[sdiy] Prophet 5 -15v rail is shorting... Need advice

[ASSI]

On Freitag 09 November 2007, Gil W. wrote:
> What I got is even lower +15v voltages. This one has
> dropped the voltage to below 14v !! So can we conclude
> from this experiment that simply the P6 transformer
> cannot handle the Prophet's load ?

Again, if the specifications you gave are correct, that's implausible.  
However if you want to be sure, you can put both transformers in 
parallel (and in phase of course) at least as an experient and see if 
this improves things.  If it does it still does not mean that the 
transformer is inadequate, but at least it would point to a problem 
before the regulators.

> Btw, the voltages going to the regulators with this
> (the second) transformer, are:
> +21.20v
> -23v

>From the schematics this sounds about right (assuming that is an RMS 
value) and the regulators should have no problem with the headroom - if 
the filter capacitors in front of the regulators are correctly 
dimensioned.  Can you check the ripple on the regulator inputs?


Achim.
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