Onkyo A-9155 weak right channel

[LM3886TF]

Hello to everyone!

I have Onkyo A-9155 amp with 2 speakers. Here is the problem: When i turn it on, right channel is 50% weaker than left one. Then i turn volume a bit up and both channels are running fine, even if i turn pot meter back on low volume. After some time, let's say, 30 mins, right channel again starts to be weaker until volume is turned up again.
It happens on all inputs (CD, Tuner...)

Service manual / schematic can be found here: http://tinyurl.com/z5smyxt

I haven't opened it yet. Plan was attaching signal generator from PC (sinus 1 khz) on input and tracing (comparing with left channel) signal with scope.

Question is, do you have any experience with such problems and idea what to check first?

Also, this schematic is "broken" into two pages...anybody has anything better than link provided?

Thanks!!

[keeney123]

Re: Onkyo A-9155 weak right channel

Sounds a bad connection or a bad potentiometer. Could even be the output relay contacts. Does it do it on the headphones?

[LM3886TF]

Re: Onkyo A-9155 weak right channel

@Kenney123 thanks for your tips.

I've finally disassembled amp and figured out that problem is in the output relay (RL592). It's right one on the picture. When i press it with finger or poke it, the "effect" of weaking and "coming" of right channel is present.

Also, both relays are taped with kapton tape

[madan1]

Re: Onkyo A-9155 weak right channel

Huh.. someone had "repaired" them in the past. Can you take a photo of the bottom side of the pcb?
Usually that relays are not serviceable, but ( as probably done before ) you can open and clean them. If there is something broken inside you have no other option, but to buy a new one.
From what you've said, I guess that resoldering the relays will fix the issue ( at least for now ).

[keeney123]

Re: Onkyo A-9155 weak right channel

@Kenney123 thanks for your tips.

I've finally disassembled amp and figured out that problem is in the output relay (RL592). It's right one on the picture. When i press it with finger or poke it, the "effect" of weaking and "coming" of right channel is present.

Also, both relays are taped with kapton tape

So someone opened the relay cover and lightly sanded the contact points. This is good for a short period of time. The kapton tape was to seal them up again. I would replace both relays with new ones. Usually if the contacts are worn out on one the other is not to far behind. What happens is the contacts get pitted and one can sand the pits out for a temporary fix. They are sealed to protect them from oxidation. I am sure oxidation still occurs but more slowly. If they pull a vacuum on them then I would say they would even last longer.

[LM3886TF]

Re: Onkyo A-9155 weak right channel

Thnx for the info guys.

I haven't removed PCB, as soon as i saw what is the problem i ordered new relay. I also think that resoldering will resolve problem, but to be on the safe side i ordered new relay. Since removing PCB seems to be a bit complicated (and i'm short with time and space these days) i wanted to have spare relay ready before i continue.

So someone opened the relay cover and lightly sanded the contact points.

Would you be shocked as me when i say that i bought this amp as brand new from Onkyo retailer here in Croatia? Sealed, packed in the box. This is its first service or cover removal at all. I wonder what will come up from bottom side of pcb.

[keeney123]

Re: Onkyo A-9155 weak right channel

Thnx for the info guys.

I haven't removed PCB, as soon as i saw what is the problem i ordered new relay. I also think that resoldering will resolve problem, but to be on the safe side i ordered new relay. Since removing PCB seems to be a bit complicated (and i'm short with time and space these days) i wanted to have spare relay ready before i continue.



Would you be shocked as me when i say that i bought this amp as brand new from Onkyo retailer here in Croatia? Sealed, packed in the box. This is its first service or cover removal at all. I wonder what will come up from bottom side of pcb.

So no I would not be shocked. There could be several reason for this. 1. who ever manufactured the board for Onkyo has bad repair practices on new boards. 2. The retailer in Croatia repairs the units out in the field instead of sending them back to the parent company. So if a customer has a bad unit he gives them a "new" unit and repairs the bad one. Then if another customer has a bad unit he gives them the repaired unit and calls it "new". 3. The other thing is a used unit can be repackaged and then sold as a new unit.

So if the unit is indeed new then the manufacturer ran into a bunch of bad relays and for whatever reason they found it easier to open the relay up instead of putting in another relay.

Either way you should contact the parent company and tell them what you have found. Of course opening the unit nullifies the warranty.

[LM3886TF]

Re: Onkyo A-9155 weak right channel

Warranty won't apply anyway...it's 5 years old unit.

Ill post results and pics when new relay comes.

thanks!!

[momaka]

Re: Onkyo A-9155 weak right channel

Interesting find with the relays. Let us know how the new relays work.

I have a Denon AVR-3200 that has a somewhat similar problem - it won't play sound from the speakers until I turn the volume up to a high level or playing with Stereo/5-Ch output (which has the effect of cycling the relays ON and OFF). Once the speakers start playing, I can turn the volume up and down as much as I like and they won't go off again. So maybe mine has bad relays too, which is why I am curious how the new relays will work in your unit.

[kc8adu]

Re: Onkyo A-9155 weak right channel

bad solder joints or the contacts are fouled.
had a relay in the pa section of a kenwood ts-2000 foul like that.
bought it cheap as p o thought finals died.
gotta love deals like that.relay switches drive from hf/6 to vhf section.

[madan1]

Re: Onkyo A-9155 weak right channel

and look what I found in an ONKYO unit with no signs of any repairs

All 5 "high" ala2f24 relayes have kapton on their lower part.

[momaka]

Re: Onkyo A-9155 weak right channel

So maybe this tape was factory-fitted then?