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Reference 101 S Stop circuitry fault

 
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lamda69
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PostPosted: Wed May 03, 2017 9:59 pm    Post subject: Reference 101 S Stop circuitry fault Reply with quote

Hi Folks - I recently purchased a pair of R101s on that auction site that were described as "in good working condition". Actually the seller didn't know anything about them. It turns out that one B110 voice coil was scraping (sounds like mistuned FM station). I have a new pair ordered from Falcon.
Both S Stop circuits are behaving badly. When I turn on the amplifier (60 watt tubed) there is no sound. I have to get the volume knob up to 10 o'clock before both kick in at a volume higher than I would normally listen to (pardon me MR. Churchill). Does anyone have any idea what is going on and how to repair the circuit. Meanwhile I have found the place on the circuit board to jumper and bypass the S Stop if all else fails. Thanks in advance.
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audiolabtower
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PostPosted: Thu May 04, 2017 12:39 pm    Post subject: Reply with quote

Unfortunately the Falcon B110 is a SP1003 replacement, not the SP1057 which was used in the 101. The 1057 had twice as much power handling and a smoother response. In the event of no spares the only route left will be to disconnect the sstop input and relay.
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speakerguru
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PostPosted: Thu May 04, 2017 2:35 pm    Post subject: Re: Reference 101 S Stop circuitry fault Reply with quote

lamda69 wrote:
Both S Stop circuits are behaving badly. When I turn on the amplifier (60 watt tubed) there is no sound. I have to get the volume knob up to 10 o'clock before both kick in at a volume higher than I would normally listen to (pardon me MR. Churchill). Does anyone have any idea what is going on and how to repair the circuit. Meanwhile I have found the place on the circuit board to jumper and bypass the S Stop if all else fails. Thanks in advance.


The S-Stop relay is normally on when not energised by a triggered protection circuit. If it does not let through the signal at low volume levels then it is most likely dirty contacts causing the problem.
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lamda69
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PostPosted: Thu May 04, 2017 3:18 pm    Post subject: Thanks Guys Reply with quote

I can not believe I didn't notice that the Falcon version was the wrong one. Nice catch. I emailed the and cancelled that portion of the order as the web site said the order was still processing. I'll check for bad contacts on the S Stop, otherwise I'll just bypass it and fuse the tweeter.

I am fortunate that an appropriate B110 with matching DCR just popped up on ebay. Thanks again guys!
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speakerguru
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PostPosted: Fri May 05, 2017 10:43 am    Post subject: Reply with quote

Try to get new relays. Abrasive cleaning of relay contacts usually destroys the rare metal coatings and they'll go again very soon.

Only one German make of 400mA T (antisurge) fuse had a time constant that was a good match for Kef tweeters. I have forgotten the brand name, sorry.


Last edited by speakerguru on Mon May 08, 2017 8:38 am; edited 1 time in total
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lamda69
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PostPosted: Sun May 07, 2017 8:28 pm    Post subject: Reply with quote

Got my replacement B110 and they sound great. I have the SA Stop circuitry bypassed. I really do not understand it. Are the relays the rather inductor-looking items? Is there a way I can test to see if they arew still good. I have not found a schematic of the S Stop circuitry and have no idea of what is in that sealed unit with the KEF logo on it. What about the two transistoe-looking devices. Thanks for all your help guys. I'm totally ok with the S Stop bypassed.
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audiolabtower
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PostPosted: Mon May 08, 2017 3:33 pm    Post subject: Reply with quote

I'm not sure if SpeakerGuru actually designed these speakers, so he should know Smile but from memory it has 2 large inductors and 1 small inductor in the crossover which are wound on iron dust cores, so the last thing on the board that looks like a relay should be one (I think the module only has the input sense and relay drive circuit in it)?
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lamda69
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PostPosted: Sat May 27, 2017 4:53 am    Post subject: Reply with quote

I have tested my new 101s with a sound level meter and used the accepted compensation for the readings. If we use 1KHz as the reference the output below that is running roughly -2db while the output above the crossover point is running about +2db except above 10-12KHz where it runs hotter. If I wanted to cut the tweeter level by about 2db, what would be the cleanest way to do it? In fact they sound really good to me but I'm 78 and can barely hear a 10KHz signal. 8KHz seems to be about it for me. I'm afraid I might sear friends ears when they visit. Would increasing the 2R2 to 4R4 do it or would that muck up something else. Thanks for your help.
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speakerguru
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PostPosted: Sat May 27, 2017 8:46 am    Post subject: Reply with quote

Did you test outdoors or do you have access to an anechoic chamber? Otherwise you will be measuring the effect of standing waves and room reflections. These do not correlate well with subjective frequency response/balance.
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lamda69
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PostPosted: Sat May 27, 2017 8:57 am    Post subject: Reply with quote

I tested in my living room. I had not considered room reflections. Would they kick in as low as 3KHz? The increase in output does not appear until just above the crossover point. I clearly see floor and ceiling bounce.
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lamda69
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PostPosted: Sat May 27, 2017 5:18 pm    Post subject: Reply with quote

Now that I've had my coffee... Laughing . I used a Pierre Verany test cd with warble tones to prevent standing waves. I have used his multiple times before and not gotten this kind of response. Anyway, is there any easy way to cut the tweeters response by about 2db without resorting to a L-pad?
Thanks
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speakerguru
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PostPosted: Mon May 29, 2017 8:14 am    Post subject: Reply with quote

lamda69 wrote:
....Anyway, is there any easy way to cut the tweeters response by about 2db without resorting to a L-pad?
Thanks

Not really. A resistive L pad will change the load impedance as seen by the XO components, so that will change the frequency response. The only accurate way is to use a simulator having first obtained a measurement of the tweeter impedance.
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