Motherboard Serial Port T Filter Bourns 4220P-601-250/500

Started by sigma7, September 27, 2023, 02:18:45 AM

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sigma7

September 27, 2023, 02:18:45 AM
The Lisa Motherboards include two unusual 20 pin resistor+capacitor arrays that provide EMI filtering for the serial ports.

These are typically Bourns 4220P-601-250/500 and contain a T filter of two 25 ohm resistors in series with the signal, with a 50pF capacitor to ground between them.
Warning: Memory errors found. ECC non-functional. Verify comments if accuracy is important to you.
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