[sdiy] puff of smoke! (MB-808 build)

[Danjel van Tijn]

thanks I looked at the traces carefully and tested continuity but
nothing seems to be wrong. Next step is pulling the TL074 out and
measuring the voltages at all the pins.

After that I am pretty much going to have to rebuild the whole circuit
(except for the resistors) if I can't isolate the bad cap/tranny


On Fri, Jun 26, 2009 at 4:44 PM, Kevin<kevingeo at gmail.com> wrote:
> Did you look carefully on the traces of the board?  Sometimes traces
> may be damaged.
>
> On Fri, Jun 26, 2009 at 2:11 PM, Danjel van Tijn<danjel at gmail.com> wrote:
>> So just finished building an MB-808 clone. I have gone through and
>> tested each section and everything works except for one problem:
>> At one point I put in the ICs and pots to test the HT section. When I
>> applied power I saw smoke! I inspected the ICs and it looks like the
>> TL074 had a crack midway through it. I am not sure if this crack was
>> there before (but didn't see it) or it was a result of some other
>> problem.
>> After replacing the IC there was no more smoke or shorts but that
>> section of the circuit is simply not working. I have looked at a lot
>> of the suggested test points and I am only getting sound at one point
>> (marked in red):
>> http://eight-oh-eight.org/phpbb2/viewtopic.php?t=141
>>
>> I can't hear anything from the noise source and nothing from the opamp.
>>
>> The circuit it actually fairly simple if you look at the schematic.
>>
>> Any tips for fixing this? I am wondering what could have been damaged....
>>
>> thanks,
>>
>> Danjel
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>