Bryston 9B SST Shut Itself Off Mid-Movie...Why?

guest1121 · « **on:** 4 Feb 2004, 04:05 am »

As the subject indicates, I was watching a movie tonight, and right in the middle of it, my 9B SST shut down. I am not sure why it did this, nor am I confident I understand what caused it. I'm hoping someone on this forum can help me answer these questions. Here are some specifics & background info for anyone who would be willing to help me figure this out.

Equipment & Configuration[/u]

Processor: Lexicon MC-12B
Amps: Bryston 4B SST; Bryston 9B SST

Both amps are powered on by the trigger outputs of the MC-12B. I have both amps plugged directly into one standard wall outlet (I don't know the amperage but it's a builder-grade outlet & circuit). The MC-12B is plugged into a surge suppressor.

The 4B SST powers the front left and right speakers, while I am using three channels of the 9B SST to amplify the center channel and side surrounds.

All equipment is installed in a standard floor-standing 19" equipment rack on mountable shelves.

The Situation / What Happened[/u]

Right in the middle of my movie tonight, the 9B SST shut itself off. After powering down all equipment, I wheeled out the rack and checked the back of the amps. I noticed that the master circuit breaker switch was NOT tripped; in other words, it was still set to the "ON" position. I flipped it off, then flipped it on again. That seemed to fix the issue; the amp came back on when I powered up the MC-12B and I had no further problems for the duration of the movie.

Despite the fact that everything seems to be working fine at the moment, I am concerned about what happened and I can't help but wonder why the amp shut off and whether it may happen again. My first thought was that I experienced a slight power overload and the amp went into auto-protect mode and shut itself off. But if that were the case, why wouldn't the circuit breaker have tripped?

I should also note that I played the entire movie at -20 Db...hardly a high-enough SPL to cause either of the amps to even break a sweat (neither was very warm to the touch). I gave the trigger wires a slight tug and they seemed snug to me, so I don't think a wire is loose.

Closing Thoughts & Questions[/u]

This incident leaves me with these questions:

1. Can anyone here help me understand why this happened?
2. Is there anything wrong with my amp?
3. Is there anything I can do to prevent this from happening again?

Thanks in advance for any help fellow owners and Bryston employees can provide me!

James Tanner · « **Reply #1 on:** 4 Feb 2004, 02:27 pm »

Hi Scott,

Have not heard of this before but it could be a drop in the power line voltage coming into the house. There is a sensing circuit in the 9B which turns the amp off if voltage drops below a specific point.
I will pass your comments on to engineering though in case they have any thoughts on it.

james

Eric · « **Reply #2 on:** 4 Feb 2004, 03:42 pm »

I have the 4bsst and this is never happened.

James Tanner · « **Reply #3 on:** 4 Feb 2004, 04:53 pm »

Hi Eric,

The 4B does not have the sensing circuit.

james

James Tanner · « **Reply #4 on:** 4 Feb 2004, 08:45 pm »

This response is from the Bryston US Service Center in Vermont. There are two possibilities here:

1) That amplifier employs a line-voltage threshold circuit which prevents the amplifier from being turned on if the line voltage is too low, and will also turn the amplifier off if the line voltage dips to a very low level when the amplifier is on. You might have had a power glitch that shut the amplifier off -- at the end of such a glitch, the amplifier will cycle on again if the "auto/local" slide switch in back is set to "auto." It's also possible that the threshold circuit is mis-adjusted, causing the amplifier to turn off with relatively small dips in line voltage.

2) We have had reported to us a couple instances of spontaneous turn-off in early 9BSST's, but we've not been able to reproduce the problem at our facility -- and so don't know the exact cause. However, the problem (if there is one) is going to be in the start-up board, no question.

Our suggestion would be that you go on using this and see if the problem recurs (also, make sure the "auto/local" switch is in the "auto" position). If the problem recurs, you may send the unit to us and we'll replace the entire startup board under warranty. If and when you decide to send it in, email us at usaser@bryston.ca <mailto:usaser@bryston.ca>.

guest1121 · « **Reply #5 on:** 4 Feb 2004, 10:12 pm »

James,

Thanks for the quick response. I'll keep my eye on it and see if it happens again, and if so, I'll send the amp in for a new startup board.

