positive ground green ringer

[bentium]

hi guy's


i want to convert the green ringer into a positive ground pedal, so i can put it into 1 enclosure with a FF

The reason why the green ringer has to be converted & not the FF is that i have a pretty large amount of NOS ac128

starting from the GGG schematic:

1) switch polarity of C4
2) npn => pnp (so change the 2n5088 with AC128 or so)
3) pnp => npn (2n5088 or so)
4) change polarity of power supply connection


is this correct?

[tiges_ tendres]

You'll have to completely re bias the transistors as well.  You might get lucky, but in most cases you cant just drop a Germanium transistor into a silicon circuit without doing some tweaking of resistor values.

Why not do this:  Get it working as normal, Negative ground, then take voltage measurements of your transistors.  Once you've done the stuff you listed, try and drop in a germanium and see what voltages you get then.  This is assuming that your germanium transistors are decent low leakage to begin with. 

My only other advice?  use a Charge Pump to create a bipolar supply and power the pedals this way.  This will mean you wouldnt have to tinker with the green ringer at all, and you'd be able to run both pedals in the same box, from the same supply.

[bentium]

isn't it better that i use a max1044?

[tiges_ tendres]

isn't it better that i use a max1044?

Yep, that charge pump would certainly do the job.

[rrroo]

max1044 is expensive and hard to find. also takes space and requires more wiring etc. has anyone built a positive ground green ringer? i'm working on a germanium fuzz face + octave project too...

[DavenPaget]

max1044 is expensive and hard to find. also takes space and requires more wiring etc. has anyone built a positive ground green ringer? i'm working on a germanium fuzz face + octave project too...

From the makers of the 'PIC' Microchip , TC1044 . Not that hard , certainly not expensive either .
And the MAX1044 is certainly cheaper then the LTC1044 , according to the last time i checked , and yes , it's rare because not many DIP MAX1044's are left out there . TC1044SEPA is the more extreme weather performing version . ( compared to SCPA )

[petemoore]

  Should work with either polarity, IIRC there's a diagram for both + and - Gnd. at GEO or someplace.
   Start with a schematic and invert anything 'invertable'...anything with a polarity sign, including the diode inside the transistors, caps, diodes [and of course battery]...if it has a polarity sign, it 'cares' about polarity and could-or-will be damaged by applying an inverted polarity voltage.

[rrroo]

geofex has schematics for both PNP or NPN versions. in the schematics the ground stays the same though.

does changing the ground from negative to positive mean that i have to change from NPN to PNP? or can I stay with NPN?