Sony STR-DN1030 Distorted audio when Volume adjusted

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Fix that what you know isn’t right then go from there. I am not a shotgun fan as such.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

When replacing transistors volts on base / emitter is important. Hfe is important too. Depending on circuit, you might even want to match them! In this circuit I can see you don't need a perfectly matched pair. But I really wouldn't an NPN and PNP pair together that has a 100% difference in gain. I know of circuits where the Hfe on transistors went so low due to age, that the circuit stopped working as designed. But if I would measure the transistor in diode mode, I couldn't tell the difference and things looked good. It only came about until I took the transistor out and started to measure hfe. Depending on circuit, yes, hfe does matter, specifically in parallel as one works harder than the other.
I've seen amps where the NPN and PNP pair were quite a bit off between them, but not like 100% off. That data sheet would suggest like 250% difference between that model what would be considered normal. Most other transistor data sheets do that too or even leave the maximum out. Look at a MJE15032.
If you want to shotgun things you'd need to replace a few resistors and a preamp stage too. If you really wanna know what's going on and why, an oscilloscope is your best friend.

I'd love to know what's going on.. however with the stacked boards assembled it's fairly tough to probe the main board without shorting the heck out of everything. So that's the risk I'm trying to avoid. But I do have an Oscilloscope!

Are the smaller transistors and their associated resistors what you're referring to as "Pre-Amp"? resistor values were checked to be within tolerance so that leaves the 2 small-sig transistors? Anything in particular that I have to get, since the SONY part numbers don't have good manufacturer number cross-reference?

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

When replacing transistors volts on base / emitter is important. Hfe is important too. Depending on circuit, you might even want to match them! In this circuit I can see you don’t need a perfectly matched pair. But I really wouldn’t an NPN and PNP pair together that has a 100% difference in gain. I know of circuits where the Hfe on transistors went so low due to age, that the circuit stopped working as designed. But if I would measure the transistor in diode mode, I couldn’t tell the difference and things looked good. It only came about until I took the transistor out and started to measure hfe. Depending on circuit, yes, hfe does matter, specifically in parallel as one works harder than the other.
I’ve seen amps where the NPN and PNP pair were quite a bit off between them, but not like 100% off. That data sheet would suggest like 250% difference between that model what would be considered normal. Most other transistor data sheets do that too or even leave the maximum out. Look at a MJE15032.
If you want to shotgun things you’d need to replace a few resistors and a preamp stage too. If you really wanna know what’s going on and why, an oscilloscope is your best friend.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

These transistors are no longer manufactured by sanken, so who manufactured the ones you got?

The Sony sub part number was 8-749-010-26 (MP1620-OPY-M) and 8-749-010-25 (MN2488-OPY-M)

When I try to see what these Sony Numbers translate to as far as manufacturer numbers, I see them listen as, for example: 8-749-010-26 is MP1620 with O, or Y, or P marking on the parts. All of these are very different hfe.

See:
https://www.genuinereplacementparts....kaAgdtEALw_wcB
https://www.unlimitedapplianceparts....-8-749-010-26/
https://www.amazon.com/-/es/Sony-OEM.../dp/B00FZXHHCQ

They treat these hfe differences as unimportant!

So is there a way to know what 8-749-010-26 is for a Sanken manufacturer number? which hfe is this number?

I'm going by the marking on the part I removed, which is Y. The one I erroneously installed is making P (less hfe.) I've ordered the Y. Do you think this is the smoking gun?

Y marking (the one use on all other channels as hfe range of 15,000 - 30,000
The P marking (the one I accidently installed) has hfe of 6,500-20,000

You'd think the distortion should not happen just because of this?

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

I had to match mine up, because the originals were not available for a long time (45 years) and the replacements I've chosen had a pretty wide hfe span. It's just an example I had to go through for one old amp I had to go through. I just hope this time you get the right ones.
So the MN2488 is exact the same than it supposed to be? It's just the MP1620 that was / is wrong?

Yes, based on the markings on the part

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

These transistors are no longer manufactured by sanken, so who manufactured the ones you got?

The Sony sub part number was 8-749-010-26 (MP1620-OPY-M) and 8-749-010-25 (MN2488-OPY-M)

I am buying Sanken parts from Ebay.

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

I had to match mine up, because the originals were not available for a long time (45 years) and the replacements I've chosen had a pretty wide hfe span. It's just an example I had to go through for one old amp I had to go through. I just hope this time you get the right ones.
So the MN2488 is exact the same than it supposed to be? It's just the MP1620 that was / is wrong?

[R_J]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

These transistors are no longer manufactured by sanken, so who manufactured the ones you got?

