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Old 1st October 2010, 11:59 PM   #1
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Default Question about TDA7293 and power module

So I bought a power module for the MG100dfx amp, and the #8 pin is NOT soldered at the top, but all other pins are soldered on the top and bottom of the PCB. If anyone has this amp or uses this power module, would you mind seeing if pin #8 is soldered on your power module? Here is a link for reference. As always guys, thanks.....
power module mg100 dfx
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Old 2nd October 2010, 03:43 AM   #2
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Anybody?
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Old 2nd October 2010, 04:19 AM   #3
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Uhmm I'm not particularly familier with that module. But look at the connection lines the green shiny and determine if any of them fall on that pin. Then determine where they go and get back to me I think I can help
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Old 2nd October 2010, 05:00 AM   #4
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Oh yeah, one of the traces run right to that leg. Even if it isn't soldered, the leg runs continuity to where the trace runs from. I am pretty sure that it was supposed to be soldered, but it is very strange to me that it isnt soldered.
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Old 2nd October 2010, 05:02 AM   #5
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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).
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Old 2nd October 2010, 06:25 AM   #6
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Is that with the unsolderd pin soldere2wd or unsoldered
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Old 2nd October 2010, 12:54 PM   #7
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It is with the pin unsoldered, so I figured it needs to be soldered. May have been missed by the factory/preparer. Who knows.
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Old 2nd October 2010, 02:04 PM   #8
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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.
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Old 2nd October 2010, 03:37 PM   #9
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Okay ashok. 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?
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Old 2nd October 2010, 04:03 PM   #10
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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.
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Last edited by ashok; 2nd October 2010 at 04:13 PM.
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