test the IC 2519

I did a Google search and found this information:

Testing a shift register IC with a multimeter primarily involves checking for short circuits and verifying supply voltage (VCC) and ground (GND) connections. Set your multimeter to diode or continuity mode to check for shorts between VCC and GND. A near-zero reading indicates a likely dead, shorted IC.

Steps to Test a Shift Register with a Multimeter:

1. Identify Pins: Locate the VCC (positive) and GND pins using the datasheet. Generally, VCC is near a bypass capacitor.2. Power Off - Continuity Check: Turn off the circuit. Set the multimeter to continuity (beep) mode. 3. Check Short Circuits: Place probes between VCC and GND pins. A constant beep or near zero ohms resistance means the  IC is likely shorted internally.4. Diode Test (Power Off): Set to Diode Mode. Place the black probe on GND and red probe on input/output pins. A healthy  IC usually shows a voltage drop between 0.4V and 0.8V (400 - 800 mV).5. Power On - Voltage Test: Apply power. Set the multimeter to DC Voltage. Check that VCC pin is receiving the correct  voltage relative to GND.

A multimeter cannot fully test the logic function of a shift register (shifting bits). For that, you need to monitor output pins while providing a clock signal or use a logic analyzer, or connect the outputs to LEDs to see the data shifting.

Possible helpful links:https://www.applefritter.com/files/signetics2519.pdfhttps://www.utsource.net/itm/p/1884790.html

I hope this is helpful in some way. I am not knowledgeable on the 2519B IC. But understanding how the IC works is a good place to start (in my opinion). 

Joe

It has been my experience that a lot (40-50% ?)  of the 2519N I got in the early phase of my kits were bad, and about half of the bad ones were dead right out of the tube, and another half failed during the first ~3 days (or so) of the burn-in (running my diagnostics page in an Apple-1). Typically, these still showed something going on (on the screen) so they did not die, but limped along in some dysfunctional and useless way.

The takeaway from this is that if you buy 2519N, and there is only one source left (in Israel), that you get a 100% function / money back guarantee if it does not work fine in your Apple-1. And you need to do a long test at full clock speed and full output load, so these ICs run at the higher temperature and stress as they encounter in the Apple-1.

All my later kits used 2519B from another source (also in Israel, but a different seller) and these had very few bad ones (~ 3%) and all had the desirable 1976 date codes.

Buyer beware !

- Uncle Bernie