yamaha stagepas 300 problems

Posted: Mon Jul 24, 2006 10:09 am

Hey everyone. I use a Yamaha Stagepas 300 system for a musical theater show. We run the show every week. The system works well and fills every hall we play very well.

Connected to the Stagepas's mixer are 3 wireless microphones and an MD player.

The trouble we are having is that sometimes the sound just drops out. There is a small pop and then no sound at all. The mixer is still on and the LED's are showing signals to the mixers's pre-amp. The LED's on the mic tranceivers are reading a signal. Shutting off the mixer and turning it back on can solve the problem sometimes. And sometimes it just shuts off again. The unit has gone back to Yamaha to be inspected twice. They found nothing wrong with it and sent it back to us.

Now, this is all taking place in Japan, where I live and work.

The microphones are Maxons and the wiring is good quality Canare. We are never running the system near its limits. It is never very hot.

I do not know what the topology of this amp is. I would assume it is a switching amp of some kind since it is very small and light. Also, we plug directly into the wall socket of the halls that we use.

I wonder if a sagging AC current would cause this kind of problem with some amp types. The class A/B amps we used before did not have these problems. We bought the Yamahas to test them since they are lighter and easier to set up. We ship these things all over Japan by truck freight.

Anyone have any ideas of what is going on here with this amp? Any advice or similar stories? Need some help on this one. Yamaha Japan is not being particularly nice or supportive at the moment.

-Shawn

Posted: Mon Jul 24, 2006 9:23 pm

What you describe could easily be due to a brownout and/or the PA is overheating and the built in thermal shutdown is active. Do you have too many speakers connected or are you running lower than 4-ohms? Does the amp head get really hot? Make sure it is getting good airflow all the way around it and maybe even try to put a fan directly blowing on the on the power amp or heat sinking fins.

Posted: Tue Jul 25, 2006 12:07 am

Neither of those are an issue. The Stagepas 300 comes with its own speakers. We are using those. The amp is stand-alone, on a table. It has a cooling fan and it is never hot to the touch. The one, small cooling vent is on top of the mixer-amp and is not blocked. There is nothing placed on top of the amp.

Again, we never run it anywhere near full volume. The MD players' "idea" of unity gain is a bit funny. It is a tad lower than the Tascams we used before. So, the MD player (connected by RCA cables) is turned up a bit on the volume pot concerned with the "Line In" section. Sometimes we have it up to 80% or so. The master volume never leaves 70% (hash mark on the amp itself).

The amp is a piece of molded plastic and metal. There are no external heat-sinks.

-Shawn

Posted: Tue Jul 25, 2006 9:22 am

Hi Shawn.

I have seen the Stagepass 300 and was tempted by it for a production. Things turned out differently so I did not buy one. To me it looked like a capable system in a small package. I did not really like the sound of the built-in fan in the demo unit I saw, it had probably been knocked around a bit. Probably easy to fix.

Regardless, the box has a class D amplifier (not digital really, class D is still analog components). These can create a lot of volume in a small package as they create very little heat. I would guess it has a fairly sophisticated thermal shutdown system though to protect it. My guess is that this is what happens to the system - some part of it gets above the temperature treshold and it shuts itself down. The heat fins as I remember it are probaly only inside the unit.

It is odd that Yamaha could not fix the problem though, it should be rather easy to fix.

What I suggest is that you start searching for the caues:
- shaking the box thoroughly but not violently. There might be loose components or even small pieces inside the box that shorts things out.
- try blocking the air path (gaffa might be the way to go) to see when it turns off itself. Carefully watch what happens and compare.
- visit an electronics shop and ask for "cold spray". You might use simple compressed air instead. Next time the machine stops, put the outlet inside the machine and swoosh it in cold air. If it starts immediately the culprit most likely is the temperature protection.

Once you know it is the temperature protection, check things like that the fans moves freely and blows air. There might be restrictions in the air path.

At the end of the day, my guess is that you have a faulty individual of the amp unit. I would try to use a bit of persuasion to try to get it exchanged if at all possible.

Anyway, my two cents and a few ideas.

Below is the Sound-on-Sound review.

http://www.soundonsound.com/sos/mar06/articles/live_stagepas.htm

Gunnar

Posted: Thu Jul 27, 2006 7:25 am

Thanks for the advice. I will check those things out. As for Yamaha, they claim that they have checked out the unit for 24 hours and it is perfect. I would assume that, had they done that, they would have opened it to check for faulty/loose components. The truth is, I do not believe that they actually checked out the unit.

This is only happening with one unit. We run about 7 stagepas 300s in different parts of the country at any given time. The other 6 have experienced no trouble.

One of the sound people mentioned that she "kicked" a cable or power cord and the unit shut off. So, we will first replace all power cables and cords. I will then go through the sequence outlined above if that does not solve the problem. The one problem is that the boxes containing the amps don't always come back through Tokyo en route to their next destination. I can only diagnose on a day when I need the damn thing to work. Well, we will give it a go. Thanks for all the good advice!

