Voltage Regulator question

[KA4HJH]

>Is this an okay adaptor to use full time on this piece?  Is 9V too much
>to feed a 7805?  I don't believe so, but I could be wrong.

The 7805 needs at least 8V to work properly. The actual voltage from 
your adaptor will depend on the load imposed by the circuit so the 9V 
rating is only a ballpark figure. Measure the voltage across the 
filter caps while the device is on (careful with those probes). Also 
make sure it's not too high for the caps ( >90% of the rated voltage 
is too high). How hot does the regulator get? If you can keep your 
finger on it for more than five seconds you're probably safe.

Another possibility is that the adaptor is itself being overloaded, 
not enough to prevent the device from working but enough to cause 
distortion, hum, etc., but you'll hear that--assuming this is an 
audio gadget.


I have a KORG pedalboard that worked fine with one adaptor, but blew 
a transistor in the PS with another slightly higher rated one. Mind 
you I think there may be an excessively high load on that little 
transistor, because it gets WARM.


-- 
Terry Bowman, KA4HJH
"The Mac Doctor"