Sony STR-DN1030 Distorted audio when Volume adjusted

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

I think you misunderstand what I was saying about the 1khz input. You mentioned that you have distortion in the original post. What does that mean? Further, you indicate that you have good sound out of all channels other than FL.... that means you are able to input sound somewhere and output it somewhere... so that is what I am asking you to do. Input a 1khz sound (from a computer file / cd disc / dvd audio setup disc... whatever). Look at that input on your scope to ensure that you are reading exactly what is being input (it should look like a nice sound wave with known frequency and voltage specification). Then look at the resulting output wave form on both a good channel and the bad channel. What characteristic is your scope showing.... that is what I am referring to. From that, this will tell us what the "distortion" that you are conveying... ie. voltage clipping, square wave, no wave, no set frequency, what.

Further, the FL and R are only on ic701 so you likely only need to be concerned with those.

Hopefully, your scope view of the output will provide more information to add to your observation about loudness of the bad versus others.

Further note, that the tests suggested on IC701 were just samples... as mentioned, other strategic points can be used to compare across R and L circuits to look for differences.

Working on this. Just a quick clarification question.. the speaker output is what I was going to connect to the oscilloscope. The - output is not connected to ground / Com on the amplifier. Is it ok to connect it to the ground lead of the Oscilloscope? I wanted to hook FL and FR to the Scope and by doing so, both - (black) connectors are tied together and to ground. Just making sure that's ok before I short it out

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

I think you need to ensure that you are connecting your probes reference to a ground point. This usually should be the chassis. I use a handheld scope so I don't have to worry about "ground issues" which happens with "line supplied scope" and the need for isolation.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

I think you need to ensure that you are connecting your probes reference to a ground point. This usually should be the chassis. I use a handheld scope so I don't have to worry about "ground issues" which happens with "line supplied scope" and the need for isolation.

So scope lead is looking at + pin of a speaker and the ground lead connected to chassis of the amplifier. We're not looking at the - speaker out, but I'll just run the test twice one with positive and one with negative with Input is a reference channel showing on both.

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

should be ok (ignoring the -ve speaker) but you can look at it if you want just in case something is going on there. Check both ac and dc coupling just in case there happens to be significant DC coming from somewhere (again shouldn't be but). What are you using for your source 1k signal?

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Make sure you have the probe grounded. Do NOT get the idea to hook a regular oscilloscope up to the hot side of a power supply, unless you are using an isolation transformer on the device under test. If you are not sure, just put a DMM a between the point you want to test and the GND pin on the oscilloscope.

Sounds like you guys made a bit of headway. I don’t think there’s DC on the output, because it isn’t in protection mode!?

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Ok, so here is a movie of what's happening. Channel 1 is a beautiful sine wave 300 mV pk.

Channel 2 is connected to FL (Bad Channel) + pin (speaker out +)
Video starts at Volume level 1 out of max 72 (from MIN volume to 1 it jumps that high in amplitude)

Video shows as I increase volume gradually from 1 to 72. Notice Amplitude simply drops then back constant level. This is the distortion I hear. So there is no linear amplitude increase, and discontinuous as I adjust volume up and down.
Can't seem to upload video.. Can someone confirm they can see this:
https://www.dropbox.com/s/nntf6d3x7j...61555.mp4?dl=0


This is a FR (Good channel). Exact same setup as above. Starting volume level is 32!!! it's barely showing amplitude vs. the bad channel.
https://www.dropbox.com/s/wy86xmkh4n...61820.mp4?dl=0

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

So I tapped into the following pins of IC701:
FL bad Channel:
Pin 2 Vout1+
Pin5 NF1
Pin 6 IN1 (directly from the microprocessor IC400 Pin 14 FLOUT, page 32)

FR Good Channel:
Pin 12 Vout2+
Pin 9 NF2
Pin 8 IN2

Good channel acts as expected; input from uP is small amplitude and grows with vol Up

Bad Channel has the same amplitude jitter and does not increase in volume with volume up action.

DOes that mean IC 400 is bad?? could it be anything else??

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

good work... that was the next suggestion (ie. use some "tapping wires" or equivalent to get access to some "strategic areas safely" (ie. without danger of shorting or otherwise).

the question is how are you inputting your "source signal". Have you checked it? I haven't traced that area yet.

It would appear that you are close...IC400 might have an issue...maybe, since a quick look suggested multiple inputs are fed to the same point of "FXin".

Actually, your "direct in"... isn't so direct, the paths go thru a cap (and some "biasing network") which could be bad.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

good work... that was the next suggestion (ie. use some "tapping wires" or equivalent to get access to some "strategic areas safely" (ie. without danger of shorting or otherwise).

the question is how are you inputting your "source signal". Have you checked it? I haven't traced that area yet.

It would appear that you are close...IC400 might have an issue...maybe, since a quick look suggested multiple inputs are fed to the same point of "FXin".

Actually, your "direct in"... isn't so direct, the paths go thru a cap which could be bad.

