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Post by alit on May 6, 2021 16:52:07 GMT
Picked up a KSA 100 MK 1 in very good nick today, very pleased with it. Of course, once I got it home I had to get it's top off for a good going over.. Good job I did, first noticed the Zobel connection on one of the positive speaker posts had come adrift, and whilst I was doing that, noticed that some utter idiot had taken the speaker protection fuses out of circuit. Who the hell does that on an amp with this capability?? Did he think it would sound better or something.. Other than that it looks in great original condition. Anyone have a service manual?   |
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Bigman80
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Post by Bigman80 on May 6, 2021 17:02:13 GMT
Picked up a KSA 100 MK 1 in very good nick today, very pleased with it. Of course, once I got it home I had to get it's top off for a good going over.. Good job I did, first noticed the Zobel connection on one of the positive speaker posts had come adrift, and whilst I was doing that, noticed that some utter idiot had taken the speaker protection fuses out of circuit. Who the hell does that on an amp with this capability?? Did he think it would sound better or something.. Other than that it looks in great original condition. Anyone have a service manual? Oh man, that pulls on the "I miss mine" heartstrings!!! Beautiful amplifier. |
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Post by alit on May 6, 2021 17:19:38 GMT
Cheers Oli, yeah its in really good condition, very happy with it.
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Post by firebottle on May 6, 2021 17:37:29 GMT
.. noticed that some utter idiot had taken the speaker protection fuses out of circuit. Who the hell does that on an amp with this capability?? Did he think it would sound better or something.. Simple answer is yes. The output fuse will give a variable small resistor value depending on output power level, which will affect the damping factor. Not sure I would take it out though. |
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Post by alit on May 6, 2021 18:20:31 GMT
No me either. Can you remember Alan, is the fuse just in line with the pos speaker output?
It's a 6A fuse, so fairly hefty.
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Post by firebottle on May 6, 2021 18:58:11 GMT
Yes I believe so.
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Post by alit on May 6, 2021 19:29:43 GMT
OK thanks Alan.
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Post by sq225917 on May 6, 2021 23:55:50 GMT
I'd take the fuse out, and a properly designed none invasive protection board in there instead. Money well spent.
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Post by alit on May 7, 2021 5:26:13 GMT
Yeah had already considered that when I first agreed to the sale. Talked to Nick about it, he was of the opinion not to bother.
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Bigman80
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Post by Bigman80 on May 7, 2021 5:34:39 GMT
Yeah had already considered that when I first agreed to the sale. Talked to Nick about it, he was of the opinion not to bother. There aren't that many speaker protection boards that are fast enough to react, so I'm told. I haven't got anything in my 686, and I don't think I could fit anything in the case but I'd be interested to know what you recommend sq225917 |
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Bigman80
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Post by Bigman80 on May 7, 2021 5:45:48 GMT
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Post by alit on May 7, 2021 7:06:10 GMT
The points Nick made were that the more current an amp is capable of passing, the harder it is to break that current, and the bigger and more sonically questionable the relay needs to be to do this. You could parallel them up, but it just takes one to fail shut.
He pointed out that the speed of operation misses the point in his opinion, it would take at least a tenth of a second to tell a 20hz signal from DC so the detection has to be slow.
Oli, yes a bit different, earlier designs more simple. Less safeguards though..
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Bigman80
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Post by Bigman80 on May 7, 2021 7:40:48 GMT
The points Nick made were that the more current an amp is capable of passing, the harder it is to break that current, and the bigger and more sonically questionable the relay needs to be to do this. You could parallel them up, but it just takes one to fail shut. He pointed out that the speed of operation misses the point in his opinion, it would take at least a tenth of a second to tell a 20hz signal from DC so the detection has to be slow. Oli, yes a bit different, earlier designs more simple. Less safeguards though.. Ah, ok. So running through a fuse is better? I can stick a fuse in my box lol. That would fit 🤣 |
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Post by alit on May 7, 2021 7:52:44 GMT
Well it would be safer. The seller had this serviced a few years ago and the mains switch replaced. I can't see the tech removing the fuses from circuit , though if it was me I'd be a bit concerned that he didn't pick up on the fact that they had been disconnected.
