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Electronics => Projects, Designs, and Technical Stuff => Topic started by: Kilroywashere on March 14, 2019, 11:35:58 pm

Title: 1972 Swtpc Function generator (Wayback Wednesday) even tho its thursday
Post by: Kilroywashere on March 14, 2019, 11:35:58 pm
Hey Got this a bit ago.... I dunno if its working right .. i mean it is older than me ..... maybe the caps are gone....


The pic shows the Ramp I think it looks off... and the offset pull does not work?


I just thought you guys would think this is cool   here is some pics and stuff...


Maybe if you guys can help me find out if its working right ... i have two scopes  so i otta be able to

http://www.swtpc.com/mholley/RadioElectronics/Sep1972/RE_Sep1972.htm (http://www.swtpc.com/mholley/RadioElectronics/Sep1972/RE_Sep1972.htm)

Let me know what you would do to check if this works right

( the ramp is at time div .5 us ampl/div .1 v ) 






Title: Re: 1972 Swtpc Function generator (Wayback Wednesday) even tho its thursday
Post by: Kilroywashere on March 15, 2019, 02:49:02 am
This pic shows the ramp stops  but on my scope the ramp kinna trails off.... what do you think the issue is?
Title: Re: 1972 Swtpc Function generator (Wayback Wednesday) even tho its thursday
Post by: Conrad Hoffman on March 15, 2019, 03:05:25 am
Wow, that was my first signal generator. I don't remember much, but it might well need some new electrolytics by now. I do remember the output opamp was an LM318 in a metal can, and I blew several. Nothing else works quite right. I may have adapted  in a DIP8 at some point. Do you have a manual? Not sure if I still have a copy, but sold the generator long ago.
Title: Re: 1972 Swtpc Function generator (Wayback Wednesday) even tho its thursday
Post by: Kilroywashere on March 15, 2019, 03:30:14 am
I found schematics even! This was apparently a kit you could buy, i don't physically have the manual but this link has a lot of info  prolly build one with it ...

http://www.swtpc.com/mholley/RadioElectronics/Sep1972/RE_Sep1972.htm (http://www.swtpc.com/mholley/RadioElectronics/Sep1972/RE_Sep1972.htm)

The Ramp looks alot different than when i put it on my scope .... the rest seem to work fine tho....

But i don't really know how i would start to find out if it works properly....  I mean i would like to use it  but im sad that i would have to replace the caps ... kina cool they are older than me HAHA
Title: Re: 1972 Swtpc Function generator (Wayback Wednesday) even tho its thursday
Post by: duak on March 15, 2019, 04:55:32 am
I remember when that article came out.  I was in high school and didn't have any money for the kit or even for the Exar function generator chip so I made up the basic oscillator using unmarked  discrete transistors from a grab bag (U test n' save!) and whatever reused junk I had.  It was an emitter coupled oscillator and the voltage waveform on one side of the timing caps is supposed to look like that.  If you look at both sides of the timing caps with a differential amplifier you get a triangle wave.  If you round the points off of that  with a non-linear amplifier you get a sine wave.

A few years later when I had more money, I built a function generator with an Intersil 8038 function gen chip.  I still have that somewhere & it might even still work.