audio buzz question.

[bozo55]

there should actually be two leads on the op amp that have this voltage. also same on the 22uf cap next to the AV jack op amp.

Thanks Keith.  I let the bitch loop on demo with Devil's Crush for several hours.  Couldn't get it to screw up any more.  I almost want it to screw up so I can test it.  I'm in denial that cleaning it actually fixed it.

[pnauts]

Call me crazy, but I observed this:

More intense/greater amount of "white" (lighter colors) on CRT screen --> more pronounced buzz/high-pitched whine.

Buzzing is not just due to the intensity of "white" displayed on screen...but it is a factor, perhaps.

I am sure the gurus can explain why this happens, in addition to crosstalk (and _____ and _____).

I agree, white is 0.7V level on analog video (the higher voltage) perhaps there is coupling on audio

[bozo55]

I just A-B'd the sound between my TG16 and Duo with Ninja Spirit.  The TG16 is using the original HuCard with RF and the Duo is using the Turbo Everdrive on Composite. 

Both are using the same sound settings on the same TV.

I noticed the Turbo is way way louder than the PCE Duo and has big booming bass in the game.  The Duo sounds tame by comparison.  Is this another sign my system is jacked or is the Duo a quieter console than the original Turbo?

P.S. I tested the voltage on all those points you recommended Keith.  In fact, i started probing just about every cap on the board.  The Audio caps all read 3.8-4v, most of the other caps read 5v.  Some read 7-8 volts.  Most of the op amp pins read 3.8. one read around 8v and pin 4 read 0v.   Voltages seemed to check out fine.  I triple checked cap orientation and values when installing and I still don't see anything wrong with respect to that.

P.S.S. I ordered a genuine Stereo AV cable for the Duo from fleabay.  I will hopefully have it in a week to see if that helps matters.

[Keith Courage]

there is one more thing to try. sounds like a grounding issue due to old cap goop somewhere. It is easiest to tap this fix elsewhere then it is to find the shorted connection. Will pm you instructions shortly.

[bozo55]

there is one more thing to try. sounds like a grounding issue due to old cap goop somewhere. It is easiest to tap this fix elsewhere then it is to find the shorted connection. Will pm you instructions shortly.

Sweet.  Got the PM Keith.  I'm going to try this ASAP and get back to you with the results.  Thanks!!!

[bozo55]

Hey Keith.  So I did the red line method as you suggested.  Here is a pic of the work for your approval/disapproval

http://postimg.org/image/gquiiqd1x/

Checked for shorts with an eye loop and for continuity with a meter.  Everything seems fine.

Alas, the sound issue was not changed.  I am determined to fix this, so please don't hesitate to suggest anything else.  Thanks Keith!

[Keith Courage]

well if that didn't fix it then there definitely has to be shorts or bad traces somewhere.

usually if the chip card volume is being affected as well then it is a problem near the main AV op amp.

try bridging the wire for the ground on the op-amp itself. Sometimes that connection gets sorted out.

I really have a feeling you were going to need to remove said op amp though and clean under it then reinstall. same thing with the op-amp closest to the M 5205 chip.

[bozo55]

well if that didn't fix it then there definitely has to be shorts or bad traces somewhere.

usually if the chip card volume is being affected as well then it is a problem near the main AV op amp.

try bridging the wire for the ground on the op-amp itself. Sometimes that connection gets sorted out.

I really have a feeling you were going to need to remove said op amp though and clean under it then reinstall. same thing with the op-amp closest to the M 5205 chip.

Thanks for the insight Keith.  Is pin 4 of the op amp Ground?  I'm not quite sure.

If I butcher an op amp trying to remove it, will I be able to find a replacement on DigiKey or Mouser or will I be screwed?  I really don't know how I am going to remove the op amp other than fluxing the pins, adding more solder on them and then removing the solder with good ol' solder wick.  Is that a bad idea?

[Keith Courage]

Here is a link to get new ones. http://www.taydaelectronics.com/ic-integrated-circuits/audio-amplifier-instrumentation-op-amp/tjm4558-dual-operational-amplifier-wide-band-soic-8-tjm4558cdt.html

Lots of times you can re-use the old ones though. I pry up slightly under them using a small screw driver while de-soldering one side at a time. Meaning all 4 leads on each side at once.

I'd still look for low voltage somewhere. Double check and wright down the Volts you are getting off the The op-amps and caps when the system is working correctly vs when it is not.

[bozo55]

Here is a link to get new ones. http://www.taydaelectronics.com/ic-integrated-circuits/audio-amplifier-instrumentation-op-amp/tjm4558-dual-operational-amplifier-wide-band-soic-8-tjm4558cdt.html

Lots of times you can re-use the old ones though. I pry up slightly under them using a small screw driver while de-soldering one side at a time. Meaning all 4 leads on each side at once.

I'd still look for low voltage somewhere. Double check and wright down the Volts you are getting off the The op-amps and caps when the system is working correctly vs when it is not.

Thanks Keith.  I think I'm going to order some of these op amps before I try to yank off the old ones just in case . 

[bozo55]

I grew a pair of balls and went for it.  I used a decent sized chisel tip to drag back and forth on each side while prying gently with a pair of tweezers. 

I removed the op amp without incident and cleaned the holy hell out of the board with electronics cleaner spray.  I then tested all the traces to make sure that they were good as well as the vias under the chip.  Everything was perfect.

I reinstalled the chip and the volume stayed the same.  I could still hear faint static on the right channel, but only sometimes and very faint.  The audio buzz is still prominent as a result of having to raise the volume.

I wonder if the headphone volume pot is causing it?  I'm going to remove it and see what happens.  Here's some pics of the work:

http://postimg.org/image/uxkvlklpp/
http://postimg.org/image/ywtrin3pz/

[bozo55]

Woah, the sound went out again.  Happened the same way.  Got distorted, then quieter, then the musical notes just sounded like rhythmic crackles, then the crackles mostly faded out.

That 22uF cap gives me 3.6 volts.

Edit:  Oh shit.  I think I figured out what's going on.  The traces under the AV opamp seem finicky.  When I pressed on the opamp pins with my meter the sound came back.  Specifically around pin 2 and pin 3!

Could this be bad traces or a bad op amp?

I managed to catch this bizarre phenomenon on video, uploading it now:

[pnauts]

bad traces of bad soldering.

[Keith Courage]

yep, op amp traces. remove it and clean the area really good. Then re-install.

Also, sometimes it's just the ground pin in which case you can just tap a new ground from elsewhere on the board.

[bozo55]

yep, op amp traces. remove it and clean the area really good. Then re-install.

Also, sometimes it's just the ground pin in which case you can just tap a new ground from elsewhere on the board.

But I already removed and cleaned them   I have pics showing just how well I cleaned under there.

Even with the sound dead right now pin 4 (V- in) has continuity with ground.  All the pins have voltage readings even with the sound dead.  But when I press on pin 3, shazam it's alive again...