I guess it could have been a momentary lapse in voltage, but I have my doubts as I've been using this amp for over 6 mths. with no prior occurrences. Still, you never know!

I have the "External Power-Up" switch set to "Auto" and the "External Turn-On" switch set to "Remote" because this was the ONLY combination that would cause the amp to turn on when I powered up the MC-12B, and to turn off upon MC-12B power-down. Is this switch combination correct? From your email, it almost sounded as though it doesn't matter which setting the "External Power-Up" switch is in, but that hasn't been my experience.

Regardless, the unit did not turn itself back on after randomly powering off and I'm not sure why. I had to turn off the master circuit breaker and then turn it back on again. How long does the amp typically wait before cycling back on (I'm wondering if I needed to wait more than the few minutes I did)?

Assuming something in the startup board is faulty, does this in any way affect performance of the amp (aside from the random power loss issue)?

Thanks!

guest1121 · « **Reply #6 on:** 10 Feb 2004, 02:44 am »

Quote

...It's also possible that the threshold circuit is mis-adjusted, causing the amplifier to turn off with relatively small dips in line voltage.

2) We have had reported to us a couple instances of spontaneous turn-off in early 9BSST's, but we've not been able to reproduce the problem at our facility -- and so don't know the exact cause. However, the problem (if there is one) is going to be in the start-up board, no question.

Our suggestion would be that you go on using this and see if the problem recurs (also, make sure the "auto/local" switch is in the "auto" position). If the problem recurs, you may send the unit to us and we'll replace the entire startup board under warranty. If and when you decide to send it in, email us at usaser@bryston.ca <mailto:usaser@bryston.ca>.

James, if I send the amp back to have the entire startup board replaced, will putting in a new startup board also fix the threshold circuit, in case it's misadjusted as you suggest above? Tonight I had another "dropout" with the 9B. This time, it came back on after a few seconds, but I'm beginning to think I should send it to Bryston Service.

Thanks,

nicolasb · « **Reply #7 on:** 10 Feb 2004, 10:40 am »

Scott, sorry if I'm being obvious, but short-term drop-outs might be caused by the amp starting to overheat. Could that be the problem?

James Tanner · « **Reply #8 on:** 10 Feb 2004, 12:56 pm »

Hi Scott,

Yes the threshold circuit is part of the startup board so replacing it should take care of things.
If the amp overheats it will be per channel and the green LED will go yellow and shut off and cool down.

james

guest1121 · « **Reply #9 on:** 10 Feb 2004, 03:41 pm »

Quote

Scott, sorry if I'm being obvious, but short-term drop-outs might be caused by the amp starting to overheat. Could that be the problem?

Thanks for the idea, but this isn't it. As James as said, there are some indicators of overheating, but in addition to those, I've been playing movies at very low SPLs and even have put my hand on the amps - barely even warm to the touch.

James, thanks. I think I'm going to email customer service and arrange to have the startup board replaced. I really appreciate your help!

guest1121 · « **Reply #10 on:** 13 Feb 2004, 10:09 pm »

FYI - Well, the 9B shut itself off again two nights ago and would not come back on, so it looks like I'll be taking James' advice and sending it back to the factory for repairs.

James Tanner · « **Reply #11 on:** 14 Feb 2004, 01:43 pm »

Hi Scott,

Spoke with the engineers on this issue on Friday and we are anxious to see what is happening with your amp. Let me know if you need any assistance.

james

guest1121 · « **Reply #12 on:** 14 Feb 2004, 03:10 pm »

Thanks James; I really appreciate your help. I'm sure you saw the email I sent to Bryston Service late yesterday (I copied you on it); I'm awaiting further instructions from them but I understand it's the weekend, and perhaps the shop is closed on Presidents' Day. So, I'll look for a response on Tuesday.

Thanks again for your assistance!

briguy_78 · « **Reply #13 on:** 23 Aug 2007, 12:45 pm »

I have also experienced the same problem with my 9BSST. The only way I can get it to restart is to manually flip the power switch or in some instances unplug the amp and then turn it on. I was told that it was probably the soft start board and would ned to send it in for repair.