Source is a function generator into 50 ohm load routed to SA-CD/CD. note the signal gets to all channels fine except FL (Bad channel)
Cap tested ok with a cap meter. Would a bad cap result in no amplitude range from IC400? Worth replacing based on data?

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Compare C760 to C710. The caps are in series! So IC400 audio goes straight to negative of the caps and comes out on the positive. If C710 is bad, it will diminish your audio volume drastically down next to nothing. IF that cap is bad, change them all on the other channels.

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Also compare pin 51 and pin 52 (inputs to the input selector) on IC400. Make sure the source is on the SA-CD / audio in input and the selector is properly set. Also compare the input pins to the output on the negative side on above mentioned caps, or directly on IC400...
You're doing good!

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Source is a function generator into 50 ohm load routed to SA-CD/CD. note the signal gets to all channels fine except FL (Bad channel)
Cap tested ok with a cap meter. Would a bad cap result in no amplitude range from IC400? Worth replacing based on data?

There is a "swath" of capacitors associated with some sort of "biasing" of the inputs to the ic701. As suggested by capleaker, you likely need to start checking a few.

Actually, you could try removing c710 which would then isolate the ic400 from anything else (in terms of output signal). Then use a "tap wire" and scope the signal therein. IF it is "reasonable" (remember its "unloaded" at this point), then you know your problem is towards ic701 and "pre-circuit" issue. Otherwise, you are likely looking towards ic400.

Further, what are the chances that "NF1" stands for "negative feedback"... :-) maybe check cap c704.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

C710 replaced no change.
Removing it now

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Ok...removed c710 and tapped into the IC400 Pin 14. Though amplitude unloaded is lower, it shows the same amplitude jitter and no change to amplitude with Volume up.

Seems IC400 needs to be replaced. Here is the sad part, it is BD3470KS2 from what i can see and it doesn't seem to be available anywhere... all this work for nothing, maybe. I learned a lot! Thanks for the help and if anyone has leads, please let me know

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Did you do post #51 & #52?
Unfortunately input selectors can be very hard to find. Same was the case with my Sony that I tried to repair years ago and at the end it had a MCU problem too.

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

NOT so fast.... there is more to this than "in and out". Nothing is "straight forward" unless you have selected "straight thru", otherwise even though you think its "in and out" simply... it might go in on the SACCD BUT it might come out and go to processing AND come BACK. The coming back might not be any good... you said "signal gets to all channels fine except FL"... but what's "all channels", you are only inputting on a "source" that only has FR / FL in, so you should only see output on FR / FL and even that might still NOT be only JUST FR/FL "plain".... depending on settings.

You need to find a way to look at pins 75/76 on ic400 to see what's "inside" IC400 BEFORE processing.... carefully. Go from the result....

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Also compare pin 51 and pin 52 (inputs to the input selector) on IC400. Make sure the source is on the SA-CD / audio in input and the selector is properly set. Also compare the input pins to the output on the negative side on above mentioned caps, or directly on IC400...
You're doing good!

Confused a bit here.. are you suggesting that input is not coming to the proceesor right, maybe? Due to damage in the SA-CD / CD circuit? So i can test this by testing a different input path (Say TV Audio Input)?

If my understanding is correct, IC400 Pin 14 is behaving the same with TV INPUT (same amplitde jitter and no volume change)

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

NOT so fast.... there is more to this than "in and out". Nothing is "straight forward" unless you have selected "straight thru", otherwise even though you think its "in and out" simply... it might go in on the SACCD BUT it might come out and go to processing AND come BACK. The coming back might not be any good... you said "signal gets to all channels fine except FL"... but what's "all channels", you are only inputting on a "source" that only has FR / FL in, so you should only see output on FR / FL and even that might still NOT be only JUST FR/FL "plain".... depending on settings.

You need to find a way to look at pins 75/76 on ic400 to see what's "inside" IC400 BEFORE processing.... carefully. Go from the result....

I have selected straight through (A. Direct ?) and same result. Just for my understanding, IC400is what adjusts gain of signal going to amplifier. So if IC400 gain adjustment jumps from zero to almost full scale from Vol Min to 1 out of 72 .. doesnt that suggest the problem is with ic400? Even if input is not 100% good, I would expect gain adjustment to do something at output of IC400. Wrong?

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

OK.... possibly about your "straight" selection didn't change anything.... but unless you know the design "exactly", it is possibly that "straight" doesn't necessarily mean "not touched". Anyway, I think IC400 doesn't do anything with the "gain", IC400 is a "selector unit" which switches things from the input to output for processing / control. I think you need to check things further as suggested. My guess is you have a potential problem with processing and or groundings may be.... plus I think you may have more than one problem (ie. "onion skin").

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

I don't mind drilling further.. I'll tap into 75 / 76 pins of IC400.

My comment on Volume control is based on page 17 of the manual and block diagram of the IC. Seems volume data & Volume clock goes from IC2105 to IC400, and block diagram of IC shows gain stage of 0 to +20 dB before it goes to output pins.

Yeah I'm not sure what Direct is for sure. So I'll keep drilling.