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Old 16th November 2010, 01:24 PM   #621
udailey is offline udailey  United States
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Linuxguru gave you great advice. From watching other people have similar problems I am betting you have issues with LM318. Hopefully thats all. Do you know how to check if LM3886 is in contact with sink? Put DMM on the tab of LM3886 and also on the heatsink. If you have any resistance at all this is a bad thing. 0 resistance is obviously very bad. We are looking for no reading. Just using the mica sheet is not good enough. You must use a shoulder washer as well because the bolt will touch the tab and short it to the heatsink without the shoulder washer.
Uriah

PS HEY LINUXGURU do you still have more boards? I have had a few requests for boards and want to know if I can send people to you.
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Old 16th November 2010, 03:13 PM   #622
ra7 is offline ra7  United States
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Thanks for the tips guys! I'll check it out when I get back from work today.

Yes, I mounted it without isolation to the heatsink as it is in test mode. But, now I've dismounted it. The LM3886 tab has the full -V as it should. I'll check the 318 voltages.
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Old 16th November 2010, 03:33 PM   #623
udailey is offline udailey  United States
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So, its okay usually in test mode to have no isolation to heatsink. Problem comes when heatsink touches just about anything else. If it comes in contact with ground for split second she is burnt. So keep that sink on cardboard and also you may want to try to insert some insulation between board and sink so that they can not touch as this might make a resistor leg or blob of solder or simply copper on side of board touch sink.
Swap your LM318 for the one from the other channel if both channels have not had problems.
Uriah
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Old 16th November 2010, 04:41 PM   #624
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Quote:
Originally Posted by udailey View Post
PS HEY LINUXGURU do you still have more boards? I have had a few requests for boards and want to know if I can send people to you.
Yup, some 30+ version 1.3 bare boards left, both Chinese and locally-made ones. You're welcome to refer interested people here - I can always source more boards with about 2-4 weeks lead time if there's sufficient interest.
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Old 17th November 2010, 01:47 AM   #625
ra7 is offline ra7  United States
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Quote:
Originally Posted by udailey View Post
Swap your LM318 for the one from the other channel if both channels have not had problems.
Uriah
Yup, this worked... the led glows, relay clicks and the dc offset is about 8mV. So, that means the LM318 is gone. I haven't played music through it, but I'm sure the rest is ok.

I checked digikey and mouser, niether have LM318.

Anybody know of a quick source for these?

Thanks for the help guys!
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Old 17th November 2010, 01:56 AM   #626
udailey is offline udailey  United States
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Glad it worked. Seems like a lot of those things didnt work in the circuit.
Try ArrowNAC. They have everything. Avenet and futurelectronics to are good places for IC's if Mouser and Digikey dont work.
OCTOPART.com is a good place to start when you are looking for a part.
Uriah
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Old 17th November 2010, 02:18 AM   #627
ra7 is offline ra7  United States
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Cool website! Thanks Uriah!
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Old 17th November 2010, 08:46 AM   #628
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Quote:
Originally Posted by ra7 View Post
Yup, this worked... the led glows, relay clicks and the dc offset is about 8mV. So, that means the LM318 is gone. I haven't played music through it, but I'm sure the rest is ok.
...
Anybody know of a quick source for these?
Funky - sorry about the dead LM318N. This is the first I've supplied that has died, but it does happen on occasion. Before looking for a new one, clean out its leads with a razorblade and test it again - it may just be oxidized leads.

I think you'll be happier with a TI LM318P, although it has a different sonic signature. Check at Radio Shack and Frys (if there's one at Seattle), otherwise get it from EBay, preferably from a US seller - it should run about $1 in volume, maybe a few dollars in pairs.

Edit: Maybe the X-Ray screening at Mumbai Airport for overseas cargo isn't friendly for sensitive semiconductors like opamps, etc. - just a guess. I'll know for sure if there are more failures like these in the kits shipped to the US.

Last edited by linuxguru; 17th November 2010 at 08:52 AM. Reason: addendum
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Old 17th November 2010, 01:06 PM   #629
udailey is offline udailey  United States
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Probably wont be the last one. I had a lot of dead ones but never knew it til people started building. They arent dead they just arent working in the circuit.
Uriah
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Old 17th November 2010, 02:04 PM   #630
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Originally Posted by linuxguru View Post
I think you'll be happier with a TI LM318P, although it has a different sonic signature.
I tried to seach but could not find useful info, can you elaborate on what you mean?
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