The Sony sub part number was 8-749-010-26 (MP1620-OPY-M) and 8-749-010-25 (MN2488-OPY-M)

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Yep, it's a dumb mistake that can very easily happen as not always folks are aware about the gain value (hfe).
When I source replacement transistors with something else than stock, in one case I bought 25 pieces and matched a pair to the original spec on the working channel, then made another matched pair and exchanged the other channel too. I think the transistors also had to be backwards mounted, since the leg configuration was opposite, but that didn't matter, since there was no heat sink involved.
So when you did the transistor pair (NPN and PNP), where they both having different gains, or just one transistor?

Sorry, I don't understand the question. I simply bought a pair on eBay, not sure matched or not, but I didn't notice the hfe rating. The current system on all channels, they seem to use -P option for MN2488, and -Y for MP1620

Do I need to match these and if so what do I need to do? is it impedance measurement? I just ordered one MP1620-Y

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Yep, it's a dumb mistake that can very easily happen as not always folks are aware about the gain value (hfe).
When I source replacement transistors with something else than stock, in one case I bought 25 pieces and matched a pair to the original spec on the working channel, then made another matched pair and exchanged the other channel too. I think the transistors also had to be backwards mounted, since the leg configuration was opposite, but that didn't matter, since there was no heat sink involved.
So when you did the transistor pair (NPN and PNP), where they both having different gains, or just one transistor?

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Actually... I think you're on to something. The datasheet for the MP1620 is cryptic, but it sure shows i got the wrong part. The MP1620 should have been -Y, but i seem to have gotten -P installed... -Y is on order. Hope that does it. I will keep you updated. Thank you!

[R_J]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

If R709 was open, you need to look at how it would open, Q703 would short C~B so +59 volts was likely on the base. so I would check and compare the values of R707,706,708 and Q701,702, if they seem to be ok, the next path is through ic701

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

The only other thing I can think of is that the replacement didn’t have the exact part number. For example: A 2SA1164 has three different versions in which the gain rating is totally different. So a 2SA1164-GR has like three times the gain than a 2SA1164-O.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

One option would be to swap the new parts between the L and R channels.

Thanks.. certainly an option - these boards are so cheaply made though, it's very easy to lift a pad and I'm trying to avoid that if I can.

[frankusb]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

One option would be to swap the new parts between the L and R channels.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

There are only slight impedance differences between the channels. Only thing i can think of the large transistors i bought on eBay, though listed as new, the leads were tinned. Guess i can replace those again?

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

That tells you the problem is somewhere in the PA. Nice thing is that you can compare the left channel to the right channel and go through each amplifying stage. The subwoofer output bypasses the PA stage totally, which indicates there is still a problem of some sort in the PA.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

You should do more tests first. Try all inputs and also switch over to the not used ones. If you get bleed over, let's say input 1 has a CD player on it and switch to input 3 that has notching connected and you still hear the CD player, then the input selector is at fault. You can read and old thread of mine with a Sony strd590 I believe. Try the tuner, the usb inputs etc. to get a better picture. Meanwhile I'll check that service manual out.

Does the subwoofer out distort too? See if the video audio out is clean? That should bypass the amps PA stages.

This thing has a built in signal generator? Turn it on and see what happens.

Might be also worth checking the relays. I don't think ic2105 is the cause.

First finding is that the subwoofer channel does not have the distortion - volume adjusts beautifully

Actually, all output speakers seem to work well, except the "FRONT A" Left and the headphone plug in the front of the unit (which makes sense, as Channel FL is the one the headphones are pulled from.) FL is the channel that was blown when I got the unit. So I don't know if I got bad parts or if there are more bad components on that channel.

Seems (in addition to distortion) as I go from low volume to high the headphones shift to right only and left seems to be shutting off.

Again for that channel, I had to replace Q703, Q704, R713, and R709 (see attached)

[CapLeaker]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

You should do more tests first. Try all inputs and also switch over to the not used ones. If you get bleed over, let’s say input 1 has a CD player on it and switch to input 3 that has notching connected and you still hear the CD player, then the input selector is at fault. You can read and old thread of mine with a Sony strd590 I believe. Try the tuner, the usb inputs etc. to get a better picture. Meanwhile I’ll check that service manual out.

Does the subwoofer out distort too? See if the video audio out is clean? That should bypass the amps PA stages.

This thing has a built in signal generator? Turn it on and see what happens.

Might be also worth checking the relays. I don’t think ic2105 is the cause.

[jason123]

Re: Sony STR-DN1030 Distorted audio when Volume adjusted

Well, if that's the case you need to go through all the amplifying stages. You may have to take transistors out too and measure the hfi gain. Also look at the input stages, make sure levels are equal.

Could you please look at Post #10. Am I on the right track?