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KEF PSW-2500 Subwoofer
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kefpsw3000
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PostPosted: Sun Mar 18, 2007 2:31 am    Post subject: Reply with quote

My PSW-3000 started to do the same thing. Works for a few seconds/minutes then it makes a sudden sound and it quits.

I took the sub apart and I played around with the power supply connectors. In the end, it looked like a relay is cutting the amp, basically what others have descibed in here. I can get the sub to work for a few minutes if I unplug the small red/blue/black power connector to the amp circuit board. The person who posted before me, the other guest, where is the capacitor that you replaced? Could you post a picture or two on where this capacitor is located? I really like the PSW-3000 and I would be awesome if I could bring it back to life.

Any help?

G.
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Brianthe spark



Joined: 18 Mar 2007
Posts: 1

PostPosted: Sun Mar 18, 2007 4:40 pm    Post subject: Reply with quote

I have a kef 2000 sub, all op transistors went short along with the -15 regulator.
The relay had got hot and all contacts had shorted together conecting the op to gnd. Had to take relay apart to find this out.
My problem now is the high wattage 270 ohm resistors by the large caps have done and still run very hot. The regs also run hot. Any ideas. A schematic of any kef sub would really help.

Thanks
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guy
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PostPosted: Mon Sep 08, 2008 5:58 pm    Post subject: ticking relay Reply with quote

hi,
i've noticed that this thread is old but....
i have a problem with my psw2500,it won't turn on.
there is a loud ticking noise from the relay,i replaced it and
its just the same.
anyone?????????pls?????
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Scur
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PostPosted: Thu Nov 13, 2008 5:37 pm    Post subject: Reply with quote

I have the same problem the relay ticking and the sound is crap.
Some one have this problem?
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halfpint55
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PostPosted: Tue Jun 02, 2009 3:58 pm    Post subject: Reply with quote

I have spent ages trying to sort mine, everything that could have gone wrong with it has. The resistors that people are saying are getting hot are suppose to. They are stepping the 55v down to about 20v for the 15v regulators, just a cheep nasty potential divider circuit. The bridge rectifier first fried on mine, then the power transistors went short circuit. Replaced all damaged parts but i have a feeling the problem may have run back to the signal board. I have never seen a power transistor fail in such a spectacular way. Even the transistor legs have melted!!! I have reversed engineered a schematic of the power/amp board and have realised that it is a not particularly well designed product. I have given up trying to mend it as every time I had got it working again it would just destroy itself again within weeks with a different or similar fault to all those of which have been mentioned on here. I am now in the process of designing some electronics that work for it and putting then in the existing enclosure. In conclusion dont bye a kef!
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vtech



Joined: 08 May 2006
Posts: 1264
Location: USA

PostPosted: Tue Jun 02, 2009 10:32 pm    Post subject: Reply with quote

Goes to show you that despite what you may read or hear about a certain product, it is more likely not what is cracked up to be, especially in quality design.
Using a power resistor for DC step down in an audio gear? .. that is awful!
While I liked their speakers, I never cared much for their subs(& many other brands for that matter). While they look good & massive physically, the electronics inside is usually pretty dismal to say the least.
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johnb1111
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PostPosted: Wed Apr 28, 2010 2:27 am    Post subject: KEF PSW 2500 relay buzz and audio outout buzz Reply with quote

Have just repaired a similar problem with a KEF 2500 - relay was chattering at 50 Hz rate, buzz in speaker output.

Problem was caused by overheated / dried out Electrolytic filter cap (C52 - 47uF 63V) on the relay coil supply feed.

The overheating is caused by adjacent power supply dropping resistors which run very hot due poor design of power supply.

A service manual for a similar model is available at eservice manuals, refer to power supply section:-
Note this is not the same model, but it is very similar.

See manual at eserviceinfo.com/downloadsm/35375/kef_psw2000.html

To replace,

1) remove chassis from speaker cabinet (8 screws), disconnect red/black speaker wires from main PCB spade connectors.

2) Remove 4 screws attaching main pcb heatsink assembly from face panel - lift assembly from faceplate (a bit messy , much heartsink compound between mounting faces)

3) unplug the AC 3 pin connections adjacent to the large capacitors and the 3pin connector on end of pcb (near C52), then roll assembly over the top of the audio sub-board to access underside of pcb.

4) solder connections to C52 is accessible at edge of board without further dis-assembly.

Take extreme care replacing C52, as the circuit board is of poor quality, (usual domestic electronics quality) being single sided copper without plated through holes.

The board is already heat damaged by heat buildup from power supply resistors, so the track will most likely lift and crack when disturbed- to counter this problem link the +ve capacitor pigtail to an adjacent solder pad on the same track - and physicaly lock the body of the 47u capacitor to the adjacent large capacitor with glue or cable tie.

Assembly is reverse of above, take care to preserve/ensure minimum disturbance of heatsink compound.
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Rickoray
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PostPosted: Sat Aug 14, 2010 11:55 am    Post subject: Reply with quote

Thanks for this tip!!!

My PSW2500 Subwoofer did the same problem too, the relay pulsated at high rate, I changed the C52 Cap which was dead, and my sub is OK now!


Very Happy

Thanks a lot!!!
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Bas Horneman



Joined: 22 Jan 2011
Posts: 1

PostPosted: Sat Jan 22, 2011 2:25 pm    Post subject: Thanks for the tip guys. Reply with quote

Replaced it with a 105 degrees version. And voila it worked like a charm again. I also left the leads a little longer so that I could keep it further away from the hot resistors.
See pic.
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kcsolomon
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PostPosted: Thu Jul 28, 2011 4:45 pm    Post subject: Transformer Voltage Reply with quote

My Kef 2150's transformer is outputting 38-39vac Yellow to Black. I don't think that is right. Should it be 15vac or 50vac?
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