DIY "Keeley"-TS9 mod questions

[duhvoodooman***]

The GenaralGuitarGadgets (GGG) schematic uses 2SC1815's. I think they are the same pinout configuration.

No, they're not. 2SC1815's have the collector pin in the middle position:

http://www.datasheetcatalog.org/data...oshiba/964.pdf

MPSA18's are the same pinout as the 2N3904's, but much higher gain.

[thegnu]

No, they're not. 2SC1815's have the collector pin in the middle position:

http://www.datasheetcatalog.org/data...oshiba/964.pdf

MPSA18's are the same pinout as the 2N3904's, but much higher gain.

So, I remember one of them was a 2SC1815. Praise the lawd. So, what would be the practical difference between using MPSA18's and 2N3904's, because the legs on my reclaimed MPSA's are stubby, and I've got brand new 2N3904's sitting there.

[duhvoodooman***]

SoSo, what would be the practical difference between using MPSA18's and 2N3904's, because the legs on my reclaimed MPSA's are stubby, and I've got brand new 2N3904's sitting there.

The higher gain transistors will keep the buffer gain closer to unity. You may lose a few percent by going with a lower gain tranny. Shouldn't be a big deal.

[Suhnton]

No, they're not. 2SC1815's have the collector pin in the middle position:

http://www.datasheetcatalog.org/data...oshiba/964.pdf

MPSA18's are the same pinout as the 2N3904's, but much higher gain.

Cheers for the correction (I was too lazy to look it up )

[thegnu]

Hey guys, thanks for the help. You guys are pretty darn friendly, as forum inhabitants go.

I had some MPSA18's that weren't too short I couldn't put small pieces of old heatshrink tubing and twist its feet around. So that's done.

I've got interesting stuff to report (at the very least for future googlers). On the OD-9, the TS808 mod resistors are already in place. As for the Keeley more/less mod, the "4k7" is a 2k2 resitor, and the "51k" resistor was a 20k. So I just let them be.

The Monte Allums tri-gain mod installs a switch that gives you stock 1n914a silicon diode clipping on one side, LEDs on the other, and a blend in the middle. I had some issues with the solder joints falling apart, so I took a little bit of that radioshack board with the copper pads per-hole, so I could mount the mod on a more stable surface. Now I've got asymmetrical germanium diode clipping, and symmetrical silicon diode clipping.

Except I screwed up my switch from resoldering it too many times, and for now, only the germanium diodes are working.

Thanks for your help!

[red]

For future Googlers, as you say , usually looking up the transistor type gives you the datasheet, most often in PDF format, and that shows you a picture of the transistor with the pinout clearly labeled.
Example:

• MPSA 18
• 2SC1815

About lifting traces or solder pads, make sure you're using a proper wattage soldering iron (a 25W should be used for PCB work), and be very careful when desoldering (don't let the desoldering braid, if you're using that, cool and stick to the solder pad and then force it off, and don't pull on the components that are not ready to come out). If a trace does come off, you can fix it with a jumper wire (most of the time a resistor leg can be used for that), or you can scrape off some of the insulating coating from the track near the old solder pad and solder the component leg to that.

As for having the option to switch between clipping devices, my (unsolicited ) opinion is that these things are better done on things that are designed to do that and are more experimental in nature, such as a BYOC OD2 kit.

And finally, about MPSA18 vs. 2SC1815, the swap is not really worth it unless you triple the ammount of distortion your pedal can do, or you're using the pedal with very noisy single coil guitars. Even then, the difference is subtle. I'd be surprised if anyone could hear it in a live situation.

Hope this helps.

[thegnu]

As for having the option to switch between clipping devices, my (unsolicited ) opinion is that these things are better done on things that are designed to do that and are more experimental in nature, such as a BYOC OD2 kit.

Yeah, in retrospect, I don't much care for the switch, but I already have a hole where the switch goes. I'm in a learning and tinkering phase, so there's no harm in playing around as long as I'm careful not to blow things up. And as for removing components, I got the cheapo Radio Shack desoldering iron, and it's made component removal way, way easier that using a regular desoldering pump and desoldering braid.

Thanks for the feedback. Much appreciated.

[Stormrider]

IME the 2SC1815 is already a pretty good device. I don't think there is any point in changing them out in these pedals. If they had used 2N3904's from the factory, then maybe, but I'd let the 2SC's be.

[thegnu]

IME the 2SC1815 is already a pretty good device. I don't think there is any point in changing them out in these pedals. If they had used 2N3904's from the factory, then maybe, but I'd let the 2SC's be.

Again a little further off-topic, if you had a device you were trying to lower the noise floor in, and you changed out the capacitors based on Some Internet Guy's advice, but it made no difference, and it had 2N3906's in it (the PNP version of the 2N3904's, to my knowledge), would you swap them for something else? And what would you swap them for?

This device is a Boomerang+ phrase sampler.