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Spot the deliberate mistake

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kedwardsleisure View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2021 at 11:54am
Rather costly 'mistake' if anyone fancies a go. A picture of half an easter egg with teethmarks in it for the first to guess correctly.

Client bought a pair of powered studio monitors off ebay, sold in good order.
I might have the details a little in the wrong order or missed out the finer points... but essentially he tried them on an ipad. They worked fine. He then tried them on his iMac desktop studio setup through a USB audio interface. The iMac went up in smoke. Went off for repair, was told the motherboard was 'fried'. Expensive repair. Sent the interface to the manufacturer who gave it a clear bill of health.

Here are the mucky pics of one of the monitors.





Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2021 at 12:13pm
Easy!!

It looks like the Chips doing power amp duty, bolted to the heatsink, have been "molested", from the way the paste is messy. I would guess their tab carries a voltage, which has not been correctly isolated from heatsink.

Heatsink is bolted to PCB, via bolt with red sealing varnish on it, conveying this Tab Voltage to "earth"/0V. 0V on an iPad "floats" or has a DC blocking cap on I/P. MacBook doesn't have DC blocking cap on USB input? Poof!
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
"Sparkius metiretur vestra" - "Meter Your Mains"
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kedwardsleisure View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2021 at 12:46pm
This question is for everyone apart from Matt
Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote MattStolton Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2021 at 12:58pm
The giveaway was the paste, looked sloppy. Then you look and can see different "shades" of grey of solder, and you know someone has been in before you.

When you realise that, you are suddenly filled with the dread of having to fix the original fault, and the fault caused by previous "Engineer"...

Typical that my first reading of a post on the forum in 4 months was this one!! Sorry, next time I will shut up, and let someone else have a go first. Just feel so out of practice, what with Furlough and stuff.
Matt Stolton - Technical Director (!!!) - Wilding Sound Ltd
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kedwardsleisure View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 07 April 2021 at 2:23pm


-24V DC coming out of the XLR socket.
What gets me is that someone knew enough to change the amp IC but not enough to know the funny little thing that fell on the floor was an insulating washer

Edited by kedwardsleisure - 07 April 2021 at 2:25pm
Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 11:12am
caption competition....

Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jazomir Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 11:46am
Electrical widow maker.
Regards

Jazomir
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 12:12pm
"Sure mate we can have a link up, here's a power lead for your Soundlab rack"
Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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Post Options Post Options   Thanks (0) Thanks(0)   Quote njw Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 12:22pm
 'Put yer tongue on this....'
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Robbo Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 12:22pm
"NO"--You are not shoving that up my fanny!!!!!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 1:00pm
Aaah - I see ... you play death metal !
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 13 April 2021 at 1:08pm
That cable has it's uses.

Say the power in your house goes down. Plug the Cetac end into a generator, the other into a 13A socket - and voilĂ  - your house has power again!

LOL LOL LOL


Earplugs Are For Wimps!
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