I need the assembly manual for a SWTPC 202-C headphone amp which I picked up. It needs a recap at a minimum, and likely other work.
This is a Class A, low-distortion amp from the early 1970s.
Some of the members have mentioned building these, but nobody seems to have retained one or the documentation for it. I've searched the Interwebs, including SWTPC.com, but didn't find any technical information about it. So any documentation or leads would be greatly appreciated.
This is a Class A, low-distortion amp from the early 1970s.
Some of the members have mentioned building these, but nobody seems to have retained one or the documentation for it. I've searched the Interwebs, including SWTPC.com, but didn't find any technical information about it. So any documentation or leads would be greatly appreciated.
It's possible that plans were published in Popular Electronics, if you can find a searchable index of back issues. If all else fails, reverse engineering it wouldn't be too hard. Once you derive a schematic, if you don't know how to analyze it to determine normal operating voltages, folks here should help out.
What I did to create a schematic for an old CM Labs amp was to take a digital picture of the back of the PC board, backlit to make the traces stand out, then manipulated the image further to get a grey/white picture. Print it out reversed (component side view), then draw in the components. Finally, draw something resembling a schematic with the components in appropriate locations (signal flow left to right, positive rail on top, negative on the bottom).
What I did to create a schematic for an old CM Labs amp was to take a digital picture of the back of the PC board, backlit to make the traces stand out, then manipulated the image further to get a grey/white picture. Print it out reversed (component side view), then draw in the components. Finally, draw something resembling a schematic with the components in appropriate locations (signal flow left to right, positive rail on top, negative on the bottom).
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That is an excellent suggestion, but unfortunately this was one of the handful of projects that NEVER made it into Popular Electronics, or any other publications as far as I can tell. It isn't listed here:
www.swtpc.com/mholley/Catalog1972b/Catalog1972b.htm
It's always easier if someone has the manual with a schematic, and I figured with all the SWTPC gear sold someone should have one. They can't all have been lost...
That's a very clever trick which would save time, but I hope my efforts don't come to that.
I did a kit report for The Audio Amateur, many many years ago. It was subsequently lost in shipping. 🙁 I'll check and see if I have the manual.
The little amplifier ran pretty hot, being Class A, of course.
The little amplifier ran pretty hot, being Class A, of course.
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