DC Power Supply for SRD Rockman

[jsharpe@bigpond.net.au]

Hi,
I'm new to this site, but I'm hoping someone out there can tell me if it's possible to build a -6V/0/+6V power supply to drive my old Rockman which is a battery-only model... At first I assumed a 12V supply would do the trick but when I opened the Rockman up I discovered that ground/earth was connected to the middle of the 8 AA cells inserted into the unit - 6 volts a side! I've contacted Dunlop but they don't seem to have a very elegant solution. Any ideas?

[Steve Conner]

Hi,

You could try a 12V supply from a regulated wall wart, with a voltage divider made of two equal valued resistors (let's say 1k) to the mid-point. Use a capacitor (say a 22uF electrolytic) across each resistor to bypass it at AC.

This should work fine because the mid-point should draw hardly any current, otherwise one half of the batteries would wear out before the other half, which is bad design, and Tom Scholtz wouldn't have done that because he looks like a pretty smart guy I've seen Marshall stomp boxes "convert" their 9V battery to +/- 4.5V this way.

[cjlectronics]

You could build a circuit from the MAX1044 charge pump circuit. Check this link out http://aronnelson.com/gallery/TheBigMan-Layouts and open the Invertor/Bipolar Supply from Charge Pump diagram. It is a simple circuit to build and you could use a 6 volt wall wart along with this circuit to produce the +/- 6vdc supply. I would recommend using a regulated 6 volt wall wart though.

Good luck,
CJL

[Odd I/O]

Hi,
I'm new to this site, but I'm hoping someone out there can tell me if it's possible to build a -6V/0/+6V power supply to drive my old Rockman which is a battery-only model... At first I assumed a 12V supply would do the trick but when I opened the Rockman up I discovered that ground/earth was connected to the middle of the 8 AA cells inserted into the unit - 6 volts a side! I've contacted Dunlop but they don't seem to have a very elegant solution. Any ideas?

Rockman Made a power supply for this model that consists of a wall-wart that then connected to a module that plugs into the empty cavity where the batteries normally go.
It's called the "Rockadaptor"
Trying to fabricate one yourself might result in a lot of headaches involving 60 hz hum. You might find one on ebay for pretty cheap.
Even If you end up having to pay 30 or 40 bux for it, it's still not bad considering how quickly 30 or 40 bux of batteries can be depleted.

an auction recently ended on ebay that had both the rockman and the power supply and THE PAIR went for only 93.00 It has a picture of the unit with its power supply just so you can see what it looks like:
http://cgi.ebay.com/Rockman-X100-by-...QQcmdZViewItem

[stublito]

Hi,
I'm new to this site, but I'm hoping someone out there can tell me if it's possible to build a -6V/0/+6V power supply to drive my old Rockman which is a battery-only model... At first I assumed a 12V supply would do the trick but when I opened the Rockman up I discovered that ground/earth was connected to the middle of the 8 AA cells inserted into the unit - 6 volts a side! I've contacted Dunlop but they don't seem to have a very elegant solution. Any ideas?

The Rockadapter uses 9VAC to a diode bridge to get about 16VDC which then goes to a 12V regulator. Then it uses a 5.6 V 400 mw zener diode and a 220 ohm 1/2 watt resister in series across the 12 V. The junction of the zener diode and the resistor is used as the 0 V refernce for the op amps.

Stublito

[oc disorder]

Ages ago I made one for a friend.
Got one of those selectable wall warts (plug packs) was something like 3v to 16v but it had some secondary tappings so i was able to seperate the windings to get approx 6 volts x 2 .
This was for one of the early Rockmans. I made an identical back panel
(the bit of plastic that holds the batteries in and forces them on to the internal springs/batt contacts) from a scrap of pcb .
I used 4 brass boltsthe length of a battery (2 for 0 volts and to help hold it square) and those chrome nuts (forget the name dome ?) that are enclosed normally used to be used for holding mirrors on hotel restroom walls, with plastic tubing covering the bolts. So the end result was a ugly looking plug that fitted into the battery cavity. The chrome dome nuts pressed on the battery springs which connected the power supply to the Rockman.
If need be the whole thing could be removed and returned to stock refitting
the battery cover.These days I would probably approach it differently
build a regulated supply and mount a switch and socket into the unit.
Think i used 2 x 5 volt regs with 2 diodes ref to ground to get 6 volts.
Worked alright and was in use for many years.