Altec Lansing MX5021 silent, need Schematics..

[julius22]

Altec Lansing MX5021 silent, except for some hum.
The output amp ICs seems to work.

Does anybody have schematics for the amplifier in this unit?

[Khron]

What test equipment do you have available?

[julius22]

Hello,
I have a range of multimeters, Oscilloscope, Audio generator, Portable One Plus.

I understand, the "remote" has a 2-wire serial data connection to the amplifier, that communicates with the "TDA7433 Basic Function Audio Processor".

May be the problem is here. (?)

The Power supply seems to be ok.

[Khron]

I was just thinking that if you apply a signal to the input, you could scope it out along the op-amps in the audio path, and see where it stops.

If there's that processor in there, though... There is at least some chance the problem might be somehow related to it. It would definitely be worth scoping its inputs & outputs, though.

http://www.st.com/web/en/resource/te...CD00000878.pdf

[ant3202]

many users feedback that ST TDA7433D seems to fails alot.

im waiting for the parts to come....

[ant3202]

Update, I had replaced the ST L7809CV and JRC 7909A IC chip,
obviously the IC is driving hard, as the PCB board is discolored at that area.
replaced with a fresh IC and added heatsink.

now the audio is back.

[theATeam]

I know this is an old thread, but it is the closest thing to a solution, i have been able to find.

I have two sets of the Altec Lansing's MX5021. One of them doesn't work. The other one still works.

There are two ICs located on the back of the PCB. The first one is ST TDA7433D located at U8, which is partially melted on both of my speaker-sets, but the label is still readable.

The second one is unidentifiable, since it has melted/ deformed to a degree where the model-number is unreadable.

Could anyone tell be the model-number of the IC located at U13 on the back of the PCB?

This would really make my day. I love theses speakers, but i can't find any schematics or high-res pictures of the PCB online.

[Andrew F. Ali]

I don
t think the ICs melt or I've never seen an IC melt before. I think what you are seeing is probably the varnish they spray on finished circuit Bds at the factory. ICs or semi-conductors would pop open and burn.

[theATeam]

I have a few pictures. It may be varnish that covers the first one (U13), but the TDA7433D (U8) looks like it has been too hot.

They designed the speakers so that these two ICs are literally covered in rockwool, so i'd image they can accumulate some heat during longer use.

[Khron]

If heat was indeed an issue for those chips, they would've shown marks in the middle, where the actual silicon die sits, not on the edges

https://thumbs.dreamstime.com/z/ic-r...h-47481330.jpg

That's more likely flux residue, or something external. I doubt they'd bother conformal-coating dry-environment consumer stuff like these.

Either way, the first commandment of troubleshooting electronics is "Thou shalt measure voltages"

[budm]

"the first commandment of troubleshooting electronics is "Thou shalt measure voltages" +10

[ant3202]

Originally Posted by theATeam

I know this is an old thread, but it is the closest thing to a solution, i have been able to find.

I have two sets of the Altec Lansing's MX5021. One of them doesn't work. The other one still works.

There are two ICs located on the back of the PCB. The first one is ST TDA7433D located at U8, which is partially melted on both of my speaker-sets, but the label is still readable.

The second one is unidentifiable, since it has melted/ deformed to a degree where the model-number is unreadable.

Could anyone tell be the model-number of the IC located at U13 on the back of the PCB?

This would really make my day. I love theses speakers, but i can't find any schematics or high-res pictures of the PCB online.

Hi and what issues on the faulty one?
No power or no sound?

U13 - ST 074C
https://www.st.com/resource/en/datasheet/cd00000489.pdf