nik
New Member
Posts: 4
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Post by nik on Dec 29, 2020 9:00:39 GMT -5
Hi guys! I hope you all and your families are well and staying safe. First of all Merry Christmas and a happy new year!
I'm new to this forum. I found it incredibly interesting. I'm an handy guy and I like to fix all kinds of stuff. I have an Onkyo TX-RZ800 that is making an loud popping noise coming only from center speaker when something changes to the audio signal. For example, when switching the sources, when changing the listening mode (for example from DTS to stereo, or another audio format), even when watching YouTube and going to next track or adverts showing up. Either way everything is working perfect, all channels working fine, even the center one, and the sound is fantastic. If I'm watching an movie and the audio signal is not changing, remaining DTS for example, no popping noise.... If while watching an DVD I go back to the menu, then only the center channel pops. If I deactivate the center chanel from the receiver menu, all fine, no popping noise from the other channels at all... So far I downloaded the service manual I dismantle it and I followed the center chanel along all the boards and redone most of the soldered joints. I found few bad connections on some boards, mainly in final stage of the amplifiers, but nothing changed after all... Still making the annoying popping noise. I thought is an bad soldered joint somewhere, but seems is something more deep.
Please, any idea where I should look? What board could cause this annoying popping noise?
Thank you in advance!
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Post by tibimakai on Dec 29, 2020 16:27:39 GMT -5
You are not talking about aa relay switching? That is normal.
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nik
New Member
Posts: 4
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Post by nik on Dec 30, 2020 11:42:24 GMT -5
Thank you for your reply!
No unfortunately. Is not an mechanical noise. I know about the relays clicking noises... This noise is on top of that and is coming from the center speaker, not from the unit himself. If I take of the center speaker dust cover I can see the speaker cones pushed forward when it pops up. And that is happening ONLY for the center channel.
It's that classic popping noise found in classic amplifiers, with no delay circuits for the preamplifier, when you turning it on, or when you changing the source.
I suppose that this newer receivers have some muting / delay circuits to get rid of that normal popping noise found in old amps. It is like the delay / muting circuit is not working properly for the center channel.
Please have a look at this link.
I put this link only as an example... Is not my amp in the video, but behave the same. Mine is popping louder and is really annoying when you listen at lower volumes.
I have replaced the cable and the center channel speaker, then disconnecting everything from the amp, using only the the Internet radio as a sound source and the noise is still there, I even dismantle it and redone most of the soldered joints across most of the boards... (found some cracks in some soldered connections). Didn't helped. Any advice is more than welcome.
Thank you in advance!
Kind regards
Nik
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Post by tjmotter on Jan 1, 2021 14:02:13 GMT -5
I would recommend that you check the "mute" transistors for the Center channel. I am not saying this is likely but it is a good place to start. I once repaired an NR616 that pushed a loud "pop" out of the subwoofer at startup and found that these transistors had blown. You should look for Q4612 and Q4602 (RTAN430C-T112-1 but you can also use RN1441's which are listed as alternative parts in other designs). They should be located on the underside of the bottom most board surrounded by the Mute transistors for all the other channels. These transistors have an integrated resistor so they are a little odd to test but if you compare resistance measurements between Collector/Base/Emitter to other transistors in that area, (in both +/- directions) you should be able to determine if these two are bad.
It is possible that much like my NR616 fix, Onkyo was aware that a spurious signal would be created during a transition and that they intentionally mute the channel during that transition. If either (or both) of these transistors have failed, this could explain it.
While you are in there I would consider changing C4602 (47uF 50V) which could be another source of the pop.
HTH
Todd
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nik
New Member
Posts: 4
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Post by nik on Jan 7, 2021 8:35:33 GMT -5
Thank you Todd for your advice. Those transistors, measured in the circuit, indeed they're odd. I measured them and I noticed a tiny difference between those two transistors and the others from the other channels. Anyway I will replace them. I struggled to find them in UK. Seems they are discontinued everywhere. I found RN1441ATE85LF in China. I don't know when they'll arrive. I'm also afraid to not be counterfeit. I also changed C4602.
If anyone knows another compatible ones or have some other ideas is more than welcome.
Thank you all for your support!
Kind regards
Nik
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Post by tjmotter on Jan 7, 2021 13:00:43 GMT -5
Thank you Todd for your advice. Those transistors, measured in the circuit, indeed they're odd. I measured them and I noticed a tiny difference between those two transistors and the others from the other channels. Anyway I will replace them. I struggled to find them in UK. Seems they are discontinued everywhere. I found RN1441ATE85LF in China. I don't know when they'll arrive. I'm also afraid to not be counterfeit. I also changed C4602. If anyone knows another compatible ones or have some other ideas is more than welcome. Thank you all for your support! Kind regards Nik I know that the RN1442 is also obsolete but it appears to still be available in the US from companies like Digikey. It is from the same family and has the same pinout but seems to differ in the HFE rating which shouldn't matter but I should note that the internal resistor is slightly bigger (RN1441: 3.9K ohms RN1442: 7K ohm) since this circuit does not require gain, simply "switch" operation, I suspect it "should" work.
HTH Todd
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nik
New Member
Posts: 4
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Post by nik on Jan 16, 2021 18:33:25 GMT -5
Hi guys!
Update :
The transistors from China just arrived. I've ordered RN1441ATE85LF. Which seems are the same thing if you look at the data sheet.
I couldn't wait and replaced Q4612 and Q4602. I rebuild the amp and tested. And.... YUPPIE! PROBLEM SORTED - No popping noise at all.
Thank you all for help!
Thank you so much Todd! Your advice was priceless.
Best wishes
Nik
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