[sdiy] Korg SDD-3000 5 volt supply problems

[Adam Inglis]

> On 16 Nov 2018, at 5:46 PM, Gordonjcp <gordonjcp at gjcp.net> wrote:
> 
> That's not right.  7805, TO220 package?  That shouldn't even be close to
> shutting down at 700mA, unless you mean that the bench PSU is giving up
> before the 7805?


Gordonjcp, well spotted, absolutely right - I had this new bench supply machine incorrectly set up. Now, (after removing the 700 mA "over-current protection” limit on the unit, oops!  :::rolls eyes:::)  and running the PSU 5 volt line from that supply with various loads, I can’t reproduce the glitch at all. 

But, once I reconnect the transformer winding to the 5 volt supply, it glitches as before, intermittently. 

With the SDD-3000 hooked up to the bench supply, I plugged in a signal generator and calibrated it as per the service manual. Perfect. And no glitches over a couple of hours.

I’m wondering, can transformer windings fail like this, intermittently, under load?