Sound amp testing question

[Belike]

I have a Tutankham pcb with a sound fault, I think it is the LA4460 sound amp broken, but I'm not sure.
I need some input how can I test the sound amp if it is working or not.
Thanks in advance for any inputs.

[Muerto]

Perhaps put a speaker to it
Sorry for goofing around - to answer your question: i don´t know

[Etienne MacGyver]

For about 5 bucks you will know if its broken or not  

http://www.twistywristarcade.com/sound-amps/37-la4460-sound-amp.html

Just swap it dude !  

Now seriously, there must be a way to measure something on that thing, the question is how...

Maybe this pic helps a bit ?
If i get the pic, you should have the "12 volts DC" between pin 1 and 10.

Source: http://www.bucek.name/pdf/la4460,4461.pdf

[polderarcade]

Option 1:You can try putting a speaker against the input(of the amplifier chip) maybe hear a light sound

Option 2: take the input signal and use a cheap separate amplifier to see if you have sound

Option 3: use a scope to see  if there is a signal you also can use a scope to follow the signal.


That are the things I found, have the same problem whit my outrunners pcb some problems in the sound circuits.
Only didn’t have the time to try them al out.
May be its useful

[Belike]

Thanks for the inputs guys, I will try out everything you advised.

[level42]

Here's a scientific one:

- straiten index finger
- move it around the pins of the amp (touching them)
- listen if you hear any changes....


Seriously I used this mehthod to find out that the LM324 on my Centipede was bust

[Belike]

Here's a scientific one:

- straiten index finger
- move it around the pins of the amp (touching them)
- listen if you hear any changes....


Seriously I used this mehthod to find out that the LM324 on my Centipede was bust

First question which one is the index finger?
Touching them means short it with a wire or touch it with the multimeter?
Ah, and does the board have to be powered up?

[Etienne MacGyver]

http://lmgtfy.com/?q=indexfinger  

just touch the pins when its on, and there might be a buzzing noise (brom)

if you listen that, chances that you got a working amp are very high.

if you dont hear anything, you can almost assume its busted.

[Belike]

Lol, I thought index finger is a leg of the amp.

[level42]

LOL !!!

You can also use this finger:



It will work just as well, but it just isn't very nice really is it (although it's great that Feyenoord did so well this year, so this pic is for all those who laughed at us a season ago

[Belike]

Made the finger test and there were absolutely no buzzing or anything else.
Bought some of these amps then, fortunately just 2 eur/piece.
The sound pcb has a huge heat sink and the amp was under it.
Let's light up the soldering station





New amp installed and some toothpaste applied.

Let's hear the result
http://www.youtube.com/watch?v=D_hmvFi2ehw&feature=youtu.be

Thanks guys.

[level42]

Haha, the finger test never fails

Glad you fixed it. That is a bit much "toothpaste". Did you scrape away most of it ?
You really need to get a thin layer. I always scrape it away (using an old screwdriver) that you can see the part through the paste streaks...when you press the part to the heatsink (or screw it again), it will produce a nice thin film...

[Belike]

Thanks for the tip André, my layer is a bit thick indeed, it was my first try with this method.

[Superully]

wonderful, bela, you're getting better by the minute!

eh, can someone school me on the "toothpaste", please?

[Belike]

Normally, there is a layer of a special gel or paste between the heat sink and the processor or amplifier, afaik the components can melt together without this from the extreme high temperature.