New old schematic: RCA Hobby Circuits Fuzz

[ErikMiller]

Today I received my copy of the RCA Solid-State Hobby Circuits Manual (HM-91) from Alibris.

Lots of fun reading, with the usual wistfulness about how vital the electronics hobby market was back then (1970).

Anyway, there are several circuits of interest to the DIY musical electronics community, including a little theory, basic construction and troubleshooting instructions, an electronic organ, preamps and power amps galore, and....to my surprise at never having heard of it, a Fuzz Box.

The circuit looks to be a Tonebenderish Fuzz Face with input buffer sort of thing. I haven't breaded it up yet, but I intend to, as I do so love that type of circuit.

For the good of the many, I did scan the pages describing the project:

http://www.rawbw.com/~emiller/Euthymia/RCAFuzz/RCAFuzz1.jpg
http://www.rawbw.com/~emiller/Euthymia/RCAFuzz/RCAFuzz2.jpg
http://www.rawbw.com/~emiller/Euthymia/RCAFuzz/RCAFuzz3.jpg

Anyone else ever heard of this circuit? Who will be the first to try it?

[Lonestarjohnny]

I've never seen it, but I'm gonna try it, I like Fuzz circuits also,
Thanks for Sharin,
JD

[toneman]

never seen it either.
thanx 4 postin'
tone

[phillip]

That is a pretty interesting circuit!  It uses NPN for Q1 and Q3, but it uses a PNP transistor for Q2.  From what I could find out (and it wasn't much) the SK3020 was Silicon, while the SK3005 came in the TO-1 package and was Germanium.

The SK3020 cross referenced with 2N2219: "AF Preamp, Vid Amp, NPN Si TO5."  Mouser stocks a 2N2219A that comes in the TO-39 package:

http://www.mouser.com/index.cfm?handler=displayproduct&lstdispproductid=315514&e_categoryid=241&e_pcodeid=51127

The gain range of the 2N2219 more or less falls into the same range as the much more common (and cheaper) 2N4401.

Hope this helps out a little

Phillip

[The Tone God]

That looks familar. Hey I have that book. I think it might have a few other things in it.

Andrew

[J Gagan]

in the 3rd picture it sure looks like 3 Ge trannies to me. I never saw a Si in a straight sided can like that. maybe someone can enlighten me on this

[ErikMiller]

in the 3rd picture it sure looks like 3 Ge trannies to me. I never saw a Si in a straight sided can like that. maybe someone can enlighten me on this

The venerable BC109, for one, is in a straight-sided can.

[J Gagan]

kool , thanks eric

[Fret Wire]

Cleaned up a little.

[phillip]

You can see the emitter tabs on the first and third transistors.  Those are probably the TO-18 metal cans like the BC107, BC108, and BC109 (among others) come in.

Phillip

[brett]

Hi. Thanks for the interesting circuit.
Given that the last two stages look like common emitters (with no emitter resitors), it will probably be important to use Ge and/or low hFE Si transistors in those positions.

Let us know how it sounds.

cheers

[ErikMiller]

in the 3rd picture it sure looks like 3 Ge trannies to me. I never saw a Si in a straight sided can like that. maybe someone can enlighten me on this

The venerable BC109, for one, is in a straight-sided can.

It just occurred to me that the "straight-sided can" you were referring to is probably the TO-1 package, and now that I think of it, I haven't seen any silicon in that package, either.

Contrary to my earlier assertion,  the venerable BC109 comes in a TO-18 package, which is a can with straight sides, but it does have a flange at the bottom as well as a tab for the emitter.

In the photo, the silicons seem to be in a metal package with a tab but no flange. Not sure what to call that package....