[sdiy] P5

[Harry Bissell Jr]

Hi Tony

I just put a bigger heatsink on my P5 and had no
problems with heat. I got the idea from Santana's
keyboard player, who had an outrageous sized heatsink.
OTOH its much hotter on stage.

I used a slice of heatsink extrusion with continuous
fins across the whole heatsink area, about 1"
extending
out the back of the P5.  It was easy to do and took
about an hour. Never ran warm after that.

H^) harry


Hi all,

Has anyone tried upgrading the Prophet Five's power
supply? I have one
and it needs a new transformer because the present one
hums audibly. 
Its
a simple power supply design in the rev 3.2 and 3.3.
But the problem is
that it is too simple.

Firstly there are no protection diodes around any of
the three terminal
regulators. This is easily rectified [ :-) ] by adding
the missing
diodes. Secondly the rear heatsink gets really really
hot. OK, its not
quite as hot as JP-8, but its hot enough to get me
worried.

The +5V rail is a 7805 with a diode on its GND leg
taking the output to
5.6V. This regulator takes its feed from the 26V
unregulated voltage 
that
also feeds the +15V regulator. Now dropping nearly 21V
at around 800mA 
is
sure going to cook the little fella and the heatsink
gets rather warm.

It seems to be asking for a separate low voltage feed
from another
smaller transformer for this regulator alone. Anyone
done this, and did
you have any problems with the u-proc reset line that
takes its signal
from the raw 26V supply?

Alternatively, I was thinking of a pre-regulator
design for the 7805. 
Or
possibly even a switch mode [shudder..] unit to
replace the whole lot.

I'm cross posting this to AH and Synth-DIY so please
watch your 
replies.

Many thanks,

Tony

www.oakleysound.com