[sdiy] can a PSU destroy voices chips?

[Antonio Tuzzi]

pretty scary! 
I don't want to to think to a similar CATASTROPHIC failure in a MM ...  (or an OB8)

at

On 18/nov/2013, at 17:33, Paul Schreiber <synth1 at airmail.net> wrote:

> Yes, this is normal.
> 
> Paul S>
> 
> 
> --- antoniotuzzi at gmail.com wrote:
> 
> From: Antonio Tuzzi <antoniotuzzi at gmail.com>
> To: Synth DIY <synth-diy at dropmix.xs4all.nl>
> Subject: [sdiy] can a PSU destroy voices chips?
> Date: Mon, 18 Nov 2013 17:24:39 +0100
> 
> Hello friends
> 
> after more than 3 years I decided to repair the ProOne... 
> 
> was working, but one day decided to stay mute
> 
> situation was this:
> 
> -15v ok
> - 5 ok
> + 5 -> 4.3
> +15 -> at startup was around 12 going down to zero in 5 seconds
> 
> 
> after changing the regulators (no success)
> changed all the caps in the regulators area and more (and the 2 bigs)
> I tested the PSU with no load (it's a an DP 241 5 36, dual V 220 and 110)  (only 0.35 A, seems very LOW!!!)
> and on the secondary I had 20,7 and 20,7 
> 
> but I decided to test with another PSU, at this point, the positive regulators were giving correct Voltages +5 and +15
> 
> but all the cem3340 were silent, no sign of oscillations on the oscilloscope
> 
> All DEAD! 
> 
> This is the first time I've seen so many 3340 dead at the same time :((((
> 
> I had 3 new 3340 and the pro one is working ( I discovered a DEAD 3310 too... filter ADSR)
> 
> Question
> Is it (A)normal that a bunch a CEM are dead for a failing positive rails ?
> 
> 
> Thanks
> Antonio
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