AMP11 blown up. Any ideas?

[MickB]

After nearly 2 years of heavy use and abuse the AMP11 in the Bassbomb has died. I wasn't using it myself but I've been told it just suddenly stopped playing half way through a street skate. I've taken it apart and found that a couple of legs on the TP2050 IC (actually an STA505 in this case) have been blown off. Any idea what might have caused it? There's no other obvious damage anywhere and nothing wrong with the wiring or anything else. It's powered by a 24V nominal battery and the 4A slow blow fuses on the battery pack are still intact.

Is it likely to have damaged any other components? If it's worth it I'll just replace the chip, but I don't want to do that without knowing the cause first.

Thanks guys.

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[V-bro]

Usually a little chip of metal (copper wire stripping remains or some from enclosure drilling, or a tiny chip of a bolt) causes this as it makes its way to short some SMD parts.....Pretty common in a portable device...

[MickB]

Is it likely to have taken out any other components? Or is it just a matter of soldering in a new chip and seeing if it works?

The 41Hz shop is out of stock of the TP2050 IC at the moment but there are some TP2050 and STA505 ICs on eBay. Do I have to be careful of dodgy or counterfeit ICs, or is it reasonably safe buying them like that? Farnell have an STA505 but it has no heat slug and it's only rated at 50W (or 80W depending which bit you read).

[krilli]

I've nuked the STA505 chips with nothing else being gone.

I'd consider taking an STA516B, it's probably going to be more robust in some ways, can drive lower impedance and use higher voltages:
Mouser: http://eu.mouser.com/ProductDetail/S...LVwzveHg%3d%3d
Digi-key: http://www.digikey.com/product-searc...yWords=sta516B

STA510A is nice too. Power capacity between 505 and 516, plus it has a quite low RdsON, which I believe translates into slightly higher efficiency (not sure though ...?).

[MickB]

Thanks Krilli. I'll probably go for the STA516B as Farnell have it in stock and I've got to order some other stuff anyway. Robust is good! I take it there are no disadvantages compared with the STA505 - other than costing a little bit more that is.

BTW, the STA505 Farnell stock does have a heat slug, it's just that the picture on the product details page shows a generic IC.

[krilli]

Yup. Don't know if it's worth much, but I'd like to confirm: AFAIK the STA516B is only better and more expensive. And I've seen that "wrong pic of STAxxx chip" thing somewhere else too

[MickB]

I've removed the old chip and the package is cracked all the way across underneath, surprising how much energy is released when something like this happens. Need to think of a way of keeping any crap off the circuit board now. It had crossed my mind that it might be a problem if a nut came unscrewed and rattled around inside so I used Nylocs on everything, but I hadn't thought about small pieces of metal debris causing a short.

[V-bro]

I expect it is just the STA, but it's never too late to get another TC2001 after you've tried. I render it highly unlikely for a defective TC2001 to take out the STA chip, so no worries expected there....

When you connect it is there 5V? Usually when the TC goes the 5V section is shorting more or less and pulls down the 5V. Take care to measure this on the designated jumper and crank it only briefly, if it's there it's there.... (shorted 5V inputs on the TC might on the long run make the regulators run hot...)

[MickB]

Thanks V-bro. Looking good - I've just checked the 5V supply and it's 5.04V with the isolating jumper off and the same with it on.

[V-bro]

Then I expect it to work again just fine with a new power stage chip!

You could as a double check measure if none of the brown little ceramic caps are shorted, and the outputs towards the speaker outputs... If these are measuring fine high-ish resistances and the outputs measure equal resistances then that's fine too...just to be sure...