Onkyo TX-NR636 shuts off on source/track change - Page 1
Forum section: electronics / repair

author: vef445
author_rank: Contributor
timestamp: August 30, 2018, 09:27:43 am
content: Good morningI'm having a problem with my receiver Onkyo TX-NR636.For those who know the usual "click" noise from the relays when changing a music track, changing input or simply pause/play a track on these Onkyo receivers, this is precisely the moment when my receiver goes to protected mode and shuts off. The diag function on restart tells a voltage error. Also note that when this happens I can hear a fairly loud cracking sound in the front left and center speakers (not on all other speakers).This started to happen after nearly two months without using the receiver, stored in the house so no extreme weather condition.What I have done so far to isolate the problem: inverted my front speakers (noise still appears on the front left output), inverted the front outputs (speaker and cabling inverted, noise still appears on the front left output), disconnected front left and center output (no noise of course, and somehow the receiver doesn't shut off, works normally).Please note that I can watch a complete movie without any problem, no matter the volume level, for as long as I don't pause/play the track...I suspect a problem on the center and front left channels. I have opened the receiver today and re-soldered all the soldering points on the outputs board. This did not make any improvement.Do you have any idea of what component I should look at or test?Thanks a lot for your help,Guillaume

author: coromonadalix
author_rank: Super Contributor
timestamp: August 30, 2018, 09:55:18 am
content: Check when that happens if you have an dc voltage going out to the speakers ... in normal operation volume at zero or when you have sound output ? To be sure the speaker protection systems is not triggering for nothing.service manual :https://elektrotanya.com/onkyo_tx-nr636.pdf/download.html--- had to download twice, the first was zero bytesThe amps sections are bias adjustable .... thats nice ...

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 30, 2018, 10:15:20 am
content: Dollars to doughnuts its a leaky muting transistor. Fairly common problem on most brands. Receiver goes to mute that channel while changing sources, the trigger voltage to the base or gate of the transistor leaks through, DC ripples through to that channel's output.

author: vef445
author_rank: Contributor
timestamp: August 30, 2018, 10:18:55 am
content: Quote from: coromonadalix on August 30, 2018, 09:55:18 amThanks for your answerI do have DC going to the speakers when that happens, both when volume is at 0 or with sound out (the volume doesn't have any impact, exact same result).

author: vef445
author_rank: Contributor
timestamp: August 30, 2018, 10:20:52 am
content: Quote from: mzacharias on August 30, 2018, 10:15:20 amDo you have any idea on how I can find these transistors on my receiver?

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 30, 2018, 09:04:26 pm
content: Quote from: vef445 on August 30, 2018, 10:20:52 amThis is exactly what electronic troubleshooting consists of.1. You identify the symptom.2. You gain at least a block-diagram understanding of the circuit involved for conceptual purposes. (This part has been simplified for you already)3. You examine the service data and try to identify those parts of the circuit to test, which might pertain to your problem.4. One proceeds to use test equipment (in this case probably using just a multimeter) to confirm that a given part is faulty. In this case, a DC voltage will appear at the collector, drain etc of the transistor used for muting because the base or gate junction is leaky. I would look (electrically) near the input stage of that amp channel, but the part involved may for example be on the main board where an amp board plugs in. Normally the muting voltage will be NEGATIVE with respect to chassis ground. It is the large negative shut-off voltage to the device that is leaking through.In theory, this is easy stuff. In practice, access to suspect parts may be difficult. The part involved may be a surface mount device. You may need a fine sharp probe to make your reading.Welcome to the exciting world of electronic repair.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 30, 2018, 10:12:54 pm
content: @ mzacharias you jump to conclusions too fast on your section 4, the dc component at the output may go positive or negative, and not necessarily an leaky component etc ...I've seen protections systems going bad, and the amplifier never had any problems@vef445 you have procedures check number 3 and 4 ( pages 14 and 15 ) of the service manualDo the checks in order and report back

author: vef445
author_rank: Contributor
timestamp: August 31, 2018, 11:54:31 am
content: Thank you very much all for your messages. Indeed, I am no expert in electronic as you noticed, but I am familiar with troubleshooting things that don't work so I'm hoping I get moving in the right direction with a little helpI will do the testing documented page 14 and 15 when I return home and post my results here.I also just realized that all diagrams are part of the PDF linked earlier, which wasn't the case the first time I downloaded it (I guess I had a corrupted download), I'm sure that will help out

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 31, 2018, 12:26:33 pm
content: Quote from: coromonadalix on August 30, 2018, 10:12:54 pmI should have been more clear.In my experience - over twenty years with this type of muting circuits, and 40 years of audio service overall, the "un-muting" voltage to the base or gate would usually be negative, so that the transistor, which is placed across the signal line, is shut off HARD.In fact, special transistors are used because the reverse bias to the base is larger than most signal transistors can handle.It is this reverse bias, leaking from base to collector when the transistor is supposed to be OFF, that leaks through.For this reason, most DC offsets CAUSED BY MUTING TRANSISTORS are negative in polarity.

