x0x troubleshooting - audio out?

Re: x0x troubleshooting - audio out?

Postby guest » Sat Jan 10, 2015 7:01 pm

what that means, is that Q17 is off, and therefore its Q28 that is leaking the current into C33, which is not good. the C33/D25 measurement test i posted earlier would confirm this, as its possible that the act of measuring D25 shuts off Q17.
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Re: x0x troubleshooting - audio out?

Postby far gon » Sat Jan 10, 2015 7:19 pm

Alright just tested that.

C33 stayed at 9.2v on the scope, while the largest reading I got from D25 that time is 373 mV (measured simultaneously.

So do you think replacing Q28 will probably solve the issue? Could this leaking current have compromised other components?

Also, could you tell me what Q28 is or a part # or something? I figure its worth a shot to try to replace. I would kind of feel bad just tossing the x0x-heart... but maybe its cheaper and easier than trying to replace Q28.

Again, I REALLY appreciate you helping me through this!
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Re: x0x troubleshooting - audio out?

Postby far gon » Sat Jan 10, 2015 7:37 pm

Well suppose i should have looked in the most obvious of places, the x0x wiki, to find the parts list pdf for the x0x-heart. I not completely helpless lol!

So I found the replacement part for Q28:

http://www.mouser.com/ProductDetail/ON- ... jFNw%3D%3D

and will tack it on to my next mouser order.

Is there anything else you can think of to get 'just in case' to replace (or test further)?

Thanks for taking the time to help me. In the great spirit of DIY, I will do the same for another in need if I can help. Just keep me away from probing your x0xen ;P
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Re: x0x troubleshooting - audio out?

Postby guest » Sat Jan 10, 2015 7:38 pm

you can try removing Q28, and then testing C33 again. if you get an oscillation, then Q28 was the culprit. the part number 2SK3666-2. removing small parts like that can be difficult, the issue is that you need to heat all 3 pins up to melt the solder simultaneously, and then use a pair of tweezers to lift it off the board. there are a couple of ways of doing this. if you have a hot air pencil, or heat gun with really small nozzle, you can locally heat the part and lift it off. you can also use a soldering iron, and apply flux over the part, and then quickly go from pin to pin, trying to spread the heat evenly, and then lift it off. the final method is to heat a pin, lift it up with a pair of tweezers, and then do the other pins. you have to pry a fair bit to get the pin to bend up, though.

another method for testing, would be to just cut the trace that goes to Q28 from C33. you could make a solder jumper if Q28 wasnt the problem.
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Re: x0x troubleshooting - audio out?

Postby guest » Sat Jan 10, 2015 7:39 pm

oh, another method for getting SMT parts up is to use solder wick and get as much solder up as possible, then lift the part off.

its probably worth taking Q28 off first before placing the order, to see if it is really the problem. let me know how it goes.
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Re: x0x troubleshooting - audio out?

Postby far gon » Sat Jan 10, 2015 7:57 pm

Good point on making sure I can successfully remove the part before ordering a new one, and to see if it was in fact the culprit. Thanks for the removal tips, this will be interesting. A new challenge!

I will post here as soon as i find out.

Im also tempted to solder on the headers of one of my other untouched xox-hearts and mate it with this pacemaker to get one working, rather than building another up from scratch.

Do you think this is wise?

Im doubting the fault has anything to do with the pacemaker, and am more convinced I shorted J6 pin 1 to pin 2 (gnd) to cause this damage. But my wisdom also told me to start tuning this thing at 3am without a break from building it, which in hindsight was not a good idea...

Patience Grasshopper or acid chirps of success?
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Re: x0x troubleshooting - audio out?

Postby guest » Sat Jan 10, 2015 8:13 pm

measure the resistance to ground from the various pins on j6 to make sure there isnt a short on the pacemeker, and if it all seems good, then put a new x0x-heart on.
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Re: x0x troubleshooting - audio out?

Postby far gon » Sat Jan 10, 2015 8:17 pm

Q28 removal is a success!

...and probing C33 to ground produces a saw wave!

It is biased to only positive voltage, but the pacemaker AC-couples the signal, correct?

So it was Q28 after all.

Well I feel a lot better knowing im close to a working module, once i can solder in that tiny little replacement Q28 anyway.

Anything else I should check?

This was a learning experience for sure!

I know I've said it enough times to probably annoy you by now, but here it is again: THANK YOU GUEST!!!
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Re: x0x troubleshooting - audio out?

Postby guest » Sat Jan 10, 2015 8:25 pm

wow, awesome news! and congrats on getting that sucker off, that was the difficult part. putting a new one back on will be much easier. which method did you use to remove it?
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Re: x0x troubleshooting - audio out?

Postby far gon » Sat Jan 10, 2015 8:41 pm

I used the method of putting a small sharp flat blade screw driver under the edge of the chip, and then heating the nearest pin while applying a turning/prying force. The last pin ended up snapping, but its easy enough to apply a little more heat with a tweezers to get the remaining pin metal.

Yea it sure makes it fun when you have to fight for victory... I mean who wants to just have successful builds all the time?!
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