Amp4 fried, need some tips

[teflondon]

Hi all,

had this posted up the other day but it got mistakenly deleted for spam.

My amp4 had been working well. Then, while trying to hook up my mv02 to it's own power supply while the mv02 was in the front panel, I got a bad hum. I unhooked the AC wires to the little 14v psu, let them drop, and turned the main power back on. Like an idiot. So 15v ac got shorted to ground. Actually, to the bottom panel of the chassis as I have since realized that the bottom panel isnt in contact with the front and back panel.

The 2050 chip instantly started smoking and snapping. I have since replaced the 2050, which was the only visibly damaged component.

Then I (foolishly?) just powered the amp back on with J5 and J10 closed and nothing happened.

I opened J10 and J5, and measured:

A. 5v at J4 Pin 7 to J3 Pin 4

B. 9.7v at Q10 to gnd, and

C. 8.0v at Q10 to agnd.

With J10 open and J5 closed I measured:

A. 38mv at 4 Pin 7 to J3 Pin 4

B. 7.7v at Q10 to gnd, and

C. 1.8v at Q10 to agnd.


I am not sure if Q10 is supposed to be measured to gnd or agnd. The schematic makes it look to me like it should be agnd.

Anyone have any input on the above readings?

Thanks in advance, and I am going nuts with my stupidity.

By the way, that low temp solder is brilliant for removing components. It's so easy anyone can do it!

[teflondon]

Looking at the schematic for things that could be fried in the 5v path, it seems like it could be anything.

Tomorrow I am going to check U10, U11 and U12 because the relay wasn't tripping when J10 was still closed.

Could the 2001 chip be shorted? The Board LEDs? The LED drivers???

I have so much to learn.

[teflondon]

Does anyone know where to get the TC200x in the USA? I am going to test it tomorrow to see if that is blown.

[krilli]

1) It is entirely possible that I was the one that banned you as spammer. By complete accident. I don't know. I'd like to apologize just in case

2) This sounds a little similar to an Amp4 I managed to mess up. In that case, I believe I managed to blow the 5V regulator. Let me have a little bit better look at the schematics and I'll try to remember.

3) You might have better luck in finding a TC2001 in Hong Kong or China, if they don't show up at the US sites.

[teflondon]

Went over the board with a fine tooth comb today.

I unhooked pin 21 on the TC2001 to see if I still got the short. I did.

The voltages were all screwy on all the pins when I reconnected that pin.

I checked the voltages on the regulators with J5 open, and they all checked out. I started going through the BOM and noticed L5, which is nowhere to be seen on the schematics. I had read the other day that it was not in it and didn't think much more about it.

I looked at L5 under super high magnification (we have a great scope at work!) and saw it was blown out.

I found a bin at work with all sorts of little ferrites and I need to know what I can substitute (if at all) since we don't have any 60ohm 300ma. I assume the 3000ma in the BOM is incorrect!

I have also been trying to log into the store for days now and am not getting in. I have read some posts about there being problems. I can't log into my old account or create a new one, or even get an email with my forgotten password.

Is there a new ACCURATE schematic floating around here?

[V-bro]

You can for testing purposes replace the L5 inductor for a resistor or just a piece of wire. As far as I know they barely have inductance, and therefore the 3000mA might be the real value afterall...

I can highly recommend to get some Chipquik to be able to take the TC2001 off in one piece and see how the 5V goes then, and maybe replace it to see what happens. Its really one of the most useful tools around mate. If it aint broken you can still use it afterwards....

[teflondon]

V-Bro!

Yup followed your advice and quick chipped the 2001 off. That got rid of the short.

I also replaced 4 of the .1uf caps next to the 2050.

Now I just need to find a tc2001 that will be shipped here in less than 3 weeks from china.

So frustrated but not going to quit.

[V-bro]

Alright then, good chance it will work after this!

[teflondon]

Just ordered one from ebay, delivery estimated between March 15 and March 25!

I see the TC2000 is listed in the shop here again. Sure wish I could log in or even make a new account.

[teflondon]

Hey Gang,

Still waiting on my tc2001.

In the meantime, I need to replace the ferrite. The BOM states that the values are 60ohm, 3000mA, with specs of 50 to 100 ohm at 100mhz.

So it seems I can use any ferrite which is 50-100 ohms at 100mhz. What current value can I use? I have some at work which are around 60ohms at 100mhz, but I can't remember the current ratings off hand.

Thanks in advance for the input!