[sdiy] Korg SDD-3000 5 volt supply problems

Steve Lenham steve at bendentech.co.uk
Sat Nov 17 15:05:35 CET 2018


On 17/11/2018 12:47, Gordonjcp wrote:
> On Fri, Nov 16, 2018 at 08:31:14PM +1000, Adam Inglis wrote:
> 
>> But, once I reconnect the transformer winding to the 5 volt supply, it glitches as before, intermittently.
> 
> Okay, so that eliminates the transformer, the diode bridge and the
> smoothing cap, and possibly the loading of the bench PSU would affect
> any runaway oscillation in the 7805.  
I'm not sure that is correct.

As I read it, Adam says that feeding the input of the 7805 with DC from 
his bench power supply results in flawless operation with no glitches, 
but that if he reconnects the transformer and powers it from mains, the 
glitching returns.

This seems to point the finger at either the transformer, bridge 
rectifier or smoothing cap (including associated solder joints), not 
exonerate them.

Adam, is that right?

Cheers,

Steve L.






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