If anyone else has any ideas, please shout 'em out!

-Shawn

Posted: Fri Jul 28, 2006 1:29 am

Alladin, if someone kicked a cable and the unit shut off, there's a good chance they may have damaged the speaker output jack or some other jack. When jacks and controls are soldered directly to PC boards the result is a less than roady-proof unit. I would guess the problem is not your cables but a damaged or intermittant pc board. Another likey suspect is a cracked pot caused by a hit to one of the controls.

Since you move your stuff alot I would expect that it took a hit in a sensitive area. Unless your a qualified tech I would take it to a tech for repair.

Good luck
gb

Posted: Sat Jul 29, 2006 10:41 am

Everyone, thanks for the great advice.

Guitarbill: The "kick" happened before we sent the units to Yamaha the first time. They said that they checked out our unit for 24 hours. It came back with a clean bill of health. They are shipped around. The amp/speakers are shipped in padded, custom-made boxes. However, I have seen Akabou and Sagawa (roughly UPS-like companies) drop the boxes on occasion. Our boxes are a bit special. They are 5-7 layers of corrugated cardboard box epoxied together and then completely wrapped in plastic tape (think: a box in a box in a box...etc.). The result is a light box that is strong enough for 3-4 people to sit or stand on. We stand on these boxes (empty) all the time. It also has good shock-absorbing capability when dropped.

We may send it back and I will insist that they check on the Jacks and the jack-PCB connections. This actually was a problem with a different brand of amp that we used before.

-Aladdin

Posted: Mon May 21, 2007 4:31 am

Hi everyone
I've just signed up to recording, and read about Aladdinn's problem with hes Stagepas 300 P.A. I've had the same problem on and off for eighteen months mow and its driving me crazy. We use two guitars, two mics and a C.D. player through it, sometimes it works perfectly and then when you're confidence is high, without warning the sound just cuts out conpletely. I returned it to Yamaha last November and they done a 24hr soak test and couldn't find anything wrong with it so th be on the safe side they replaced the two amp modules and the two fans, since it was returned we used it on five gigs and it worked perfectly then last Saturday it cut out twice after only five mins we managed to go on for another forty five nins(not very confidently) and it went again and again and again forcing us to take a early break, after the the break it worked alright for the rest of the evening, its fust as if someone had rulled the speaker cables out, everything else was showing normal no limiter lights and not over heating as it was only working for five mins before it failed, hoping someone can help me before I go off my head.
Hoping with anticipation

Phoenix

Posted: Mon May 21, 2007 4:33 am

Hi everyone
I've just signed up to recording, and read about Aladdinn's problem with hes Stagepas 300 P.A. I've had the same problem on and off for eighteen months mow and its driving me crazy. We use two guitars, two mics and a C.D. player through it, sometimes it works perfectly and then when you're confidence is high, without warning the sound just cuts out conpletely. I returned it to Yamaha last November and they done a 24hr soak test and couldn't find anything wrong with it so th be on the safe side they replaced the two amp modules and the two fans, since it was returned we used it on five gigs and it worked perfectly then last Saturday it cut out twice after only five mins we managed to go on for another forty five nins(not very confidently) and it went again and again and again forcing us to take a early break, after the the break it worked alright for the rest of the evening, its fust as if someone had rulled the speaker cables out, everything else was showing normal no limiter lights and not over heating as it was only working for five mins before it failed, hoping someone can help me before I go off my head.
Hoping with anticipation

Phoenix

Posted: Mon May 21, 2007 11:38 am

It your problem appears after being used for a period of time and then goes away after a break or a period of time, then it would indicate some sort of heat problem. Most over load lights just tell you when you are overloading or clipping the input and/or when you have used all available headroom and don't really give you any accurate heat temperature indication. The fact that the fans and amp modules were replaced is another sign that there is very likely some sort of heat related problem or maybe even a design flaw with the product which would mean that no repair may ever get the product to be fully reliable. Yamaha may already be aware of the exact issue and are dealing with the existing problems as they have to which may even include denial, as it is sadly a standard practice with mass produced gear makers.

If it were me, I would find a way to sell, or demand a refund, or at least a whole new recent made replacement product.

Posted: Sun Nov 04, 2007 8:15 am

I have had the Stagepas 300 for about 18 months, gigging regularly, with no problems ...until recently. I started experiencing the same problem as described in this thread with the sound cutting out. It wasn't the limiter cutting in, the fan was OK and the air flow good etc etc. Thinking what had changed I realised that a few weeks ago I had upgraded the speaker leads, as until then I had still been using the speaker leads supplied with the stagepas. The only reason I changed was that I wanted shorter leads.

To cut a long story short, going back to the original leads has resolved the problem.

As long as I use the original leads to connect the speakers it appears that all is well. As soon as I use anything different the problem comes back (I've tried this with several leads - all of which check out OK on other gear, so the leads aren't faulty - but the Stagepas doesn't like them.)

So, if you experience this situation try going back to the supplied (cheap) leads to see if this resolves the problem.

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