AMP6B troubleshooting / newbie arrival.

[Jungle-ras]

Hi guys.
Newbie here, been browsing the forum for quite some time and went to order my first DIY-amps some two weeks ago. Because of all the positive feedback on the AMP6 and my project being a Festival-Boombox, i decided to go for that one.
Been some years at Roskilde Festival with the same DIY boombox, sporting many different amp-setups, since the amps tends to get stolen every single year (poor concealing of the box i guess). I´ve ran a T-amp before, some chinese TA2020 pre-assembled product, that my friend got of eBay and we were very satisfied with it. Especially the battery life you get from it. Of course, that one got nicked to. This year i will, as mentioned, go with the AMP6B for the box. Ordered 3(!), one for myself, one for my girlfriends box and one spare. Have assembled two of them as of now, and im having some trouble with both.

So here goes the troubleshooting.
Soldered the first one extremly thorough in accordance with the assembly info given on 41hz.com. At first I got the rapid clicking noise, redid some solders and i eventuelly, without to much hazzle, got music from the speaker. After a track or two, the amp would go back to rapid clicking and the chip became very hot (to hot to touch). After a few minutes the amp would play again. I hooked it up to my boombox (2 x 2 p.audio 8ohms in parallel with 2 x 2 piezos paralleled as well. Ill upload the schematics if that would be any help to you guys) went outside and played for some time with the amp getting only moderatly hot, maybe because of better circulation outside. No problems there.
Some days later as i powered up, the amp was back to rapid clicking. I started troubleshootin earlier today and now it doesnt even click. There is no outpu to the speakers whatsoever.

The chip still gets hot
Ive got approx 5V over C2
approx 1.2V over R7
only have about 100 - 120 mV over C5 (should be around 10V)
I run a 12V 60Ah car battery as power supply, somewhat new and recently charged
low output on J10

I have some knowlede in schematics and datasheets, and used these a bit in troubleshooting, and as far as i can see, my the only "wrong" is the voltage over C5.
Heres some pictures of the pcb
DSC_0644.jpg
DSC_0646.jpg
EDIT: Pictures in full resolution:
Picture 1
Picture 2


I apologize for the long description, I hope you guys will share some of your wisdom in what my next move is. Any help would be greatly appreciated.
Im sure i missed some important in my description. Please let me know if you need more info to tell what is wrong.

[tuo]

Your pictures could be bigger in size. But some comments:

- Picture 1: You could clean the board. At least on the bottom side there's lot of residue around the corner with C50, which may be a reason for problems that come and go.

- Picture 2: Gaah! That green/yellow wire should be used for grounding only, nothing else. Your power wire connections looks a bit suspicious too, with that long wire coming out of the PCB and some strings hanging out of the wire there's a possibility of short circuit.

With your symptoms I'd also check the C16 and soldering on the chip with pins 27, 29, 31 and 32.

[Jungle-ras]

1. That makes perfectly good sense. What is a good way to clean them? I tried with scratching it loose and carefully blowing afterwards with compressed air.

2. For that i am sorry. I ran out of black wire, and im aware of the obvious suspiciousness. But thanks for pointing it out, Ill correct it the first thing in the morning.

And thank you many, this is exactly the kind of pointers i need.
Here´s the images in full resolution, i´ll add them to original post as well

[tuo]

There are couple efficient ways to clean the board:
- with 99% Isopropyl Alcohol
- with a special cleaning spray made by Kontakt, see here.

About the clicking see this too: http://www.41hz.com/forums/content.p...roubleshooting

[Jungle-ras]

Really nice link you gave me there, i might actually have picked up a thing or two on there that i did not know. Thanks alot. I´ll get myself some isopropyl tomorrow.
I really appreciate your help so far. I´ll report back in tomorrow (or later today, that is)

Edit: Oh and the troubleshooting link, i´ve seen that one before. Don´t mention much about the clicking, but ill go through it just one more time. Thanks again

[Jungle-ras]

Hi again
Sorry for the delay, i didn´t consider that most shops in Denmark are closed on sundays, so I had to wait for monday to get some isoprop.
I cleaned of the pcb carefully with the toothbrush method (Let me now if that was a bad move) and redid some weak solders but still the same. Although i did have a slightly higher voltager over one side of J10, maybe 250 mV as i recall, but not enough to run an LED or suspect logic high, but maybe im wrong here.
Also checked that my fuse was still intact, and redid those awful 12V wires (Didn´t have black, so blue will have to do)

So to summarize, still no output. Chip still gets mildly hot, though. Voltage over C2 is still around 100 mV.
Am I in any possition to consider I got one of those damaged chips mentioned on front page, or did i just do something wrong along the way? I don´t reckon i shorted any pins in my troubleshooting, but since the amp once played and now dont, I´m starting to think I´ve somehow damaged the chip.

More pictures, maybe with a bit higher aperture this time, can be provided if needed.
Thanks in advance

[tuo]

From the troubleshooting link:

Repeated clicking sound (AMP-6x, others)
When J2-jumpers (mute/awake) are in place

* Something on the output section is short circuited and the amp protection mutes and tries to restart about once per second.
* Check+Clean all soldering on the output section, so there is no short circuit
* Check to see if the speaker cables are not shorted

Unfortunately I have a vague feeling that I have read that this clicking sound will not last forever. The chip heats up and finally destroys itself. Ah, found it, see here: http://www.41hz.com/forums/showthrea...0121#post30121 So there's a possibility that the chip is now dead since the clicking is gone.

[Jungle-ras]

Hmm, bummer. I give it another go later. Will try going over the datasheet and schemtaics and se if i can spot the problem. Thanks for the heads up anyway

[alexlangberg]

Have you seen this? I'm not sure this is your problem but it could look like you have the silver colored legs like the chips from China?

[Jungle-ras]

Have you seen this? I'm not sure this is your problem but it could look like you have the silver colored legs like the chips from China?

It is most certainly those chips I got. But so far, my problem hasn't been a weak channel. But i guess it could be a faulty chip. Thanks for the heads up, i'll look into it.