Popping amps (careful with those cones, Eugene!)

Hey folks!

I've been having some work done in my living room, so disconnected my speakers to store them. Hooked all back up a couple of days ago, and now my system is ususable... Whenever I move the input selector, or power any of the amps off there's a real bang through both speakers. I've had systems before which would pop now & again, but this is LOUD. I'm worried it could blow a speaker. This is a new problem. The system used to be dandy and nothing has changed except for my sticking wires back into the speaker cabs & tightening up the mitchells \

Any ideas what could be causing this or how it can be fixed? I'm thinking of capacitors discharging & similar, but don't know what I can do to track the problem down & then fix it.

System is...

2 x Kef Concerto 2 floorstanders
2 x Rotel RB 971 Mk II Power Amps
1 x Rotel RC 972 Pre Amp

The Kefs are bi-amped (the 971s are NOT monoblocked) one 971 drives l & r bass cones the other drives the tweets.

This is a serious request chaps, I hope someone can help as there are a few boxes there & most aren't available any more. I don't want to have to junk 3 amps & replace them if I can help it.

Many Thanks in Advance!
Chris

 

Have you checked you have wired everything back up the same?

OK. Just some thoughts.

1. Do you always make sure that the volume is right down when you power up?

2. Ensure you power up in this order SOURCE>PRE AMP> POWER AMP(s). Then power down in reverse. (Wait till you hear the relays in the amps click in before you turn anything up)

3. Try switching your power amps over. I presume it's the one driving the bass/mids that's making the noise. See if the problem pesists.

4. If your pre has a headphone socket listen through cans as you switch it on.

5. Triple check all wiring.

6. Is the sound audible in both speakers?

It sounds like dodgy power capacitors. Though I'd question 2 of them going down when you've only moved it a bit of a coincidence. I'd expect those to be fine.

 

Sounds like the storage could be an issue .....

I'm assumning this is independant of volume ?

with the pre disconnected vigerously work the selector swtich bag and forth....

if the units have got damp whilst in store warm them up for 20minutes [in a warm room] to drive off any condensation.

If the pre selector still pop [bangs] let us know.

 

Re-reading this it seems that the amps were left in situ and only the speakers were stored. Is that correct?

Did you disconnect/ reconnect with the units switched off? Check there isn't something like a hair of copper wire across the speaker terminals.

 

your right .......
still worth thinking about condensation ..if the heatings been off ?

Also spining the selectors not going to harm anything and might even clean the contacts

 

Thanks for the tips guys... Your assistance is much appreciated!
I'll try & answer each point in turn...

1) Yes. Volume is right down at power up & down
2) There's some joy here... I'll try & explain all the permutations...
If I power up as you suggested, all is well. If I power down in the reverse sequence, all is also well IF I wait about 10 seconds after switching off power amps, before switching off pre. If I switch off the pre with the power amps on (no volume) or I don't wait 10 seconds then BANG! If I move the source selector with everything powered up in the correct sequence, and no volume BANG!

3) Aha! I didn't switch the power amps over, but using only the amp which drives the tweeters then there are no bangs... ever... irrespective of volume, or flicking the input source, or power up/down sequence. So... it seems I'm left with one dodgy power amp?

4) Yes it does, but I don't have cans d'oh!

5) Haven't done this yet, but will do (see below).

6) Yes, both bass speakers pop. Music is fine in all 4 individual cones (if I play a CD after weeping for my speakers powering it all up lol).

Correct, only speakers were stored. amps et al were in situ in my living room, which is centrally heated & not damp. I did spin the source selector which seemed to have no effect.

I think next I need to re-cable everything to use a single poweramp, check for the problem, then switch over to the other one & check again (by the sounds of it)...

Assuming (as I now suspect) a duff poweramp, any ideas on what the problem with it is and how expensive it could be? I'm happy to just pay Rotel to fix it, but obviously not if the cost is gonna run into hundreds, and the other one is gonna go the same way at some point... (or if there's better kit out there for similar cost etc etc.)

I realise that last one's difficult to answer definitively from just observations on a forum thread, but I'd appreciate thoughts/speculation etc. as you guys obviously know your stuff.

Lastly, any experiences (good or bad) of using Rotel's service depts? I'm assuming they have one lol.

 

Forgot to say when signing off...

Thanks again guys... much appreciated...

 

Lastly, any experiences (good or bad) of using Rotel's service depts? I'm assuming they have one lol.

Good. Replaced a belt for my Rotel cd player free of charge. Jim.