[sdiy] Korg SDD-3000 5 volt supply problems

Gordonjcp gordonjcp at gjcp.net
Wed Nov 14 09:26:39 CET 2018


On Wed, Nov 14, 2018 at 06:52:26AM +0000, Oakley Sound wrote:
> The first thing I would do is measure the current that the 7805 is
> supplying to the digital board. However, this may mean you have to
> break the wire carrying the +5V to that board. There is a
> possibility that the digital board is taking too much current and
> causing the 7805 to go into current limit. This would suggest a
> fault on the digital board somewhere - a decoupling capacitor is the
> most likely culprit.
> 

I've changed more 0.1μF disc ceramics (or SMD ceramics) than I've ever
changed electrolytics.

> That said, it may be the 7805 itself that has gone faulty so it may
> be just easier to replace the 7805 in the first instance.

Unusual, but it fits the symptoms.  If one of the 7805's decoupling
capacitors has gone leaky, it's probably now a fairly effective VHF
transmitter and that'll cause weird effects.

-- 
Gordonjcp




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