New subject: ST506

5 Apr 2007

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Subject: What is an HP1858-0054 transistor array?
   From: ard at p850ug1.demon.co.uk (Tony Duell)
   Date: Thu, 05 Apr 2007 18:38:14 +0100 (BST)
     To: cctalk at classiccmp.org

I am working on the reset circuit of an HP9816 computer. The output side 
is rrlatively conventional, but it takes an input from a chip that I 
can't identify.

The chip is a 16 pin DIL package marked with the HP house-number 
1858-0054. That's not in my equivalents list. The chip seems to have been 
made by RCA, and tracing the connections to it show that 2 of the pins 
are grounded, but none of them go to any power line. I susepct it's a 
transistor array, therefore (HP1585-xxxx numbers tend to be transistor 
arrays too).

I've unsodered the chip, but trying to work out the internal arrangement 
is non-trivial, partly because there seem to be parasitic diodes, and 
secondly because I am not convinced it's just transistors brought out to 
the pins. There may be a long-tailed pair, for example. It doesn't match 
any of the arrays in my RCA databook.

As I said, it's on the main processor board (the big board at the bottom) 
of an HP9816 computer. It's U115 on this board, at the front left corner, 
just behind the 16MHz clock oscillator can.

Does anyone have any suggestions as to what it might be? Anyone have an 
HP9816 with this IC labelled with somethign other than an HP house number? 
Search for RCA CA3080, 3081, 3082 and also look at 3046.  RCA did a large 
number of transistor arrays (and MOS transistor arrays).

The common layouts were 8 common transisters with emitter(grounded) base 
and collectors brought to pins, 8 common collector (VCC) with emitter and 
base brought to pins.  Others include differential amps, darlington arrays
and some combination arrays.  You have noticed there are a large number 
of parasitic diodes as a side effect of forming the devices on one die.

FYI here is a sample of some of the devices: 

The common collector and common emitter devices were handy for LED
segment and digit drivers but were not limited to those uses.  
Ca3081, ca3082 are examples of this.

Diferential arrays like the ca3026, CA3028, ca3046, ca3049, ca3053, ca3054
were largely used for RF and analog applications but could be handy 
for ECL interface to other logic.

The CA3018, ca3084 were a darlington pair and two uncommitted transistors.

CA3036 dual darlington array with all collectors common.

CA3019 and 3039 diode arrays, handy when one needs matched temperature 
tracking diodes.

Just a few off the top of my head that I'd used never mind the more 
appication specific Opamps and communications circuits blocks (mixers, 
IF amps, Audio amps and TV chroma, sync, video processing). RCA had a 
very extensive line of monolythic devices.

Allison
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-tony 