On My Bench.

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Dave the bass
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#76 Re: On My Bench.

Post by Dave the bass »

Following on from above ^^^ Well, it was those caps that was causing the fault, the +5V rail is now restored and the USB Soundcard now works, whahey!

Next!

So I settled into my comfortable chair this morning to enjoy light discourse over fresh coffee with JTS when :shock: a Total utter hold-the-front-page earth shattering electronic emergency occurred. :shock:
:diabloanifire: <- haven't seen that one in a while....

This stopped working...
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Its a 24V DC PSU that powers the recline function on my chair. That means I can't recline into the usual 'intense-music-listening/resting-my-eyes' position.

A LOCAL STATE OF EMERGENCY WAS DECLARED.

On to the bench for pronto fault finding. I found the glass envelope of the T3.15A fuse soldered by end-caps to the PCB by the mains power connections physically blown apart. This didn't bode well, a fuse that size blowing in that fashion points to big instantaneous current draw, oddly I couldn't measure any low resistances but it was very difficult to visually check for signs of arcing or heat damage as a lot of the components were covered in a silicone rubber solution. Hmm, I chanced a temp replacement 20mm fuse wired into a makeshift fuse holder then carefully powered up to observe for localised lightning.

Not unsurprisingly, Erks..
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Saw summat close to the heatsink flash before the fuse blew again although there were no low resistances found around the semiconductors in that area, odd. I started hacking away at the white silicone sealant gloop....

I found this NTC device blasted in two, (featuring special manicure detailing for our-Simon)....
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...and further signs of arcing where a hole has been blasted through here as illustrated by the pointer...
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Aha! Found it. One leg of the big electrolytic cap has fractured and you can see where arcing has flashed across the pinout area of the cap...
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Right, thats too many safety critical components popped there for my liking so I'm not going to go further with a possible repair here so I'll order a replacement PSU.

In the meantime a handy bench PSU is supplying my chair tonight.
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And relax :)
"The fat bourgeois and his doppelganger"
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andrew Ivimey
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#77 Re: On My Bench.

Post by andrew Ivimey »

Happy ending then 👍
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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pre65
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#78 Re: On My Bench.

Post by pre65 »

Well done Dave.

Wanting to relax, and knowing how to relax are two very good traits. :lol:
The only thing necessary for the triumph of evil is for good men to do nothing.

Edmund Burke

G-Popz THE easy listening connoisseur. (Philip)
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MistyBlue
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#79 Re: On My Bench.

Post by MistyBlue »

Dave, that's the best nail art I have ever seen! :lol:
"When we're about to do something stupid, we like to catalogue the full extent of our stupidity, for future reference." - Commander Susan Ivanova, Babylon 5
simon
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#80 Re: On My Bench.

Post by simon »

Recliner no worky, very serious indeed. Excellent interim solution Dave :thumbright: .

I think you've let yerself go a bit there though, not as neat cutting as previously. It's to be expected though when faced with such an emergency.
Morgan Jones
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#81 Re: On My Bench.

Post by Morgan Jones »

Dave the bass wrote: Mon Feb 19, 2024 10:18 am Ta for your thoughts all, I was wondering if there were any specific characteristics that Tantlum caps had that electrolytic don't, or vice versa.
High ESR. (And very variable.) That's why they're recommended for regulators - the high ESR prevents a high Q resonant circuit forming. They're very fragile (low ripple current capability) and invariably fail S/C as you have found. But (unlike a wet electrolytic capacitor) they don't get any worse with age, so they're good for long service life stuff provided they're used carefully. That means no switchers. And they're small, which is why they turn up in portable equipment.
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Dave the bass
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#82 Re: On My Bench.

Post by Dave the bass »

Awesome, thanks for the Tantlum info Mr Jones. Yep, every Tantlum cap I've found failed in the past has gone short and occasionally physically cracked as in this case.

Glad my 'nail-art' is appreciated, I go to all the best places y'know :)

Next!

Study time, I've got my Foundation (Radio, not Cosmetics OK) exam at the end of this month so I'm getting stuck into these...
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Onwards.
"The fat bourgeois and his doppelganger"
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Mike H
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#83 Re: On My Bench.

Post by Mike H »

Re the PSU, wow what a story. :lol:
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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andrew Ivimey
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#84 Re: On My Bench.

Post by andrew Ivimey »

Yeah- noble effort and all but didnt he just buy another.
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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andrew Ivimey
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#85 Re: On My Bench.

Post by andrew Ivimey »

I go and get my camel...
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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Paul Barker
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#86 Re: On My Bench.

Post by Paul Barker »

Study time, I've got my Foundation (Radio, not Cosmetics OK) exam at the end of this month so I'm getting stuck into these...
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Im intermediate but I sold my rig
"Two things are infinite, the universe and human stupidity, and I am not yet completely sure about the universe." – Albert Einstein
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Mike H
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#87 Re: On My Bench.

Post by Mike H »

:thumbright:
 
"No matter how fast light travels it finds that the darkness has always got there first, and is waiting for it."
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Dave the bass
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#88 Re: On My Bench.

Post by Dave the bass »

Paul Barker wrote: Sat Mar 30, 2024 5:16 pm
Im intermediate but I sold my rig
Ah, I didn't know that. There's a few parallels with DIY HIFI I'm finding for sure.

I passed, I got my licence yesterday and now operate as M7IPY...'M7 Hippy ' 🤭

M7DTB had already been assigned as had PHP (pot head pixie), double meh!
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andrew Ivimey
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#89 Re: On My Bench.

Post by andrew Ivimey »

Congrats!!! M71PY
Philosophers have only interpreted the world - the point, however, is to change it. No it isn't ... maybe we should leave it alone for a while.
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Nick
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#90 Re: On My Bench.

Post by Nick »

Well done.
Whenever an honest man discovers that he's mistaken, he will either cease to be mistaken or he will cease to be honest.
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