This is topic Strong SPA-7 fried in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=002951
Posted by Ian Price (Member # 14) on 01-11-2002, 06:12 PM:
There is a previous thread titled Strong SPA-7 Frailer that I started. In that case the problem was an old switch that had failed. Now that very same SPA-7 automation has failed in a more spectacular way.First the automation didn't work. So we checked the fuses and found one that was fried. It was the one right next to the power supply (3A 125V). We replaced that and turned the unit on. There was a buzzing sound and we switched it off again. The fuse wasn't blown so we turned the unit on to see if we could diagnose the problem. The failsafe wasn't on; it has a red light when it is in failed mode. Then we looked at the automation board again and it was smoking around the power supply, so we switched it off again and pulled the fuse. We are running in manual for now.
My next step is to contact my supplier and see if I can still get that board. Perhaps Pat Moore has a suggestion.
Meanwhile, do you have any suggestions?
Posted by Jerry Chase (Member # 660) on 01-11-2002, 06:28 PM:
Just one comment based on computer experience after lightning strikes. Once one component in a circuit has failed it can stress other components beyond their limitations even though those might last for a short while longer. I have no idea what the cause of the buzzing sound was, but I would suspect a bad bridge or power transformer that shorted windings? Beyond that, I'm out of my league and am equally interested to learn what the gurus have to say.
Posted by Ian Price (Member # 14) on 01-11-2002, 06:44 PM:
My Cinema supplier doesn't sell that automation. He threw a monkey wrench in my thinking by suggesting that the buzzing sound might be a relay being confused. He suggested that the failsafe might be sending an errent signal back to the automaion.The failsafe is a Strong FP-350 optical failsafe and proximity cue detector unit.
Having him say that just complicated the whole thing. We'll see what Strong has to say on Monday.
Posted by Gordon McLeod (Member # 33) on 01-11-2002, 07:47 PM:
I have had a voltage regulator fail on them
Posted by Pat Moore (Member # 380) on 01-11-2002, 08:56 PM:
Ian;I'm not the tech guru type guy, but it sounds like the power supply section of the automation has a severe problem. Look for shorted diodes in that area -- there will be four diodes that make up the rectifier bridge. There's also a capacitor of some kind in that same area, and I think there is a voltage regulator as well as Gordon says. I'd bet on the cap first, then the diodes -- failures there could have taken the voltage regulator as well. Check the foil traces in that area too -- something should look cooked. I doubt if it has anything to do with the failsafe, but you can disconnect it easily enough to prove that idea.
What failed before on this guy? Could there be a relation between the two failures?
We do still support the automation, but that might mean replacing the full board.
Good luck...
Pat
Posted by Dave Macaulay (Member # 813) on 01-11-2002, 09:07 PM:
SPA-7 ... This is likely a power supply problem. Unfortunately Strong supplies the most useless drawings ever for the SPA-7. The power supply (and a LOT of other stuff) isn't there at all.
I think Eprad made the thing, maybe they can help if you need info. If this is a wall unit it's not bad to work on, the X-90 console mounted ones are a bear.
The power supply is fairly simple. The buzzing suggests AC is getting through the supply (this makes the DC relays buzz) so probably a diode or bridge has failed. If you can tell what was smoking that will be a good clue.
It's unlikely that the cue/failsafe is the problem, but who knows? Try disconnecting it.
Be careful working in there, it switches 120VAC for the motor, lamp, and changeover and possibly a slide projector too. If it's an X-90 then turning off all the breakers except main and "automation" should remove all 120 (except the automation itself) but I wouldn't bet my life on it...
If it is a power supply failure, the electronics are fairly robust and shouldn't have failed. The power supply parts are all standard stuff (except the transformer) available at Radio Shack type places. Hope for the best! If some of the main circuitry has failed, most of the tricky stuff uses programmed logic chips that will only be available from Strong.