Onkyo TX-2500 - 'wobbling sound'

[RobbertHesen]

Hello everyone,

I've got an Onkyo TX-2500 receiver back home with Jamo 28 speakers.

Everything worked perfect, however since a couple of weeks the speakers give a 'wobbling' sound.
I realize, 'wobbling' is a vague term so I'll try to explain it in detail.

After I turn on the receiver, both speakers start giving a (fastly) pumping bass. Even when there is no music on.
It's more like a speedcore bass. After turning the bass to zero, the 'wobbling' sounds stops as well.
I tried a different set of speakers as well, but with both speaker sets this issue occured.

So, I guess the problem is not with the speakers but with the Onkyo receiver.

Anyone, got an idea how to solve this problem? And can I fix it myself?

I really appreciate any help you can provide!

Cheers,
Robbert

 

[slimecity]

Its low frequency oscillation.

Does it happen on both channels?

How long after startup does this happen usually?

Does this happen on one input, or on all inputs? Does it only happen on phono?

I cant find a good enuf pic of the back of this unit - but do you have "pre out" and "power in" RCA sockets at the back of the unit?

 

[Ghonk]

I had a 2500,no in/out connects.

 

[RobbertHesen]

Attached you'll find the current set-up of my receiver.

It happens on both channel A and B.
At first it happend after some time, however now it happens immediately after turning on the power.

Anyway, my turntable is connected to the phono of course.
And my tulip-aux cable is connected to tap 1 (input).

Thanks for the fast reply!

 

[jozeppy26]

You’re not using a speaker cable with a very high capacitance or something are you?

 

[Mico]

[QUOTE Anyway, my turntable is connected to the phono of course.
And my tulip-aux cable is connected to tap 1 (input).Thanks for the fast reply![/QUOTE]

And I do not see the ground wire for the turntable? Not sure it would be causing the subsonic frequency, just my 2c....

 

[jozeppy26]

Maybe move the speaker wire away from the power cord?

When it’s oscillating try moving the power cord and see if it changes it at all? Maybe it’s a shielding problem with the amps power source?

 

[crazy-in-az]

I would suggest moving the turntable to a different surface and getting it off the top of the receiver. Make sure the speakers and TT are not on the same surface.

 

[slimecity]

Im still not clear if you are only having this problem on the phono/turntable input, or on other inputs too?

 

[RobbertHesen]

Im still not clear if you are only having this problem on the phono/turntable input, or on other inputs too?

On both inputs, the problem even occurs without having any input connected.
Anyhow, I'd tried all above stated suggestions but it doesn't change anything...

I found something online about: "Motorboating"
This is very low frequency instability at around vibrato frequencies, 1 to 10Hz. In older amps this is almost always due to large value electrolytic capacitors 'drying out' or basically losing capacitance with age. Sometimes these can be 're-formed' but replacement is often a better option.

This seems in line with my problem (correct me if I'm wrong)
Anyone familiar with this problem? And can it be easily fixed or should I bring it to a shop for repairment?

Cheers

 

[Mico]

This makes some sense, but filter caps usually give low frequency hum yours might be beyond that stage,. Does "motorboating" goes away after a while or stays there all the time? it is very easy to change big filter caps on Tx2500, Mk1 or Mk2.
If you opt for DIY replacement there is lot of help and guidance you can get here, pro servicing gives you free hands but costs much more.