[sdiy] Wiard/Blacet Miniwave issue - Help please

[Thomas White]

Just gave a warm chip test. PS1 on the positive rail does get hot. No IC's get hot. When I wiggle the poly fuse on the positive rail operation goes normal then when I let it go the power drift down starts again. No time to solder as I have to go to work. Maybe a cold solder joint? I am thrown off by the wiggle solving things temporarily. 

Thomas White
Natural Rhythm Music
www.naturalrhythmmusic.com

> On Mar 31, 2016, at 8:10 AM, blacet at blacet.com wrote:
> 
> Check the 5v supply also!
> 
>> Just a friendly reminder: Any time you have even the slightest suspicion
>> that there might be a power issue with your electronics, always put on eye
>> protection before powering up the device. You don't want capacitors
>> exploding and damaging your eye!
>> 
>> Ok, now, back to your regularly scheduled circuit diagnostics...
>> 
>> Brian
>> 
>> 
>>> On Mar 30, 2016, at 8:55 PM, m brandenberg <mcbinc at panix.com> wrote:
>>>> On Wed, 30 Mar 2016, Thomas White wrote:
>>>> My Wiard/Blacet Miniwave is doing something strange now. It is a Rev.0
>>>> board. When I power it on, all is well. 30-40 seconds into power on the
>>>> right most LED's fade to off. Then the rest start fading and "dancing"
>>>> a bit before all of them turn off. The longer the power is on, the fade
>>>> out to non-functioning gets faster. Does anyone know what causes this?
>>>> When looking at the power rails, my supply is solid. The power
>>>> component PS1 (unique to my Blacet modules), right after the power
>>>> jack, loses voltage the longer the unit is on. Think it is shorting the
>>>> voltage to ground? Seems like my likely issue is to replace this part.
>>>> Thoughts?
>>> 
>>> "Loses voltage"...  measured between where and where?  The
>>> PS devices are polyfuses, they are near shorts when functioning
>>> and open up under increased current.  So there should be
>>> near zero volts across one when all is well, rising when
>>> there is a problem.  The usual circuit follows the PS with
>>> a diode to ground so that if you reverse the power supply
>>> voltages, the fuses open up quickly saving everything.
>>> 
>>> If you are seeing this (voltage across the fuse increasing)
>>> and the nearby diode is cool, you could have a bad fuse.  But
>>> the slow path to failure smells like passives more than
>>> actives.  Poke around looking for a hot component.  And
>>> give the electrolytics a very good eyeball.
>>> 
>>> To test the fuse, swap it with the other and see if the
>>> problem moves to the other rail.
>> 
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at dropmix.xs4all.nl
>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
> 
> 
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy