent (this is true of all connectors)

I usually clean them with some contact cleaner and insert them several times

Also if you a dsp matrix it can some times locks up and needs to be reset

Posted by Mark Gulbrandsen (Member # 72) on 09-28-2005, 05:44 PM:

quote: Gordon McLeod
usually clean them with some contact cleaner and insert them several times

Normally the gold plated edge connectors don't caue problems unless cards have been cnostantly plugged in and out causing some wear to the contacts. Of you do clean the contacts use Pro Gold by Caig Industries. NASA uses it on shuttle connectors!
The Best Contact Cleaner There Is!

Mark

Posted by Randy Stankey (Member # 64) on 09-28-2005, 07:38 PM:

Yes, the Media Matrix DSP locks up fairly frequently.
It's a PITA some times. There is a switch that quicky resets it.
This is one of the things I checked.

I rarely have to touch the Smart processor. Once or twice per year for the obligatory A-Chain. I the 8 years we've had it, I think the cards have been removed, maybe, 3 or 4 times.

I thought about the power supply. It's an external box that bolts inside the back of the sound rack. Right?
Both red LEDs were lit. In the process of checking the system I did unplug it and plug it back in again.

The movie's running right now. It seems OK through two shows today and one yesterday. At this point, I'm crossing my fingers and hoping it was a one-time thing.

I'm going to have to check into that contact cleaner. We've got lots of potentiometers and connectors that could use a bath!

Posted by Gordon McLeod (Member # 33) on 09-28-2005, 08:19 PM:

The DSP matrix in the mod2b/c can lock up and ditching the power will reset it

Posted by Dustin Mitchell (Member # 372) on 09-28-2005, 10:42 PM:

Yes, the power supply is the external box bolted inside the rack. The one I referrenced above gave no obvious signs of failure (lights out, etc).

Posted by Randy Stankey (Member # 64) on 09-28-2005, 11:23 PM:

Gord:

Aah! THAT matrix board!
Yes, we have one of those!
Do you think this board is more likely to wedge due to a line voltage fluctuation? We may have had one or more of them during the last few weeks. There have been some storms. Leftovers from Katrina and Rita. Although I didn't notice much in the way of lightning, I have a hunch that the wind in the wires may have caused some bumps.

Dustin:

Thanks for the tip! I did suspect the P.S. but, since the lights were both lit, I assumed it was OK. In other models the light(s) go out when the supply is bad.
Did you put a volt meter on it or anything like that? If these things die the way you say, it'd be nice to know.
Again, power surges are suspected. If one didn't wedge the matrix card it may have gotten the P.S.

In either case, do you all think this is one of those "slippery slope" type events? There might be one or two failures at first then they become more and more frequent until the thing finally gives its last gasp? In that case, I will need to get the spare parts. I don't have the luxury that many commercial theaters have. Where they can order parts from the warehouse and have them by Fed-Ex Overnight, it can take up to a week for me to get them. If I raise the alarm bells, I MIGHT be able to get parts overnight but it's a long shot.

If this may be the case, I will have to put that proverbial slip of paper in the takeup reel right now! [Wink]

Posted by Randy Stankey (Member # 64) on 10-01-2005, 11:36 PM:

Well, the problem surfaced again. This time the system went down in the middle of a show! (A concert, not a movie.)

Turns out it was the Media Matrix. One of the two BOBs (Break-Out Box)... The digital signal processing unit that handles the input and output. It died completely and put half the house's speakers out of commission.

However, we got lucky in three ways:

1) The concert didn't need all the output channels in our system.

The show was Ann Hampton Callaway. (Wrote and performed the theme from the television show, "The Nanny".) Backup was a big band on the stage. In our hall, a band like that didn't need much reinforcement. Reinforcement for the vocals was easily rerouted.

2) Our hired-in sound man is one of our regulars. He knows the sound board pretty well. Didn't take him long to get a handle on the situation.

3) Our sound system contractor was on-site. He was able to reprogram the remaining BOB to handle the rest of the load. Hooray for built-in redundancy! [Big Grin]

Although I don't think it 100% exhonorates the Mod II B, I think the main problem is solved. All of us are in agreement that it must have been a recent voltage spike that killed the system. It knocked out the BOB. That doesn't mean that it didn't weaken the cinema processor but I'm leaning toward Gordon's suggestion that the DSP inside the processor locked up.

I don't see how a spike that killed the BOB wouldn't have had SOME effect on the processor.

If I get any more news I'll let y'all know. But I think the solution is at hand. Replace the BOB and reprogram it.