I'm trying to positively identify this resistor network. Has anyone encountered them before?

An unknown resistor network in a 14-pin DIP package

They were found on a backplane with 96-pin DIN 41612 connectors. It's not a VME bus — A/B/C1-3 are a big rail, possibly ground, and so is A/B/C32 (possibly Vcc). The bus pinout may be ad hoc. It's a relatively old device: early Nineties at the absolute latest, probably mid to late Eighties.

(Apologies for the graininess, it's an available light photo)

  • \$\begingroup\$ Produced in week 21 of 1983. \$\endgroup\$ – stevenvh Aug 31 '12 at 13:55

As Jonta says what you have there is a TTL Dual-Line Terminator / Pulse Squaring resistor network. An example datasheet is here. The internal circuitry is shown in the figure below:

dual line res network

Specifically you have a 330/470 Ohm version like the on here.

You have commented that you are reading between 60 and 70 ohms between the ground and common lines (pin 7 and 14). This is correct! If you study the schematic above, the equivalent resistance between those two pins would be twelve (330+470) Ohm resistors in parallel, or about 66 Ohms.

As the datasheet linked above states, these resistor networks are used for TTL dual-line termination and pulse squaring.

  • \$\begingroup\$ Thanks. I keep underestimating just how much CMOS has changed my way of thinking. I can't imagine designing something that consumes this much power just to idle along. Not to mention the packages get hot (which is only to be expected... nowhere else for all that energy to go) \$\endgroup\$ – Alexios Sep 1 '12 at 8:19

It looks like the top part is a part number and it looks a loot like the order number for instance this one.

If you look at the part number that would mean:

  • 760 : 14 pins
  • 5 : Dual terminator
  • 330 : Value of R1
  • 470 : Value of R2

Using the schematic and a ohm meter, you should be able to verify / rule out this.

  • \$\begingroup\$ Yup, that was my expectation. I'm reading 390Ω consistently, though, and there's what looks like a 60-70Ω resistance between pins 7 and 14, which is why I asked the question in the first place — I think the nets are b0rken somehow. \$\endgroup\$ – Alexios Aug 31 '12 at 13:57

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