SpeakerTalk Forum Index SpeakerTalk
This forum has been set up to facilitate discussion of 1970s KEF speakers and drive units. The owner of the Forum has no connection with KEF Audio.
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

Just picked up pair of 105.2's Have S-Stop ?

 
Post new topic   Reply to topic    SpeakerTalk Forum Index -> KEF Speakers from the 1970s
View previous topic :: View next topic  
Author Message
pcolafins13
Junior Contributor 10+


Joined: 16 Apr 2017
Posts: 10

PostPosted: Sun Apr 16, 2017 9:48 pm    Post subject: Just picked up pair of 105.2's Have S-Stop ? Reply with quote

Hi everyone. I'm new to the Forum. I just purchased my first pair of vintage Kef's, but I've been a KEF fan for a good while with my main speakers being the more Modern XQ-40's which I love! I hooked up my recently acquired 105'2's yesterday, and MAN! These things deserve all of the praise they have received. They sound amazing! Having said that, I am experiencing one issue. I'm running them with a pair of Aragon palladium ii Mono blocks which are rated at 400 watts each. I realize that the 105'2's are rated at 200 watts max. The issue I'm having is that one of the speakers shuts off and on when i crank them up , and I'm assuming it's the S-Stop protection activating. The Red Peak indicator light is not coming on, and the other speaker plays fine. I am not clipping the amp, and the volume level although loud isn't Excessively loud and shouldn't be triggering the protection. Any suggestions on what I can do to eliminate this problem? I'm not a tech savvy kind of guy, but I do have some nearby friends that are. I'm thinking possibly bypass this protect circuit?? Thanks for any advice.
Back to top
View user's profile Send private message
audiolabtower
VIP Contributor 500+


Joined: 06 Jan 2009
Posts: 544

PostPosted: Sun Apr 16, 2017 10:31 pm    Post subject: Reply with quote

I've seen reviews where 1000W peak have been tolerated on wide dynamic range material for short periods of time so the speakers are by no means limited to 200W, there are too many variables in heating up the voice coils or driving beyond travel limits to be specific about music material wattage as opposed to constant sine waves.

I have Mk1s which had thermally matched fuses instead of the SStop and have used them for 30 years with the protection, but am not a heavy metal headbanger (or do high speed tape reeling anymore), but do play at realistic concert hall/opera house impact in a large room.

Not being familiar with the SStop internal circuitry (if anyone actually has any complete diagrams) I would guess one of your circuits has drifted. You could drive both in mono and see if the leds come on at the same time might give a clue.
Back to top
View user's profile Send private message
pcolafins13
Junior Contributor 10+


Joined: 16 Apr 2017
Posts: 10

PostPosted: Mon Apr 17, 2017 1:02 am    Post subject: Reply with quote

Thanks for the reply. The LED's do not come on at all except when doing the initial setup. I just meant they are rated for 200 watts. I know generally clean power won't hurt speakers and these Aragons are top notch amps. I'm hoping someone may chime in with a suggestion. Maybe bypass the protect circuit or have the crossovers rebulit. I'be read something about a kit that can be ordered with new capacitors etc from Falcon Acousitcs. Anyone have any experiemce with that? if so, did it improve the sound? Thanks
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


Joined: 18 Nov 2005
Posts: 959
Location: Green Hut, Tovil

PostPosted: Mon Apr 17, 2017 8:47 pm    Post subject: Reply with quote

I know it would be a lot of work, but you need to swap protection boards to see if the fault travels across. With one system working properly and the other cutting out prematurely, the best way to isolate the problem is by swapping parts across and back.

I do have some s-stop spares.
Back to top
View user's profile Send private message
audiolabtower
VIP Contributor 500+


Joined: 06 Jan 2009
Posts: 544

PostPosted: Mon Apr 17, 2017 9:44 pm    Post subject: Reply with quote

pcolafins13 wrote:
The LED's do not come on at all except when doing the initial setup.

They should blink on at the 50 and 60 peak positions if you play loud?
Back to top
View user's profile Send private message
pcolafins13
Junior Contributor 10+


Joined: 16 Apr 2017
Posts: 10

PostPosted: Mon Apr 17, 2017 10:32 pm    Post subject: Reply with quote

I did try turning the knob to the lower wattage setting last night, and the red lights never came on. As for swapping the protection boards, is that pretty easy to do once i get in there? I'm a dummy when it comes to that kind of stuff, but if its a simple unplug and swap out then of course i could do that.
Back to top
View user's profile Send private message
pcolafins13
Junior Contributor 10+


Joined: 16 Apr 2017
Posts: 10

PostPosted: Tue Apr 18, 2017 3:36 am    Post subject: Reply with quote

speakerguru wrote:
I know it would be a lot of work, but you need to swap protection boards to see if the fault travels across. With one system working properly and the other cutting out prematurely, the best way to isolate the problem is by swapping parts across and back.

I do have some s-stop spares.

I have a very knowledgeable friend whom i plan to show the crossovers to once I pull them. Are the S-Stops something that can be "restored/repaired" or would replacements be in order from someone like you? thanks
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


Joined: 18 Nov 2005
Posts: 959
Location: Green Hut, Tovil

PostPosted: Tue Apr 18, 2017 10:08 am    Post subject: Reply with quote

pcolafins13 wrote:

I have a very knowledgeable friend whom i plan to show the crossovers to once I pull them. Are the S-Stops something that can be "restored/repaired" or would replacements be in order from someone like you? thanks

The passive power supply part of the s-stop board is made up of regular discrete wired components, four of which are electrolytic capacitors. These are the most likely components to have dried up and failed after all these years. The active psu high voltage transistors, rms detector, relay driver and other stuff is in four thick film modules. One is a resistor array. the other three were custom designed, only made for and supplied to KEF Electronics.
Back to top
View user's profile Send private message
pcolafins13
Junior Contributor 10+


Joined: 16 Apr 2017
Posts: 10

PostPosted: Thu Apr 20, 2017 3:03 am    Post subject: Reply with quote

I have read that there are two versions of the 105.2's? I can't seem to find any info to know exactly how to tell. My serial number is 6154. I read it depends on your serial number?? Thanks again
[/img]
Back to top
View user's profile Send private message
speakerguru
VIP Contributor 750+


Joined: 18 Nov 2005
Posts: 959
Location: Green Hut, Tovil

PostPosted: Thu Apr 20, 2017 8:32 am    Post subject: Reply with quote

pcolafins13 wrote:
I have read that there are two versions of the 105.2's? I can't seem to find any info to know exactly how to tell.

As far as I can remember, no, there was only one version of 105|2.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SpeakerTalk Forum Index -> KEF Speakers from the 1970s All times are GMT + 1 Hour
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group