Hi all,
Anyone seen one of these before? The IC itself has four bjts on a single die according to the schematic, but - again according to the schematic - there's no connection for whatever this thing mounted on top is, which resembles a very thin button cell. The board it comes from is dated 1970, so unless you're an old geezer, you won't recognize it anyway.
Correction! Apparantly there are *5* BJTs on this chip (U973 on the schematic) - and being as this is a 14 pin chip, there's a pin short! Weird.
Here's the section of the schematic:
Well, you've had more luck than I did with that part number. My searches threw up nothing at all. The IC you've linked to may well be a suitable replacement, but that's not really what I was curious about. The encapsulation is white and has something mounted on top of it. I'd be interested to know why it's white and what the disc-shaped object on the top is. As far as I can tell, this white chip is not the original. The original resembles the one you linked to. So.... what's the deal with the white encapsulation and the disc thing on top of this usurper?
It could be a hermetically-sealed ceramic package. The die would have been mounted inside a cavity, wire-bonded to the leads, and then the lid soldered or weled on in an inert atmosphere. Back in the day plastic packages were notoriously bad in terms of moisture resistance and hermetic packages ruled where reliability was needed.
RCA made transistor arrays in DIP packages; the white ceramic dates it from the early days, but plastic DIPs might still be in production.
the schematic section (pin numbers) is consistent with CA3046 and CA3045. The CA3045 was the ceramic-package variant, but specifications are very similar (CA3045F was the brown-ceramic frit seal package, you've got the CA3045 with white ceramic). The IC has five, not just four, transistors.
Oh, the thing on top is the lid; it's grounded (to pin #13, which is to be held non-positive with respect to other connections, it's the IC substrate).
So it's possible to pop it off? Wow. Never come across one of those before. Be interesting to take a look inside....
Yes, it has five transistors (I did correct myself earlier on up the thread). However, it's a 14 pin package and 5 BJTs require 15 connections!
Ignore that! I've just spotted they've internally tied together the emitters.
The full TEK part number is 156-0065-00
If you don't care about reliability, you can probably just replace it with 5 TO-92 transistors. Just shove the leads into the 14 pin socket. If you want thermal tracking in the differential pair (U973A and B), use matched TO-18 packaged devices and some insulating thermal glue to hold them together.
This stuff should work for good insulation, high thermal conduction, and moderate ease of removal is you screw it up:
Good luck.
Thank you, Jeffrey, you're a credit to Usenet!
Also might be interesting to buy a CA3045 and fix the damn thing.
Are you even sure it's failed?
RL
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