I'm forced to rebuild a 'magnetic amplifier' circuit and PCB. This circuit was originally designed in 1968, and my PCB was assembled in 1972. It's all resistors and caps, with a few small transistors.
Since I have to rebuild the whole thing, I'm having to find current-day items for the components used bade then.
Everything's been easily replaced, except for one item.
An inductor. On the schematics, it's listed as:
L201 0.975 1.025 HY
And in the parts list, it says (sic):
Inductor, Variable 0.975-1. 025 H
The component is cylindrical, about the size of a quarter round, and about 1.25inches high. The only markings on it are:
AE 426-908 7203
AE is the manufacturer logo, and the
7203 is the date code, obviously.
So, while trying to find a 1H inductor, through-hole - they don't exist. All the 1H inductors I've found are essentially small transformers, and definately not possible to mount on a PCB. Searching for the 'AE' and part# yeilds no results, unfortunately. I can transfer these off of the old boards, but would rather find a suitable replacement.
Is it possible they meant mH or uH back then? (Similar to how caps were all listed using the MF symbol instead of uF..?)
Edit: Here's a link to a picasa album. This has three images of the inductor (two of top, one with a 27C020 EPROM for size comparison, and one from the bottom). A GIF of the schematics is also in that album. This circuit takes a signal from a cassette tape player head, magnifies it for use with a handful of gates on another board (not pictured, not in schematics). Point
T on the schematics is the output. The lead coming in from the top above
+16vdc input. The
B inputs at the bottom left is the input from the magnetic head. (With shield connected to
Looking closely at the inductor - it looks like it's dual-wound, and only one winding is used - I believe, since the middle terminal is not tapped/used, the adjustment isn't even used. How strange.
Edit 2: The resistance (DCR) as measured by my beat-up Fluke 177 is 190ohms. This was measured with the inductor taken out of the circuit.