I know the seller has owned this amp since the 90's, so it's quite possible he's been using it all this time like this. He's not technical by his own admission so had never messed with it.
It may or may not affect SQ and it wouldn't save your speakers, but the fuses would at least prevent the amp and/or speakers possibly going up in flames.
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Post by alit on May 7, 2021 7:55:25 GMT
BTW I ordered four of those Kasei caps to swap out.
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Bigman80
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Post by Bigman80 on May 7, 2021 7:57:29 GMT
Well it would be safer. The seller had this serviced a few years ago and the mains switch replaced. I can't see the tech removing the fuses from circuit , though if it was me I'd be a bit concerned that he didn't pick up on the fact that they had been disconnected. I know the seller has owned this amp since the 90's, so it's quite possible he's been using it all this time like this. He's not technical by his own admission so had never messed with it. It may or may not affect SQ and it wouldn't save your speakers, but the fuses would at least prevent the amp and/or speakers possibly going up in flames. Yeah, gotta be worth some investigation |
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Post by alit on May 7, 2021 8:01:19 GMT
Can't listen in my system as I stay with my girlfriend at the moment, but I do have my resistor box and my decent cans, so I'll have a good listen as is and then rewire it, see if I can hear a difference.
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Post by alit on May 7, 2021 8:05:16 GMT
Simon, did you put boards in yours?
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Post by alit on May 7, 2021 13:53:24 GMT
Fuses back in service, all is well and I can't hear any difference to the sound on my cans.  |
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Post by sq225917 on May 7, 2021 21:53:05 GMT
How fast does a fuse blow? It doesn't have to be a relay,a mosfet switch will do it, Tom's bridged guardian will protect a stereo amp from anything over 3v
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Bigman80
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Post by Bigman80 on May 7, 2021 22:07:14 GMT
How fast does a fuse blow? It doesn't have to be a relay,a mosfet switch will do it, Tom's bridged guardian will protect a stereo amp from anything over 3v Good bit of kit that, but damn it's pricey. Not a pricey as new speakers loike. |
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Post by antonio on May 8, 2021 1:04:24 GMT
I hope you put some exotic fuses in there Ali and not those costing tuppence.  |
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Post by alit on May 8, 2021 4:53:17 GMT
LOL, they look to be the original glass fuses. No foo.
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Post by alit on May 8, 2021 4:56:25 GMT
How fast does a fuse blow? It doesn't have to be a relay,a mosfet switch will do it, Tom's bridged guardian will protect a stereo amp from anything over 3v Hey don't shoot the messenger. :-) He also mentioned using Mosfets. |
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Post by sq225917 on May 8, 2021 14:35:03 GMT
Mosfets is the way forward.
Don't need protection in the mod86p, it uses stereo chips with over, under voltage, over current and over temp built in.
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Post by alit on May 8, 2021 20:01:55 GMT
I meant the Krell you did mate.
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Post by sq225917 on May 8, 2021 21:18:25 GMT
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Post by alit on May 9, 2021 9:09:08 GMT
Cheers.
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Post by Deleted on May 9, 2021 10:20:27 GMT
How fast does a fuse blow? It doesn't have to be a relay,a mosfet switch will do it, Tom's bridged guardian will protect a stereo amp from anything over 3v Good bit of kit that, but damn it's pricey. Not a pricey as new speakers loike. I fitted Gaurdians in my 686. I like my speakers, and at over €2k to replace them, it seemed sensible in the grand scheme of things. |
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Bigman80
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Post by Bigman80 on May 9, 2021 10:57:40 GMT
Good bit of kit that, but damn it's pricey. Not a pricey as new speakers loike. I fitted Gaurdians in my 686. I like my speakers, and at over €2k to replace them, it seemed sensible in the grand scheme of things. If I had room in my casework, they'd already be in. |
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