Deleted
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Post by Deleted on Nov 22, 2020 16:05:39 GMT
Any ideas on what would cause a recently sbipped monoblock Mod-86 amplifier to cut out during use?
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Post by firebottle on Nov 22, 2020 16:54:21 GMT
Overdriving, too low a speaker impedance causing current limit to activate?
More details of the conditions before cut out needed.
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Post by Deleted on Nov 22, 2020 17:15:46 GMT
I have asked Dave for some more details.
Quite concerning, as I never had an issue with these, and my speakers dip down to 3 ohms.
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Post by sq225917 on Nov 22, 2020 18:01:31 GMT
They have over voltage, current and thermal limiting built into the chip.
Turning the volume down will fix the last two, but have no effect on supply over voltage.
The supply voltage should be reduced if driving low impedance speakers.
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Post by emmings on Nov 22, 2020 18:14:40 GMT
Hi all - here's possibly some overkill in details of the system/environment and the problem I've experienced.
I will be moving things around in the rack/environment tomorrow and do some more testing/listening.
One of the monoblock amps cut out on me a few times - the first time after about an hour of playing. It would come back after being switched off but only for a few minutes.
The amp doesn't feel hot anywhere on the case and the power light was lit quite happily - but no sound. I switched XLR cables around and speaker cables - but it seemed it was just this one amp that was silent.
There was no smoke/pop/flash or anything untoward - the amp just cut out.
I did have the amps sat on a wooden block quite close to each other - about an inch apart and like this the left hand one would cut out.
There was a gap of about 3 inches to either side of each amp – so basically, they were in an enclosure which is open to the front and back but surrounds the amps.
I have since moved them apart - the one that cut out is now on a granite tile about a foot in front of the other. When set up like this it's been playing quite happily for about 25 minutes with no problems. In fact, like this they’ve been quite happy for just over an hour.
All the equipment I use has been built by other people since I have no DIY equipment skills 😊
I am using a DCB1 pre-amp which uses a Hypnotize DC B1 Jfet buffer with a Valab 50K stepped attenuator which I use at around the one o’clock position.
The speakers are Wilmslow Audio Gemini with the following specifications (copied from their website):
Treble: Morel CAT308
Bass-mid: Morel CAW538 (x2)
Frequency response: 40Hz - 22000Hz
Sensitivity (2.83v/1m): 91dB
Amp requirement: 30-150w
Impedance: 4 ohm
These use an external cross-over – again built by someone else and unfortunately, I don’t know the specs of these.
The speaker cables are Bigbottle Audio Spotfire.
The interconnects from the preamp to the amps are RCA->XLR using Van Damme Pro Grade XKE Oxygen Free Copper Dual Screened silver plated cable with Neutrix connectors.
I’m using a Puritan Audio PSM156 mains purifier with a variety of mains cables.
The mains cable to the amp which experienced the problem consists of Oyaide EE/FS-2.6mm solid core cable terminated with Furutech FI-UK mains plug and a Furutech FI-11 gold plated IEC.
I’ve since swapped this over with the other amp for an MCRU power cable (not sure what version).
The whole rack is about 2 and a half feet from a radiator.
So – 2 monoblocks, same connectors, same speaker cables and 2 different power cables. One has experienced cut outs – the other has been fine.
Kevin had been very helpful over the whole thing and I am more than keen to keep hold of these and find a solution.
Since the original problem occurred and moving them apart and switching the power cables around they’ve performed perfectly. Weird 😊
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Post by karma67 on Nov 22, 2020 18:19:49 GMT
easiest thing to do is put them back close together and see if it starts again,if it does you've found your problem  |
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Post by Deleted on Nov 22, 2020 18:34:54 GMT
easiest thing to do is put them back close together and see if it starts again,if it does you've found your problem They sat pretty close together when I had them, and worked flawlessly. This is the most annoying thing about this... |
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Post by emmings on Nov 23, 2020 12:39:01 GMT
Update time
I've moved things so the monoblocks are seperated from each other and with good airflow.
Unfortunately the one monoblock (let's call it 'A') playing up yesterday is still having problems. It was running fine for an hour or so yesterday afternoon - no problems but this morning it's refusing to play.
Started playing a track and there was about a minute of music from both channels and then 'A' stopped playing - no music from one channel. It did try to chime in again a couple of times but then refused to play ball.
Wondering whether I have a duff power cable I swapped it out for a generic kettle lead - no joy. Switch on - a few seconds of music then nothing.
Replugged the amp in to another socket - same story.
Swapped the monoblocks from left to right - and 'A' still plays nothing.
So one monoblock works fine and one seems to be working intermittently in that you can switch it on and it's fine then after 10-15 seconds it stops.
And just as I'm typing this it's chimed back in - I'd left the music playing whilst typing and it came back on. And then it's stopped again - coincidentally just as some drumming kicked in (playing Ozric Tentacles - The Domes of G'Bal).
