Want to build a peavey bandit 112 redline or Randall RX120D

[kin0]

Oh I now found that it is written

Black-PRI 220V 50Hz
Red-SEC 6VAC X2 1A
GREY-C.T


Can I get more than 12V out of this?

[J M Fahey]

Hi Kin:
Then you have to turn that transformer 180º (referring to your drawing): both blacks to the left, one straight to one side of 220V, the other to the other side, but through the switch and the fuse holder.
Both reds to the right, to the AC pins of the bridge rectifier.
The 2200x25 electrolytic capacitor will charge to the peak voltage of 12V: 12VACx1.4142=16.97V DC. (in theory)
Substract from that a little over 1V because of diode losses, you'll end with almost 16V DC, perfect for that Velleman Kit (or anyone similar to it).
The grey wire goes unconnected, insulate its free end with some electrical tape.
Good luck.

[kin0]

If I put the + (form the zener regulator) to the circuit I put the - to the ground? If it is right do I have to put the + or the - in the shredmaster

[J M Fahey]

In single supply amplifiers, as this one, "-", "black" and "ground" are all the same.
The "-" from your power supply (PSU) goes to the - of the Velleman and to the - of the Shredmaster.
The +16V from your PSU goes to the + of the Velleman and, through a dropping resistor to the + of the shredmaster.
To make *sure* that the shred receives 9V and no more, you have a 9V Zener from + to ground.

[kin0]

OK, I build the power amp kit and it works fine. I got shocked once then I was turning it off but I'm just fine. The problem is that the resistor in the zener regulator got burned. Is this because I haven't connected the 9V circuit or because something else, and how to fix it.

[J M Fahey]

0) Congratulations on your build. :tu: :tu:
1) Did you use a 330 ohm, 1/4W (or higher dissipation) resistor?
It should be warm to the touch, but not burning or smoking.
2) Do you measure 9V there?
*If* you put the Zener the wrong way, it will drop only less than 1 V; the resistor will dissipate (worst case)= (15x15/330) W=0.7W=700mW; way too much for a 1/4W resistor=smoke and burn.
Use a 330 ohm 1W resistor, it will support even a shorted preamp.
Good luck.

[kin0]

I used 120 OHM 1\2 W and a 5W 9v zener. I haven't checked the voltage but there was smoke and the resistor turned black. I need about 50mA cause I use barber LTD as the clean preamp and the shredmaster as the dist.

Also which switching is better:

[kin0]

any help?

[joecool85]

I didn't read the whole thread, is the switch just for switching between 2 channels on the amp or something?

[kin0]

Yes, it switches between channel 1 (barber ltd) and channel 2 (marshall shredmaster)

[J M Fahey]

Best is the middle one, which switches inputs and outputs.
Do not switch the +9V or any power, it will pop a lot or give you very funky sound for quite a few seconds, until voltages stabilize, or both.
You might also join inputs permanently, switch outputs only, and if the shredmaster injects some faint buzz in the background, use the now spare contact to kill its gain when unused.

[kin0]

and what about the zener rgulator

I used 120 OHM 1\2 W and a 5W 9v zener. I haven't checked the voltage but there was smoke and the resistor turned black. I need about 50mA cause I use barber LTD as the clean preamp and the shredmaster as the dist.

[J M Fahey]

Well, do check the voltage.
Check that you have those 9V and alsothe real voltage across the 120 ohm resistor, to calculate the power it's actually dissipating
W= V*V/R
Up to the rated dissipation, it will be hot but not toasting or burning.

[kin0]

but the resistor have already been burned

[J M Fahey]

Maybe you have *another* spare resistor?