IBM transistor replacements

Bill Gunshannon bill.gunshannon at
Sat Nov 27 14:34:54 CST 2021

On 11/27/21 3:17 PM, Van Snyder via cctalk wrote:
> On Fri, 2021-11-26 at 22:33 -0800, Brent Hilpert via cctalk wrote:
>> On 2021-Nov-26, at 1:52 PM, Al via cctalk wrote:
>>> A while ago I received an IBM 3286 printer, annoyingly some of the
>>> transistors in the printer section have been corroded. What I am
>>> having trouble with is reading the part codes and finding a modern
>>> equivalent of them.
>>> There are two types.
>>> One has a Ti logo and two sets of numbers (attached). Does anybody
>>> know which numbers are the part numbers and if they are IBM house
>>> numbered?
>>> Photos of the Ti transistors and card assembly:
>> Have you checked/measured whether they're actually faulty? Yes, they
>> look terrible, but that doesn't mean they're faulty. It looks like
>> minor corrosion of the steel case under its plating; unless it's all
>> the way through the die is probably fine and cozy inside. The
>> electrically active parts of the transistor typically aren't as
>> susceptible to corrosion as the steel case is.
>> (Notable exception to this being 70's-era TI ICs with plated steel
>> pins. I've also seen some Motorola ICs with corroded pins).
> The Computer History Museum in Sunnyvale, CA has two IBM 1401's that
> are in operating order. One of the problems they had in getting one of
> them to work was that some of the IBM transistors also have plated
> steel leads that had rusted through. Ask Rob Garner <robgarn at>,
> the leader of the 1401 restoration project, if he recognizes the
> numbers.

Make sure you keep the room air conditioning in working order if
you want an operating 1401.  :-)


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