Vintage Synth Repair

Thanks a lot !

> >Also, does this indicate that some other board shorts the -15v 
rail ?
> 
> not really, no

What I mean is, does the tantalum cap get fried because there is a 
short between the -15v and ground caused at one of the boards, or the 
only possible reason is high secondary transformer voltages which 
overheat the 7915 regulator ?

How do I check the secondary voltages and what should I see there ?...

Thanks again for the help !!!




--- In vintagesynthrepair@yahoogroups.com, "Scott Nordlund" 
<gsn10@...> wrote:
>
> >News - I replaced the tantalum cap with one that can handle up to 
25v
> >and disconnected the other boards from the synth, the cap has not 
got
> >fried at all, but voltages are inaccurate-
> 
> This doesn't necessarily mean the problem is entirely fixed unless 
you 
> verify that the transformer secondary voltages are okay.  If 
they're putting 
> out more than they should, you may overheat a regulator once a load 
is 
> connected.
> 
> 
> >-15v read -14.6
> >+5v  read +4.25
> >
> >the +15v and -5v are adjustable so they're ok...
> >
> >What could cause the inaccurate voltages ? should I replace the 
7915
> >and 7805 ? or maybe some particular caps ? or do they appear like
> >this because no board is connected to the PS ?
> 
> These regulators should work regardless of load.  If the input 
voltages are 
> okay then you may want to replace them.
> 
> >Also, does this indicate that some other board shorts the -15v 
rail ?
> 
> not really, no
> 
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