speaker hiss

[ShowMaster]

Ok, got a spool of chipQuick .020 63/37 solder.
I'm good

[LTMNO]

Ok, got a spool of chipQuick .020 63/37 solder.
I'm good

Thats the good stuff..

[s_mack]

I use .025 63/37. Even for those tiny parts, it isn't too thick. You made a good choice.

[ShowMaster]

I saw the chipQuick name on the size and decided it was for me. Sadly they don't carry SMD parts so I better not damage any, or like last night, lose any on the bench.
I'd really like to see how all those parts got put on the boards originally? Those robots must have tiny little fingers.
Fortunately I have some really nice pointed tweezers and good magnification. Even then, it's an acquired skill.
I have a time tonight to go at it again.

[s_mack]

The pick and place machines are pretty amazing. And you think these parts are small! I went nowhere near as small as I could have. I think the smallest piece I have on there is an 0402 resistor. The pick and place machine that was used can handle 0201 (1 quarter the size). You can barely see them they are so small! Easily mistaken for dust.

You still have that "spare" kit, right? I've told you before, if you damage anything in the pursuit of troubleshooting... feel free to consider that your backup.

[ShowMaster]

Thanks Steven. Yes I have the kit. I'm finally getting to be glad I have it.
Messed up my back putting up (alone) new replacement solar panels on a charging container at our club field and I'm still hurting. Damn this electric planes and birthdays.

[ShowMaster]

Today I shorted the non CPU side of the 10k in my drawing to ground. To my ear, in my quiet area, all hiss as we're calling it, went away. So did the announce audio.
Next I added a 10k pot to ground basically making a voltage divider. No hiss change until I was almost at ground. The announce audio was very low.
I tried some caps to ground but that also killed the audio or did no good.
It's really looking like it's coming from the CPU as ambient noise and it can't be simply filtered out.
It's still quieter than my Taranis.
I'm open to other ideas while I have wires hanging on the audio traces. I'm going to make a statement here, I don't think it's the audio IC and I can live with it. I will however, not give up trying any ideas others can think of.

[jhsa]

As I mentioned before, and I say again I think we have to find out the frequency of the hiss and filter it right after the procrssor. That might also take an effect on the audio playing of course..

João

[ShowMaster]

The hiss or noise I see on my scope and posted, isn't a sign wave. I'm not sure a simple filter will do any good. Rolling off the audio to get rid of a pulsed square wave with something brute force, may really affect the audio response.
I'll try anyone's ideas. I'll also try the trick of a pot and cap in series from after the10k to ground. As I turn the pot this network should roll off highs and maybe the hiss. My concern is that the highs are what I want while flying. The lows get lost in the outside ambient noise. But so does the hiss I hear.
Again, are those being bothered actually outside flying or in a quiet room?
I'm trying to quiet the hiss I hear because it has come up.

[jhsa]

As far s I know the hiss frequency is above the voice frequency range. A low pass filter could work in my opinion..

João

[ReSt]

Showmaster,
could you try to feed an external amplifier (type D amplifier), an amplifier without any other connections to the radio

Reinhard

[ShowMaster]

I don't have a amp to try.
When the input is grounded to the 9xt amp it's very quiet.

[ShowMaster]

As far s I know the hiss frequency is above the voice frequency range. A low pass filter could work in my opinion..

João

I'm open to trying a low pass circuit. I just haven't designed any to do it.
I was doing some reading on d/a hiss and class D amps.

http://www.microchip.com/forums/m/tm.aspx?m=709339&p=1

http://ww1.microchip.com/downloads/en/D ... adn007.pdf

http://www.analog.com/library/analogDia ... ass_d.html

[MikeB]

Have you got a wire on the amplifier side of the 120K resistor?
If so, a simple thing to try is adding a capacitor to ground at that point. I tried a few, low values (47pF, 82pF) but they didn't have any effect. Such a capacitor should form a low pass filter (6db/octave) with the 13K resistance from the DAC output.

Mike.

[ShowMaster]

I can add a wire there. Ive got to see what caps I still have in my parts box. I can buy some locally from ALL Electronics. A lot of parts, for little $.

[ShowMaster]

Nothing to report. Had some other issues keeping me away from the bench.

Update.
I'm having some back issues requiring therapy. It's kept me from having any fun while I mend. I got hurt installing solar panels on our club field charging station roof. Had to put bench work and Rc flying on hold for a few weeks.
Fortunately this hiss issue is a bother, but doesn't take away from the great flying features the 9Xtreme offers. Hopefully everyone's out flying.

[ShowMaster]

I finally had some R&D time today. The outcome was not productive. The caps that did cut the higher end where I hear any hiss, also reduced the gain. Outside flying, as I've said before, the ambient noise overpowers any hiss, but the high gain audio is desired.
Now the bad news. I managed to I guess, damage the IS31AP2005 audio IC input. I now have distortion.
I was actually connecting caps to pin 4 of the IC via a soldered wire and clips, so no series 120 ohm series resistor for safety.
Not a big deal to replace it if I have another one. I have a second 9XT, that I'm keeping pristine for flying with. I want to to repair and continue to test with this board now that it's the test one.
So where do I buy one or a few, new IS31AP2005 ic's? The shipping and handling costs are over the top for a $.55 IC!
I'm hoping Steven has some parts? Being this was assembled in China, maybe not.
Minor setback while parts shopping. I need the experience anyway on replacing SMD parts I can see with the naked eye ha ha.
Good test for my microscope!

