| Posted by Shawn S. | September 22, 2017 - 03:25 pm |
| Thank you, much appreciated. Do you have a part number for the germanium diode? Also, Being a project nut, I have several small footprint toroidal transformers on hand. What would be the ballpark specs that would work for this? Thanks in advance. |
| Posted by Steve L. | September 22, 2017 - 08:39 am |
| Hi Shawn, The CD40106B is equivalent to 74C14B and is available at Digikey and other places. (I wish they would indicate that on the "obsolete" page.) The schematic and the parts list in the construction notes have been updated to show the CD40106B as equivalent. Thank you for bringing this up! |
| Posted by Shawn S. | September 21, 2017 - 07:25 pm |
| Is there an exact part number or equivalent for the 74C14B? Mouser and Digi-key doesn't seem to carry them. Remove the B and quite a few places have the 74C14. Any help would be greatly appreciated. Thanks. |
| Posted by Steve L. | October 25, 2013 - 12:16 pm |
| Hi Jesper, Thank you kindly for your nice message. Hearty congratulations on completing the project! I hope that using your new IG-18 gives you as much pleasure as using mine has given me. Before doing this project, I had gone through previous iterations of "greening" the critter, beginning way back in the seventies with an article from the Audio Amateur. While those reduced distortion, they increased settling time and reduced stability. Now when I use it, I recall how it used to waver around the final level and change level across the bands. The way HP's excellent circuit just locks right in on the level seems almost magical in comparison. |
| Posted by Jesper M | October 25, 2013 - 09:13 am |
| Hi Steve, Just wanted to say that your write-up here of the modifications to the Heath IG-18 has been really, really helpful in my upgrading the Heath. Combined with Dick Moore's webpage & good assistance I've just completed the re-build and the oscillator seems to work splendidly should (from < 1Hz to 110 kHz) although I still need to check distortion. So - many thanks for setting up this site & documentation!! Greetings, Jesper Mønsted (Denmark) |
| Posted by Steve L. | June 12, 2011 - 07:44 am |
| Hi Larry, Thank you for the kind comment. I did not notice much hum and the 20-1000Hz distortion measurement was at the floor of the analyzer. It's possible that the folks who dealt with the transformer were actually chasing a ground loop problem. The new board layout has the power supply section comfortably spaced from the audio circuits. I was also very careful about ground connections, as is reflected in the layout diagrams and schematic. So I didn't find a reason to change the transformer situation. Let me know how it goes! |