Hi folks. I got lost on the internet and now I'm here, against all odds (I always assumed the best pedal is a cable, and I know next to nothing about electronics. What I'm really good at though is asking 3 different questions in a single forum post.)
I recently discovered bits of this soviet RC car that I got somehow when I was about 6 and noticed that the transmitter has 3 Germanium transistors and a diode, and the receiver has a bunch of silicon components. The more I looked at it the more like a fuzz it looked. What can I build out of this, and what are some of these components? What I have here:
1) 2x MP40 GE transistors, PNP. One has about 20+ and the other about 30 gain.
2) 1x P416A transistor PNP, 38 gain.
The gain is after leaks, which are around 10%ish.
3) KT816B, SI, PNP, 105 hFE
4) KT817A, SI, NPN, 71 hFE
5) B0788, SI, PNP, 71 hFE
6) a GE diode, a SI diode,
7) a bunch of things that look very much like transistors, same case but different color as the B0788 (names: B W8, A 8806, B W7) but don't seem to act like them on the tester..
My first attempt was building a fuzzrite with the two MP40s. I used the second schematic here (http://diy.smallbearelec.com/Projects/FursRite/FursRite.htm). It sounds quite fuzzy, but sort of gated. It'll eat a weaker note once in a while, and isn't particularly loud and strong if not maxed out. The voltages on Q1 are 6.95V, and 0.09V, Q2 1.6V, and 0.07V. Quite different.. I noticed the schematics isn't symmetrical anymore for the GE version, should I look at a different PNP one?
Other designs I was looking at (perhaps in addition to this one?) was a Harmonic percolator with the 38 gain GE PNP, I suppose the 71 gain might not be enough? I guess I could pull a modern transistor out in the worst case.
What about a tone bender? The 3 GE transistors aren't going to be enough, right? I got an extra OC44 somewhere...
Thanks in advance for any suggestions and wisdom. Maybe some of it sticks!
Try a Rangemaster. Odds are that they won't be low leakage + proper gain devices for fuzz (other than say, FZ-1). The best bet for those is buying pre-matched transistors from Small Bear etc! But Rangemasters are forgiving - use a breadboard. If you get 1 working out of 3 transistors, you're doing well :)
Quote from: GibsonGM on May 06, 2024, 01:52:51 PMTry a Rangemaster. Odds are that they won't be low leakage + proper gain devices for fuzz (other than say, FZ-1). The best bet for those is buying pre-matched transistors from Small Bear etc! But Rangemasters are forgiving - use a breadboard. If you get 1 working out of 3 transistors, you're doing well :)
Well, I already made two ages ago, I think that's what my spare OC44 was for..
I thought most Russian transistors were low leakage?
Quote from: mozz on May 06, 2024, 02:08:58 PMI thought most Russian transistors were low leakage?
I don't know what leakage is low... They were like 30ma Vs 250ma or so.
Leakage would be in microamps, usually 50ua for example. I'm just thinking most all Russian transistors I have were very low.
Quote from: mozz on May 06, 2024, 02:59:53 PMLeakage would be in microamps, usually 50ua for example. I'm just thinking most all Russian transistors I have were very low.
Right, I meant 30 microamps, sorry. I think the highest leakage was the P416A at around 60?
You're lucky then, Mozz, LOL. Nothing says you can't try ANY circuit with them...tonebender would be most forgiving I think, and use trimmers to bias it. Just easier to buy some already tested for fuzz face and such. But experimenting on breadboard is FUN! :icon_mrgreen:
Last time I fr*gged with Russian Ge's, I needed about 15 to get a tonebender the way I wanted it...most were very low gain, and it's nice to have something with more punch as Q3.
If the leakage is that low, you may be golden. That's DREAM low (perhaps 300uA, 600uA?? in which case, leakage is not low...over 500uA is a dud for fuzz face, generally). Do you know their Hfe?
As I'm just putting kids to bed I'm saying this out of memory, but I used the measuring-over-2.48k-resistor approach to get something like 0.25v Vs 0.03v on the low side and 0.42 vs 0.05 one the high, with the third inbetween. The silicon ones were 1.05 and 0.75v with no leakage.
Did you use R.G.'s method? Sounds like you did. You may want to do it again (so it's not just from memory!), assure yourself that the leakage is ok, and try something if it is. :icon_mrgreen:
I just built a harmonic percolator circuit out of it in addition to the fuzzrite. It sounds alright but I didn't have time to fully play with it and I didn't add the diodes yet. I might just throw the two diodes I got and see how it works, then replace them with more modern silicon diodes.
The internet thinks the Land Devices HP-2 uses russian germanium diodes, but I'm not certain about this, looking at the photos.
The harmonic percolator sounds pretty awesome. I put one of the MP40s in the Q1. Sounded the best of the three. I put a 2N3904 as a Q2. I also tried the 79 gain soviet KT817A. There wasn't a massive difference but the 2N3904 sounded bigger. A 2n5088 sounded worse I would say.
I then looked at the diodes. I have a silicon and a germanium diode. I mixed them together and after some back and forth settled on placing a 4k7 resistor in front of the germanium one. Does this make sense? It felt smoother that way, I imagine it makes the two diodes hit clipping at around the same time?
I also tried a 1n914 pair, symmetrical or with a 4k7 resistor. It sounded a bit less full.