author: mzacharias
author_rank: Frequent Contributor
timestamp: August 31, 2018, 06:20:15 pm
content: I see a number of muting transistors on page 29 of the PDF. They are arranged thusly.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 01, 2018, 03:10:26 am
content: Quote from: mzacharias on August 31, 2018, 12:26:33 pmWell i have 30 years of audio repairs too, i wont start a fight, but an protection circuit will work with negatives and positives voltages, the important fact is : to protect the speakers from dc component, that's all.On p30 you follow the vpro signal lines up to q6451 and q6452, they will trigger q6453 and give an signal into the vprotect line up to p37 to the micom controller (the brain) pin 130.@vef445 have you done your tests ?

author: coromonadalix
author_rank: Super Contributor
timestamp: September 01, 2018, 03:12:42 am
content: Quote from: mzacharias on August 31, 2018, 06:20:15 pmThis arrangement is to be sure it kill any audio source by an double muting circuit, I have seen it on many brands.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 01, 2018, 04:22:41 am
content: Is there a firmware update available for it? Some funny things can happen when the PLL resyncs, triggered only under specific conditions. A software or firmware change in the source device can change how its output behaves!

author: vef445
author_rank: Contributor
timestamp: September 01, 2018, 08:54:23 am
content: So, I have just done the test 3 (voltage protection) and the result is "NG" plus a timer... I'm really not sure how to interpret thatI need to find 3ohm and 1ohm loads to proceed to the Amp test...Oh, and the receiver is updated to the last available firmware version.

author: vef445
author_rank: Contributor
timestamp: September 01, 2018, 09:24:07 am
content: Here is a video of the test, just so you can see the result (and see if I'm doing something wrong...):

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 01, 2018, 11:55:09 pm
content: Well i have 30 years of audio repairs too, i wont start a fight, but an protection circuit will work with negatives and positives voltages, the important fact is : to protect the speakers from dc component, that's all.Yes the protection circuit will respond to positive or negative at the amplifier output. DUH.I never said otherwise.Sheesh.I was referring to the fault at the muting transistors which causes the offset. THAT FAULT is caused by (usually) a negative voltage leaking through the transistor.GENERALLY this will also cause a negative offset from the amp as well.

author: vef445
author_rank: Contributor
timestamp: September 02, 2018, 06:18:01 am
content: So, all tests are positive, protections work as they should, which I'm not surprised about since I can clearly hear and see (voltmeter) the voltage pic before the receiver shut off.I guess I have to find the transistors pointed earlier in this post as being muting transistors and test them one by one?

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 02, 2018, 01:19:35 pm
content: Quote from: vef445 on September 02, 2018, 06:18:01 amIn this case, I feel the test would be to identify the malfunctioning channel - and just replace the appropriate transistors on that channel as shown in the service data. Given the high likelihood this is your problem, I feel it would be appropriate just to replace them. There are two for each channel.They are surface mount devices, and a major dis-assembly will no doubt be required.

author: vef445
author_rank: Contributor
timestamp: September 03, 2018, 06:26:38 am
content: Quote from: mzacharias on September 02, 2018, 01:19:35 pmThanks for the reply:) I'm not so concerned by disassemble the receiver, I already did most of it when I re-soldered the output board.Can you confirm we are talking here about the transistors marked Q410X and Q411X on the attached diagram?

author: vef445
author_rank: Contributor
timestamp: September 03, 2018, 06:55:02 am
content: And if I'm looking at the right component, I can see that they are using a RTAN430C which I can't find online but it's indicated a replacement part RN1441. Would the following be of a good fit?https://www.mouser.dk/ProductDetail/Toshiba/RN1441ATE85LF?qs=%2fha2pyFadugsbhVQaX8L8rYXi2U42oWKQNSDaZI%2fYbk%3d

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 03, 2018, 11:47:38 am
content: Quote from: vef445 on September 03, 2018, 06:26:38 amI don't believe you ever told me exactly which channel had the fault, so I can't say for sure which exact transistors.The ones that correspond to the channel triggering the shut-down are in turn, the ones that need to be replaced.

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 03, 2018, 11:48:42 am
content: Quote from: vef445 on September 03, 2018, 06:55:02 amI cannot vouch for the cross reference given by some web-site, but it looks legitimate.

author: vef445
author_rank: Contributor
timestamp: September 04, 2018, 05:54:06 am
content: Actually, the cross reference comes from Onkyo documentation, so I'll go for it and order a few of these transistors

author: vef445
author_rank: Contributor
timestamp: September 07, 2018, 04:00:10 pm
content: So, I received the replacement transistors today, opened the receiver and replaced two of them (Q4100 and Q4102 for FL and C output, Q4110 and Q4112 do not exist on the TX-NR636).No more cracking sound when switching input or changing music track and the receiver does not go into protection at that moment: everything works as it should!Thank you very much for your help, I wouldn't have found alone what components to change

author: coromonadalix
author_rank: Super Contributor
timestamp: September 07, 2018, 08:51:52 pm
content: Glad for you

author: mzacharias
author_rank: Frequent Contributor
timestamp: September 08, 2018, 12:30:07 am
content: Quote from: vef445 on September 07, 2018, 04:00:10 pmGlad that worked out for you. These days component level repairs are more and more rare.