Question about TDA7293 and power module

Rotus623

Member
2010-09-20 4:34 am
I have been having problems with this module, and blowing fuses. If the module is NOT plugged in, I do not blow fuses, if it is plugged in, I blow a fuse and fry the $4 IC that is on the board, and then have to solder a new one (which has 15 legs and is top and bottom mounted, so it is a real pain in the neck).
 

ashok

Member
2002-06-06 4:43 am
3RS
If you look at the data sheet of the TDA7293 you will find that pin8 of the chip is the -ve supply of the signal ( input) section . So no connection of that pin means it will not work. The TDA's also seem to blow easily if the supplies are not correct or missing !

Connect pin 8 to pin 15 which is the -ve supply pin of the IC's power stage.
First look at the data sheet to understand what you are doing. You will find it at Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view . Use a small guage hook up wire to do this. Single strand wire might be most suitable. Make sure that you don't short any other connections.
 

ashok

Member
2002-06-06 4:43 am
3RS
Let's look at this again.
You say :
1. Pin8 of the IC is not soldered on the top of the board.
2. Pin 8 of the chip is soldered on the bottom.
3. That soldered point goes to one cable on your long connector ?

Now check that connection on the MAIN board and see if it has a -ve voltage on it which must be equal to what is supplied to pin 15 on the chip. It could be a bit more negative than pin 15 but must NEVER be more positive than pin 15.
For example if pin 15 is -30 volts then pin8 must be -30 or lower like -35 V etc. But never -28V ( for eg. ).

Maybe something is wrong on the main board supply points ? Check everything several times before reconnecting. READ the IC data sheet a couple of times before doing anything.

NOW: What do you mean by "........Pin 8 is also attached to the main ground board on the chip. Does that have to be grounded directly to chassis, or should i use a plastic washer behind the IC before screwing it into the chassis for support?....."

Is pin 8 " GROUNDED" ? This IS WRONG unless the whole system runs on a single supply +V and ground and not on a +/- split supply.

ALWAYS use an insulated mica or silicone washer behind the chip with a little silicone grease also on both sides of the insulator . If you didn't you might be killing the supply too. I think the metal tab on the chip is connecetd to -V and if your chassis is grounded , not using an insulator is like shorting the - supply to ground ! So maybe your pin8 worry might not be an issue at all !

Also ,the insulator is heat conducting and should be mica or silicone rubber ( designed for this ) or Kapton. Any plastic WILL NOT DO !

Cheers.
 
Last edited:
Whether it needs to be or not, soldering both sides of the board will hurt nothing and you can move on. The unsoldered top? If there is a trace going from it, then solder it. Unless you have worn them out, the holes are plate throughs anyway, so solder one side and both sides are connected. You will note there are several holes on top and on bottom that have no trace leading away. You want to solder them anyway for mechanical strength, but electrically is matters not if they don;'t connect to anything.

Some of those amp models have a grounded heatsink and some insulate it from chassis with plastic washers, I forget which. If you change the IC and leave out the mica washer, then your tab is grounded, and that might explain the whole thing. Power off, unplug the module. Is there continuity between the heat sink and chassis? If there is, you MUST insulate the IC from the heat sink.

Ground board? Do you mean the mounting tab of the IC?