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Old 6th August 2013, 05:32 PM   #13271
sangram is online now sangram  India
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Quote:
Originally Posted by Rixsta View Post
Also lol, say there was a fault, If one fuse blows then it would mean only one half of the AC would be working.
Which could make it so only the positive half of the power supply is working, so Im just wondering what would happen to the amp I presume it would be ok.
If the F5 misses a rail, it puts out a full-rail DC offset for a half second, and then the offset stabilises pretty close to zero and music plays just fine. There is some discussion on this in one of the posts on this thread.

Found out the hard way when one of the rail cables worked loose, my speaker took it on the chin and survived.
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Old 6th August 2013, 06:05 PM   #13272
lhquam is offline lhquam  United States
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Originally Posted by Rixsta View Post
Cheers!
Do we know if the Thermistors have to touch the metal washer or Mosfets ?
Im worried about touching it against the washer in-case It makes a short circuit, perhaps I should put a bit of Mica over the thermistor to insulate it ?
You should worry. I smoked my first F5 build due to a crack in the paint on a thermistor that caused a short to the MOSFET drain lead. In subsequent builds I have used thermal epoxy and a tiny piece of mica between the thermister and the drain lead.
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Old 6th August 2013, 06:26 PM   #13273
Rixsta is offline Rixsta  United Kingdom
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Hi, there is a CL60 NTC on the power in to primary of the transformer

vdi_nenna, my PSU has only a single centre tap wire so cant put the 2 NTC on.
Amp works fine i presume that just the inrush is blowing fuses.

udailey, I have fuses on the secondary one on each secondary wire before caps, I have 2 secondary green wires and 1x black centre tap. I have a fuse on the primary too before the thermistor. that was blowing too at 6A. Im on 240v here.
Ok i shall remove fuse on the rails and just have one main fuse on primary side.

sangram, yes when I was putting the oversized 13A fuses in I noticed one didnt go in properly. I ended up with the amp playing only the positive rail, as you say still played music but was half missing a bit distorted.
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Old 6th August 2013, 06:27 PM   #13274
Rixsta is offline Rixsta  United Kingdom
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Quote:
Originally Posted by lhquam View Post
You should worry. I smoked my first F5 build due to a crack in the paint on a thermistor that caused a short to the MOSFET drain lead. In subsequent builds I have used thermal epoxy and a tiny piece of mica between the thermister and the drain lead.
Exactly my point, this is my plan then, thanks and my washers fill the whole Mosfet so I cant lay the thermistor against it as all there is is washer.
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Old 6th August 2013, 06:40 PM   #13275
bcmbob is offline bcmbob  United States
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Originally Posted by Rixsta View Post
.......and my washers fill the whole Mosfet so I cant lay the thermistor against it as all there is is washer.
I'm not sure what you are describing. This pic shows two extra thermistors for a cooling system, but they all work well on the washer.
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Old 6th August 2013, 06:45 PM   #13276
Rixsta is offline Rixsta  United Kingdom
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Originally Posted by bcmbob View Post
I'm not sure what you are describing. This pic shows two extra thermistors for a cooling system, but they all work well on the washer.
Yes, no problem there mine looks like yours, i was going to have thermistor touch the black Mosfet case but cant as washer is massive so will have thermistor with a small slice of mica in-between.
I Don't want to make same mistake as post #13272
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Old 6th August 2013, 08:30 PM   #13277
Itsmee is offline Itsmee  England
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Quote:
Originally Posted by Rixsta View Post
Also lol, say there was a fault, If one fuse blows then it would mean only one half of the AC would be working.
Which could make it so only the positive half of the power supply is working, so Im just wondering what would happen to the amp I presume it would be ok.
There is a simple but effective way of protecting your speakers from large DC offset caused by a blown supply fuse, don't use them.

However this does not help in the case of a faulty amplifier or PSU; and that is where an appropriately sized polyswitch is useful.

Buy Resettable Wire Ended Fuses RHEF polyswitch resettable fuse, 0.5A TE Connectivity RHEF050 online from RS for next day delivery.
Resettable fuse - Wikipedia, the free encyclopedia

Fit the polyswitch in the 0V connection between star earth and connection back to the rectifiers or center tap of the transformer; most amplifiers are fairly symmetrical in +/- supply rail current consumption, meaning that very little current runs through the 0V connection back to the transformer; in the event of a fault, large currents will run through the 0V connection, tripping the polyswitch and preventing damage to your speakers.
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Old 7th August 2013, 11:20 PM   #13278
Rixsta is offline Rixsta  United Kingdom
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Realy ? that sounds pretty good!
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Old 21st August 2013, 02:05 AM   #13279
sjhomey is offline sjhomey  United States
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Default Only getting mono from my stereo F5

I finished the basic F5 a couple of years ago and really like the sound but felt that the imaging was lacking. Recently played it with a new pair of open baffle speakers for a friend and he said he thought the sound was mono. I got some test tones and sure enough when each channel was supposed to play by itself they both played and the sound was straight down the middle. So I started changing components and cables to isolate the problem. I tried an older receiver with similar results and then a third just for the heck of it and there was the stereo. At this point when using all my original setup, except the F5, I have stereo. It would seem that the F5 and also the second amplifier have a problem. I rebiased the F5, tried hooking up speakers out of phase, checked the star ground setup and as far as I can tell I have wired correctly. I am at a loss and wonder if anyone could give me some advice, aside from having my hearing checked so I might tell the difference between mono & stereo.
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Old 21st August 2013, 07:52 AM   #13280
Zen Mod is offline Zen Mod  Serbia
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