Error hunt: Red Led on. AMP6

[RedStar]

My first build. I'm in phase where you connect resistance to c1819 legs. I used 2Mohm resistance and connected 2*15V 80VA transfomer and measured voltages:
input: 17,1V
C99 22,9V
C1819 14,7V
regulator (center leg) 8,3V

When i switch power on both LEDs are on no matter if sleep is connected or not. And if i keep power on for a while (like 1min) both LEDs slowly turn off. Any idea wheres the problem? Shut green LED even be on before i connect sleep? I'm using switch for the sleep.

[V-bro]

Where did you place this 2Mohm resistance?

On what input do you measure 17,1V?

14,7V on C1819 is not alarming.

Center leg of the regulator should measure the same as it is directly connected to C1819.

I do think 22,9V is a bit high, but it is within the specs of the regulator.

The fact that the red led is on is not good, here's what it says in the AI:"The red led is connected to the Tripath chip FAULT output. It turns on the LED in case the amp is overheated or has experienced over current."

In most cases it means that there's something shorted on the outputs...

The green led should be off when J2 pin 1 and 2 are open, and on when they are closed. This led is connected to overload, so also when the input gets too powerful signal it will be off (responds at the beat so to speak)

Can you show pics of your creation?


------X-max. can be several meters on any driver, too bad it can be done only once...------

[RedStar]

Here is some pics. You can see where 2Mohm resistance is. Is it right? 17,1V AC i measured from transformer (red wires). And sorry - i checked voltage on regulator and it was 14,64V.
http://img265.imageshack.us/img265/4494/image7ja0.jpg
http://img240.imageshack.us/img240/8320/image8fp0.jpg

[V-bro]

Where are the leds?

I see you are in a teststage somewhere? Having not yet placed the chip and coils and C100?

I think you need the chip in place to determine whether the leds function right, but I'd have to have a closer look to the datasheet and schematic to know for sure...

I have never been in such a teststage, I just built it and it worked instantly...

------X-max. can be several meters on any driver, too bad it can be done only once...------

[RedStar]

C100 Is there. It's on other side of the board. Green led is at case front panel and red is back of the case

Jan says in instructions: "Now, you can connect a transformer and check the voltage from the regulator. If it is OK, you can remove test load from C1819 and continue. Do not proceed any further until this test has passed."

That all there is. It does not say anything about LED's but i assume that red LED should not be on. And green LED should only be on after connecting sleep. Am i right?

[V-bro]

It is kinda odd, for as far as I can tell from the schematic both leds should be off.... Now the 2N7000 transistors switch the leds on, both get railvoltage on one end , mute and fault go to the middle pin on the one that switches the red led and overload goes to the middle pin on the other transistor that switches the red led on...

Maybe there's some kind of solder bridge on the transistor pins?

------X-max. can be several meters on any driver, too bad it can be done only once...------

[RedStar]

Thanks for helping, i'm not home so i can't check it out but i'm going home at monday so i test it then and report here if i found the problem.

[RedStar]

There is no solder bridge's at 2N7000 transistors. I measured voltages from those transistors. See picture. After connecting power there is 6V and 9V and then both voltages decreases slowly to 0V. So are these transistors Q1 and Q2 broken?

http://img169.imageshack.us/img169/7103/image10en1.jpg

Edit: Can i continue? Is there any harm for TA2020 if i finnish soldering and test the amplifier?

[Scratchy]

Thanks for posting the schematic RedStar it indicates exactly what the issue is.
The gates of the 2 2N7000 mosfet transistors are normally connected directly to pins on the TA2020. With no chip installed, these gates are not biased & are just floating - a bad thing for fets, as they have very high input impedance. Since there is nothing connected to the gates, the LEDs are not functional and would not indicate whether the AMP is assembled correctly at this time.
From what I understand, the test in the AI does not indicate that you should be checking the LEDs at this point, but merely to check that the voltage regulator is functioning correctly.

***If it was easy, everyone would be doing it***

[RedStar]

Ok that came in my mind but becouse i have so little experience wasn't sure. So everything seems to be as it should be and i will finnish assembling/soldering today. Thanks for help...