[s_mack]

I could send you a couple proto boards if you want the practice desoldering as well

[ShowMaster]

Thanks Steven. I should try one of your boards for the practice. It depends on you wanting to keep your proto boards?

I think I found the IS31AP2005 at digi key for $.94/ and maybe $3 postage. I think the postage would be the same for several.

[ShowMaster]

I placed a digi key order so I should be good.
Not sure of the final cost of shipping but it's happening.

[ShowMaster]

While I'm waiting for parts.
ChipQuick or hot air to replace the IC? I haven't tried hot air but have the wand.
This is where a practice board world be handy.
What I have Kearney about the IS31AP2005 IC, is you can't shirt pin 4 to ground by accident!

What I did learn as I posted earlier, is the various parts box caps I tried either did nothing, or dropped the audio level along with the hiss. Basically cutting the top end freq response and the hiss. I don't want the reduced volume level!

I'm going to scope the input, pin 4, since I have a wire on the 120K connecting to pin 4 now. Hopefully I'll see this hiss and can still try some more caps. I just can't hear it well due to the distortion now.

[jhsa]

I would definitely go with chip quik..
That thing is amazing

João

[s_mack]

For that tiny chip I'd use hot air. Less cleanup. You should be able to heat up all pins simultaneously and just blow it right off. Just have to be careful with nearby components. Send me an email when you get a sec and confirm your address... I'll get you some practice boards

[ShowMaster]

Super Steven! I reimburse the shipping or ? To help out.
I've been wanting to use my hot air stuff. I wonder if a layer or 2 of aluminum duct tape over the parts I want to NOT melt the solder on would work!
I do have ChipQuick to back me up.

I side note on my hot air wand. I find it great for shrink tubing I did a plastic tx case. Turn the air down low and use a small tube tip.
I'm going to make a brass slip on end that will let me cup the tubing and direct the hot air around it as well as deflect it back up, to avoid melting other things in the vicinity. I just have to remember to have the wand itself vent upwards!
Ok, off to email.

[ShowMaster]

Check PayPal Steven. Let me know if it's ok.

[s_mack]

Thanks. I will get the stuff out today. I meant to do it yesterday, but something came up.

[ShowMaster]

No real pressure, I just wanted to let you know what I did.

[ShowMaster]

Be careful trying to measure or reduce the hiss when working on this board. I'm working on it with Stevens support and a spare. I'm ok with the audio but still looking into it.


I removed the damaged P5204 2005 IC I damaged trying bypass caps. Interesting project.

The hot air removal I gave up on because of the super small parts all around the IC that also got hot and want to unsolder.
I tried chipQuick and I just couldn't loosen the IC? Then I could see the iron heat had pretty much removed the IC leads and the internal metal chip body was still attached solid to the board?
Not wanting to preserve the IC, I chipped away the black IC shell. Inside was the actual part. It was a metal chip.
Heating this remaining internal metal chip with my iron finally allowed me to slide it sideways. That reviewed that it was soldered to a PC trace heat sink under the IC.

I must warn everyone to not blow this IC as it may not be practical to replace without good magnification, I have a smd microscope. I thought I had ordered a replacement IC but it may not be the same? It came with different numbers on it and has no exposed solderable surface on its underside.
I'm now trying to find a p5204 2005 class D audio IC. Steven should be sending me a few boards for parts and I'll try and remove an IC from them with heat. No worries about other parts loosening then. Wow, they're small. I may have met my match, but I'll keep trying.
On the other hand, I could try another IC amp option now that I have a choice. I'm open to what to try?

Here's some pictures of the IC removed. The missing smd cap part was saved and will be replaced.

ImageUploadedByTapatalk1454817008.716960.jpg (28.78 KiB) Viewed 12117 times

[ShowMaster]

This is the IC I have as a replacement for the P5204 2005. It seems to be equivalent but no exposed bottom solderable heat sink. I'm assuming it had one but I can't find this exact number.


What I have and I'll try.

IS31AP2005

http://www.issi.com/WW/pdf/31AP2005.pdf

[ShowMaster]

Not doing well. More my ignorance of working with parts this small. Even with a microscope, doing soldering rework on parts this small is challenging! The IC I did order I find has the wrong pins for attaching to this boards circuit pads, just too big!
I haven't damaged the board, but I may have to wait until I have a real P5204 2005 IC to try.
The fact that it was also soldered to the large circuit trace under the IC, makes me think only an oven or hot air is the answer for this repair. That's complicated by the smd parts so close I may blow off while heating.

None of this is a issue or complaint as long as you install and enjoy using it as its intended. If you do any R&D or battery reversal, repair may be a serious issue due to the part sizes and types.
Hopefully everyone will be careful. This is common for most compact electronics with this parts density.
My point is, install it and enjoy it!

So for now I'm putting this on hold and not damaging the trace, until I can find the correct part and do some practice hot air soldering. Just a setback on my part.
I'm installing the new spare board and doing some fun flying while I rethink my next move.
Good news is no hiss now ha ha! It never bothered me but now it's really gone!