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Dr. Bob
Moderator
Australia
6593 Posts |
 Posted - 04/29/2007 : 12:03:38
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quote:
Originally posted by Dirk
Some of the older pedals (ACA powered) won't run on 9 volts regulated (PSA).
If you measure the voltage from an ACA adapter you'll measure 12 volts instead.
The trick is to replace the voltage regulator with a 12 volts type (7812) and it works just fine. 
Hi Dirk & Guys
Good point about the 7812 Dirk.
But then you would have to be extra carefully not to use the 12V supply on the newer 9V PSA type pedals.
Easy to forget, when your on a dark stage in the middle of a gig.
I have modified all my PSA pedals to run on 9V.
It's just a matter of linking out the low value resistor, that's in series with the diode on the DC input.
This resistor is usually around 220 to 330 ohms.
i know some people also put a link on the diode, as it drops 0.6V across it, but i like to leave it in circuit, just in case.
Or you can always just use it this way:
Powering ACA pedals with a PSA power supply
Powering the older pedals designed for 12V DC input with either a newer ACA or PSA adapter will not work very well. The voltage drop over the resistor and diode will prevent the pedal from getting enough power and its LED will usually only glow faintly. The solution is to use a daisy chain and plug in another pedal designed for the newer ACA or PSA adapter. The lead between the two pedals will short the resistor diode pair and the pedal will receive full power.
But I guess you then have the reverse situation, of being careful not to use it on a 12V PSA adapter.
I put a sticker on all my ACA 12V modded to PSA 9V pedals.
saying "PSA 9V only".
Or you could wire in two regulators, a 7809 & a 7812, and label the output leads or connections.
Regards Dr. Bob
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Regulated vs Unregulated Power Adapters
