11-05-2018, 05:26 PM
(11-05-2018, 11:53 AM)Crackle Wrote: The IC is a ULN2240 here is some information that I extracted from a large Sprague document.
I think I've found the same document, albeit with a slightly better quality. There is also an application note covering different receiver designs using these chips which might be of interest.
I found it here: http://bitsavers.trailing-edge.com/compo...rcuits.pdf
The data sheet that you posted starts at page 402 of the pdf and the application note, if you haven't already seen it, starts at page 468.
Interestingly there is a reference at the end to a design published in Practical Wireless using the similar ULN2290 but that covers MW, LW, 3 SW bands and FM so might be a bit of overkill for working on your little set.
At least, with the information you now have, you can identify which coil is which by seeing which pin of the IC they are connected too.
Oh, and it appears I was wrong about the ratio detector diodes! I wonder what they are for?
