SpeakerTalk

[JeffS]

Hello all - I'm the original owner of a pair of 103/3's and was in the midst of enjoying some of the old magic from these speakers after having the tweeter ferrofluid and the deteriorated woofer annulus replaced. Unfortunately my Kube developed a problem shortly afterwards, and sadly I may be in the market for new speakers if I can't resolve.

The issue is that a random, static-y noise is coming from both speakers. It is not always present, and varies in intensity. If I take the Kube out of the loop it goes away, so clearly it is the culprit. The same thing happened to my original Kube about 10 years ago but I was able to find a replacement. I don't think that will be possible now, and even if I do find a new one it will probably be nearing similar failure due to age.

I'm not really knowledgeable about electronics, but I can do basic soldering, so if Speakerguru or someone can help me identify a likely culprit for the problem and the suitable replacement part, I will take a shot at fixing. If this is one of those problems where it could be multiple causes and needs troubleshooting, I would look for any recommendations for a repair shop (I'm in the states).

Thanks for any help!
Jeff

[speakerguru]

After all these years the switches can cause trouble. Operate them several times to see if that cleans up the contacts. My own 102 Kube sometimes loses one channel if I don't remember to work the switches every now and then.
If it's not that, then the only way I know to isolate an op-amp that's gone noisy, is to heat up each one in turn by applying a soldering iron close to the top and see if the noise gets worse. You could also use a freezer spray on each component in turn and see if the noise reduces. Good luck.

[JeffS]

Thanks Speakerguru. Operating the Extend, Tape, and Contour control doesn't really seem to make any difference.

Does the fact that both channels are affected offer any clues? Does a single op amp affect both channels or only one? Looks like there are 6 on the circuit board (TL072CP).

I have the luxury of having 2 Kubes - my old one that went bad and the current one I am using.The old one has the same condition but much worse. So I could play around with the old one and not risk my current setup. Is there a way to use Deoxit spray to clean the switches just in case that is the problem? They all seem to be pretty well sealed.

[speakerguru]

They are all dual opamps but I can't remember if they were split channel-wise. Don't forget the voltage regulators when you do the soldering iron/freezer spray testing.
Re switch cleaner, can you not get to the sliding part from the rear of the switch?

[JeffS]

I think I could probably get the cleaner in there some way, but I decided to give up on the idea of attempting any repairs myself. There is a local vintage stereo repair shop, and I was able to talk to the owner today and it sounded like he was familiar with the Kube. So I'm going to see if he can fix.

I'll post back with the results in case anyone is in my neck of the woods (Albany, NY) and is curious how the repair shop performs. Thanks again for the help!

[JeffS]

So to conclude the story I took the Kube to the local repair shop, explained the problem, and they proceeded to just clean the contacts and switches and proclaim it fixed the next day. I was doubtful but took it home hoping for the best.

Sure enough I connected the Kube back up and the static was there as before. Arghh!!! As I fumed over having wasted my time and money and still no closer to a solution, I decided I would verify once again that the Kube was the culprit and not some other component like the amp. So I remade the connections and pulled the Kube out of its place in the rack, and....no static. Tried the same setup with my 2nd problem Kube, and again...no static.

Turns out using different audio interconnects, and routing them away from existing power cables and other interconnects has apparently solved the problem. So it appears to be an interference problem, perhaps related to shielding in the interconnect. I might be tempted to blame the interconnects alone, but these were the same ones that were used on the original Kube (that was good and then went bad, and then on the new Kube, which also started out good and then went bad... apparently). Why this issue was non-existent for years, then developed suddenly - on 2 different Kubes and on both channels no less, is a mystery. But the static is gone now - on both Kubes, and I'm very happy about that.

[speakerguru]

Glad you found a solution. In defence of the repair shop, I guess they must have a much cleaner environment re EMC than your home.

I must also admit that there were no particular EMC measures taken in the design of the KUBEs, which all pre-date the 1997 EU directives on EMC (= your FCC EMC regulations). I'll post a sticky re EMC asap.

Having said that, I've never had any problems with my 102 KUBE despite living 3 miles away and in line of sight of a 1MW FM transmitter!

[JeffS]

Yes I can't really fault the repair shop too much, it was really my fault for not troubleshooting the problem enough up front. They probably couldn't reproduce the issue and just figured they would clean the contacts - it was cheap enough at any rate.

I'm using the 103/3's as part of a 7.1 Home Theater rig that also gets used for 2 channel, so there are quite a few cables in the rack by the Kube for all that gear. I had replaced one audio component a little while back and the problem started shortly afterwards. Guess the cables got moved during that process and introduced the interference issue.

Still no noise after about 2+ weeks , so guess it is officially fixed. Hopefully this thread may help someone troubleshoot similar issues going forward. And thanks again for your feedback SG!