5 ms·

Author here for all your questions about obsolete oscillator circuitry :-)

by kens 5y ago

AdamH12113 5y ago
Nice write-up! Question about the (excellent) schematic PDF -- in the pulse trigger section, the emitter of Q3 seems to be tied to the top of R14, but I don't think that can be right? Is it supposed to be connected to ground?
- kens 5y ago
  You should expect about 90% accuracy from the schematic :-) I didn't check the transistor part numbers, so I kind of guessed at NPN vs PNP. Most likely it's a PNP transistor. But the pinout could also be wrong.
adrian_b 5y ago
Even if I do not have any question, because I happen to be familiar with this kind of circuits, I just want to thank you for your work resulting in one more interesting article. I suppose that there must be many like me, who normally would not feel the need to comment your articles, but who nonetheless enjoy very much reading them. A long time ago, when I was young, I have worked with many devices and circuits similar to those reverse-engineered by you in this series of articles. Unfortunately at that time it was tedious and expensive to make photographic records of such technologies and such work, so now I am sad that I do not have records and the memories fade away. Your articles fill this void and I am grateful for them.
tgflynn 5y ago
I'm curious how you were able to source the parts to replace the burned out transistors and other components.
- kens 5y ago
  CuriousMarc has lots of old transistors, so he found some that worked as replacements.
myself248 5y ago
That sine wave shaping network is blowing my mind! I've always wondered how function generators do that, and I knew filtering would only work at one frequency. The diode-resistor network is all sorts of elegant. Using twelve resistors of carefully chosen values though, tolerance issues must be tricky. I'd imagine laser-trimmed networks being a good fit for that topology. Is that likely used in monolithic function generator chips like the XR2206?
- kens 5y ago
  I looked at the XR2206 datasheet. It has a "sine shaper", but from the schematic it isn't a resistor-diode network. It's not immediately obvious to me how that sine shaper works. https://www.sparkfun.com/datasheets/Kits/XR2206_104_020808.pdf https://www.sparkfun.com/datasheets/Kits/XR2206_104_020808.p...

Author here for all your questions about obsolete oscillator circuitry :-)

by kens 5y ago

Author here for all your questions about obsolete oscillator circuitry :-)

Nice write-up! Question about the (excellent) schematic PDF -- in the pulse trigger section, the emitter of Q3 seems to be tied to the top of R14, but I don't think that can be right? Is it supposed to be connected to ground?

kens 5y ago
You should expect about 90% accuracy from the schematic :-) I didn't check the transistor part numbers, so I kind of guessed at NPN vs PNP. Most likely it's a PNP transistor. But the pinout could also be wrong.

adrian_b 5y ago

Even if I do not have any question, because I happen to be familiar with this kind of circuits, I just want to thank you for your work resulting in one more interesting article. I suppose that there must be many like me, who normally would not feel the need to comment your articles, but who nonetheless enjoy very much reading them. A long time ago, when I was young, I have worked with many devices and circuits similar to those reverse-engineered by you in this series of articles. Unfortunately at that time it was tedious and expensive to make photographic records of such technologies and such work, so now I am sad that I do not have records and the memories fade away. Your articles fill this void and I am grateful for them.

tgflynn 5y ago

I'm curious how you were able to source the parts to replace the burned out transistors and other components.

kens 5y ago
CuriousMarc has lots of old transistors, so he found some that worked as replacements.

myself248 5y ago

That sine wave shaping network is blowing my mind! I've always wondered how function generators do that, and I knew filtering would only work at one frequency. The diode-resistor network is all sorts of elegant. Using twelve resistors of carefully chosen values though, tolerance issues must be tricky. I'd imagine laser-trimmed networks being a good fit for that topology. Is that likely used in monolithic function generator chips like the XR2206?

kens 5y ago
I looked at the XR2206 datasheet. It has a "sine shaper", but from the schematic it isn't a resistor-diode network. It's not immediately obvious to me how that sine shaper works. https://www.sparkfun.com/datasheets/Kits/XR2206_104_020808.pdf https://www.sparkfun.com/datasheets/Kits/XR2206_104_020808.p...