Vintage Synth Repair

All right and thanks for your message(s)!

You don't have to use a scope to test for AC leakage. A multimeter can do the job. Set it to AC voltage test and probe the DC output tabs of the rectifier bridge. If you get a significant reading, then you know that the bridge is toasted.

I think it make sense for a PSU this age (and with an obvious problem) to replace all passive components at first such as electrolytics which are essential for stability (all of them, starting with the big regulating ones), and test others like you did for resistors, as an example. Once you're sure about the reliability of your passives, you can tackle your actives (transistors, IC, etc...)


--- In vintagesynthrepair@yahoogroups.com, eidorian@... wrote:
>
> I'm sorry, not at all!  I just haven't been able to get to my venerable 
> old Tektronics CRO, which is buried at the rear of my shed behind an 
> enormous pile of junk that is too unstable to climb over :-(
> 
> Your advice is excellent; my failure to follow it is the only thing 
> lacking.  Please accept my apology, I appreciate your help.
> 
> Cheers,
> A.
> 
> 
> On 2013-08-01 08:20, cpt.zilog wrote:
> > Excuse me but I'd like to know if I did say something false or stupid
> > in my previous message ?
> >  Don't want to sound rude, but if my idea is wrong, my ego can handle
> > it as long as someone corrects me (and write it!) ;)
> >  Thanks
> >
> >  >
> >  > --- In vintagesynthrepair@yahoogroups.com, "cpt.zilog" 
> > <cpt.zilog@> wrote:
> >  > >
> >  > > Hello guys and sorry to jump in like that but I would suggest to
> > change the big caps as a priority and then check the bridge rectifier
> > again for leakage of AC current.
> >  > >
> >  > > I had a big problem with a D&R console's psu in which the
> > voltage regulators kept on going Kapput. Turned out that the big
> > Electrolytics were bad and that induced a big stress on the rectifier
> > bridge, which in turn had the consequence of not only letting DC pass
> > as expected, but also AC at the same time !
> >  > >
> >  > > I did test for AC leakage on the rectifier after the newly
> > installed voltage regulator worked for a couple of seconds before
> > shorting...
> >  > >
> >  > > After new BIG caps, new bridge rectifier and a 2nd new voltage
> > regulator, everything was sorted.
> >  > >
> >  > > Good luck !
> >  > >
> >  >
>