PNP Ge Rangemaster debugging :)

YellowDog · Post by **YellowDog** » 04 Jul 2020, 13:16

Hi guys,

need some advise with my recently built Rangemaster clone. The pedal works fine in terms of sound and I must admit it sounds darn good with my tweed

I decided to add a DC jack as an addition to the standard 9V battery clip - two options better than one i thought: D
I still didn't test the DC jack, but I noticed that the battery can get petty warm just after few minutes of using it. Probably it shorts somewhere, but dunno where.

I wired it like that: black battery wire to DC jack connect, red one to stereo input jack's ring (to have a battery on/off while plugging/unplugging guitar jack), the DC jack pin comes to the ground, DC jack sleeve to the board.

Input jack works properly, when the guitar is connected the effect works, when I unplug the input jack, it turns off. But the battery heating is worying me.

Did I messed up the battery/DC jack wiring?
I've used a "barrel" style DC jack, like this one:

https://www.pcboard.ca/dc-power-connect ... mount.html

There is also an articke on electrosmash.com states about Rangemaster:

"PNP Positive Ground: it is the original circuit. It sounds fantastic but the problem with it is that if you want to use an external DC adapter (and not only batteries) it will create a short circuit (see how the input and output jacks are referenced to +9V and not ground). The original box never faced this issue because it only works on batteries..."

Kind of weird as I saw plenty od PNP Ge Rangemaster's clones with both DC jack and battery clip and they didn't have any charge pumps etc.

Any ideas?

plush · Post by **plush** » 04 Jul 2020, 14:00

I guess, you are shorting your battery through the metal jack to enclosure (common ground)

You should revisit your wiring. Also do check the polarity.

soulsonic · Post by **soulsonic** » 04 Jul 2020, 19:47

YellowDog wrote: ↑04 Jul 2020, 13:16
Kind of weird as I saw plenty od PNP Ge Rangemaster's clones with both DC jack and battery clip and they didn't have any charge pumps etc.

Any ideas?

You can realize negative ground with a PNP Rangemaster (or any other PNP circuit, like a fuzz) by reversing the circuit so it looks "upside down" in the schematic. For example; 9v negative is connected to ground, so now the Emitter resistor is no longer connected to ground, because it is still connected to the positive. The lug of the volume control is now connected to ground, where before it wasn't, etc... understand what I mean?
To be sure this works reliably, it is good to have a large capacitor bypassing the power supply, at least 100uF, and a 100 ohm resistor in series before this also helps to ensure it is stable. I've done this many times and works like a charm. I've completely given up using charge pumps with PNP boosts and fuzzes, because it's not necessary if the power rails are sufficiently decoupled.

YellowDog · Post by **YellowDog** » 05 Jul 2020, 08:54

Thanks guys. I did many FF style pedals using DC jack + battery clip wiring which worked properly. Thought this Rangemaster circuits won't be an exception.

YellowDog · Post by **YellowDog** » 06 Jul 2020, 10:29

I also thouht it may shorts because of enclosure so I've unscrewed DC jack and isolated it with insulating tape. I made sure it won't touch any metal parts. Battery became warm once again.

I don't understand exactly why input and output jacks are referenced to +9V and not ground, as I can read on electrosmash.com. This is the first time I see sucha thing. I'm not super experieneced but I'm building different clones with mods for some time now nad never had circuit working like that.