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Bigman80
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Post by Bigman80 on Nov 23, 2020 13:23:30 GMT
I wouldn't recommend that they continue in service for now as you don't know what's happening. Don't want to make it worse. See if firebottle will give them the once over for you. |
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Post by emmings on Nov 23, 2020 13:32:27 GMT
I have kept them playing and after switching off for 5 minutes earlier the problematic amp has started playing again. It did play for 10 minutes, then cut out and now it's back to playing again. I have no electronic expertise but is it possible (and I appreciate 'remote' diagnosis is not 'recommended') that a connection in the power supply has intermittent problem (loose wire?/solder)? I'm trying to get hold of a mate who is an electronics engineer by trade and is local to give the offending article a look over. And it's just cut out again - will switch off now  |
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Bigman80
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Post by Bigman80 on Nov 23, 2020 13:40:12 GMT
I have kept them playing and after switching off for 5 minutes earlier the problematic amp has started playing again. It did play for 10 minutes, then cut out and now it's back to playing again. I have no electronic expertise but is it possible (and I appreciate 'remote' diagnosis is not 'recommended') that a connection in the power supply has intermittent problem (loose wire?/solder)? I'm trying to get hold of a mate who is an electronics engineer by trade and is local to give the offending article a look over. And it's just cut out again - will switch off now It may be possible, but more likely to need a bit of "hands on" investigation. |
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Post by emmings on Nov 23, 2020 13:47:41 GMT
Totally agree - just doing the usual 'wondering' what's going on.
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Post by Deleted on Nov 23, 2020 14:02:43 GMT
I am really dissapointed to read that they are playing up.
I can only assume that they have suffered from shipping. I thought I had wrapped them up safely enough.
I really hope that this is an easy fix.
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Post by emmings on Nov 23, 2020 14:13:01 GMT
Certainly wouldn't fault the packaging - that was top notch. And undamaged/intact on receipt.
Can only suspect something happened during transit that may have 'nudged' something out of kilter.
Sound excellent though!
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Post by Deleted on Nov 23, 2020 14:14:51 GMT
It can only be something that happened during the transport. They were 100% when they left here.
Please keep me updated on this.
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Post by firebottle on Nov 23, 2020 15:31:55 GMT
I would look for a loose joint/wire or even a 'loose' fuse.
Also make sure the '86 chip is securely bolted to the heatsink, it could be that simple.
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Bigman80
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Post by Bigman80 on Nov 23, 2020 15:50:12 GMT
Certainly wouldn't fault the packaging - that was top notch. And undamaged/intact on receipt. Can only suspect something happened during transit that may have 'nudged' something out of kilter. Sound excellent though! Send a BB3 to Australia. Got there broken somehow even though it worked perfectly here. Thankfully I sent the fella a video of it working. It's on its way back to me for repair It happens! |
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Post by Deleted on Nov 23, 2020 16:19:53 GMT
I just hope that the FB Monos that arrived with their new owner today have faired better in transit.
These were in similar bomb proof packaging.
Time will tell....
I really do hope that the fix is simple. They are great little amps, when working.
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Post by Deleted on Nov 23, 2020 16:23:24 GMT
I just hope that the FB Monos that arrived with their new owner today have faired better in transit. These were in similar bomb proof packaging. Time will tell.... I really do hope that the fix is simple. They are great little amps, when working. Just got a PM from a happy new owner. One less thing to worry about. |
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Post by Deleted on Nov 23, 2020 18:55:41 GMT
Looking at these amps, I am wondering if Dave would be happy popping the lid off the offending amplifier to see if there is a wire loose in one of the screw terminals, or as Alan says, the chip is no longer securely bolted to the heat sink. I guess it may have vibrated loose in transit. If we had a photo of the inside, we may be able to see what the issue is, but they need to have been unplugged for a while before you do. Just look at all those capacitors.... I am guessing from the problem description that it is either the power connector to the amp board, or as Alan says, a loose fuse, or the chip not being installed properly. The LED is powered from the PSU board, so the issue has to come from the other side of the amp. I can understand if you don't want to do it Dave. This is what they looked like when built. I never took the lids off.   link |
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Post by sq225917 on Nov 23, 2020 19:04:26 GMT
Pics would be good. Id be measuring the mains voltage and the dc voltage coming off the back of the psu cap board as well.
Itll be an easy fix, they're rock solid bits of kit
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Post by emmings on Nov 23, 2020 19:09:22 GMT
Should be easy enough for me to do - probably the limit of what I can though Unit is now unplugged - I'll leave it alone overnight and take the lid off tomorrow and get a few photos and visually check if anything is loose. As Bigman80 said - these things can happen but at least you guys are helping source a solution. This is appreciated. |
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Post by Deleted on Nov 23, 2020 19:12:49 GMT
It is the least I can do.
I appreciate the help and support form the others on here.
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Bigman80
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Post by Bigman80 on Nov 23, 2020 21:37:20 GMT
Yup, that's what we're all about here....helpful souls.
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Post by emmings on Nov 24, 2020 13:57:01 GMT
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Post by sq225917 on Nov 24, 2020 18:32:47 GMT
Id nip up the chip and the screws on the green terminals before you ship em off. I had to tighten the 3x block from the psu on mine after six months, one screw had backed off a little over time.
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Post by emmings on Nov 24, 2020 18:56:01 GMT
Evening.
I checked the chip screw and the green terminals - all felt tight enough to me and certainly weren't loose. Didn't want to force them any further just in case...
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Post by Deleted on Nov 25, 2020 8:32:50 GMT
Just wondering if the LM3886 chip is faulty. Maybe the 4 ohm speakers have pushed it more than I ever did with my 8 ohm nominal speakers?
The good news is that these are relatively cheap.
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Post by firebottle on Nov 25, 2020 8:58:27 GMT
Would you like me to take a look at it?
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Post by emmings on Nov 25, 2020 10:00:45 GMT
Would you like me to take a look at it? This is very kind of you. At the moment it's being checked over by an electrical engineer friend who has a workshop down the road from me. Should he be unable to track down the problem then I would be more than grateful if you could have a look at the unit. |
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