Sony STR-DN1030 Distorted audio when Volume adjusted

[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.

[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!

[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.

[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?

[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

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??

[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

[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!?

[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?

[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

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 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 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.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Started with impedance measurement around IC701. All impedance measurements were referenced to pin 7 (gnd). No significant differences between IC601. Some pins had caps so impedance was fluctuating... but similar to bad channel.

Attempted 1khz sinewave input, however relays were not routing signals unless all boards were connected and that gives almost zero room to probe with 3 board stack.

Finally went for the jugular and swapped ic701 with ic601. Problem remained on the FL channel. Checked resistor and cap values around the IC. All seem to check out.

That leaves post amp circuit? Not sure how that could be it but i am new to this audio stuff so help is very much appreciated

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

capacitor issue maybe. Again, the suggested resistance "probing" may point to an area of difference including ic701.

additionally, with the "new observation", get your scope going. Feed in a 1khz tone of known value. Look at the resulting output characteristic.... voltage / frequency / appearance.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

So, one additional observation that may mean something to you: when the system is playing, Volume level 1 for this FL channel is very high compared to the other channels that you can barely hear anything out of.

Here is today's work:.. swapped main BJTs, Smaller pre-amp ILIMITER (Q702, and Q701) between the FR (Good) to FL. No change. FR still works fine, FL still has issues.

Verified R707, R706, R709, R710 all comparable to FR and match values on schematic.
Seems the only thing that remains unchecked:
Post amp circuit and IC701
Thoughts?

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

As an example of a possible check. do a resistance measurement to ground of the voltage outputs on the IC701 (page 34)... pins 2,3 and 13,14... these are signal outputs going to the subsequent components in the output stages. You can compare the meter readings / response to see if there is significant difference. Go from the result.

Note: if you can't readily get at the IC points move along the diagram to a readily accessible area / component and measure there.

[budwich]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Hopefully, you can get back to having the one working front channel (FR). IF so, before you go further in "tearing apart" your board / components, do some "simple resistance" checks. Unplug / disconnect the receiver from power. Get access to the main board as outlined in the SM (page 33/34) which shows the FR / FL. Choose "wisely" various points to compare a resistance measurement across the two different circuits... you aren't looking for "absolutes"... you are looking for "similar". Yes, I know you indicated you did an "impedance check" but that was likely at the outputs and was a "gross" check of the "entire circuit". The checks that you want to do now, are more "partitioned" to try isolate a group of components / portion of a circuit that you can then focus on specifics (individual components) there after. It might not show anything BUT something could readily pop out. It basically costs nothing other than a bit of time.

The reference points for the checks could be grounds or powering or even in / out lines depending where in the circuit you choose. The thing about doing this method is there is little to no danger in cause damage to the board / circuit (short, breaking track, etc) because nothing is being powered.

Study the circuit diagram to choose your points to isolate / test various sections that can be readily compared across the good and bad front channels. Make notes on what you observe from your meter and which test points you were using at the time.

Since you have "touched" some of the active component, that area might be your first focus.

Hope this helps.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Ok swapped FR transistors to the problematic channel (FL) and distortion is still happening on FL. Resistor values are good. I dont have a way to test small BJTs. Should i replace all smaller BJTs? Any matching there?

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Very unexpected, but i put the "new" part in and now i am getting protection error! Will swap main transistors between left and right and see if that follows the new Y MP1620