Vintage transistor matches

[ennisdavis23]

I am looking for the following transistor matches. These are the numbers on top line and bottom line of to-92

45-1
427

988
428

45-1
431

78-1
407

 

[rjenkinsgb]

It there are no other markings at all, the top number is likely an "in house" part number - they were very common at one time, especially in industrial equipment.

The equipment makers had the manufactures standard numbers substituted with their own part numbers, by the semiconductor manufacturers, as a way of protecting the designs - there were very few, if any, "custom" parts, so anyone knowing all the real ones could just duplicate the designs.

The second line in each is most likely just the manufacturing date; last digit of the year, then week number within that year; eg. 1984 (or 74, or 94 etc.) Week 27, 28, 31 & 07.

 

[Pommie]

If you can draw a schematic then someone here may be able to suggest suitable replacements.

Mike.

 

[danadak]

I recall at NSC there were published lists for transistor markings, and markings for
special screened transistors. Motorola used to do a lot of this. as well. In my library I looked
at 1970 Fairchild Transistor data book, no luck thou.

Regards, Dana.

 

[Nigel Goodwin]

I recall at NSC there were published lists for transistor markings, and markings for
special screened transistors. Motorola used to do a lot of this. as well. In my library I looked
at 1970 Fairchild Transistor data book, no luck thou.

Regards, Dana.

None of that would help with in-house numbers, which are exclusive to the company that orders them.

But basically you don't usually replace transistors with supposed equivalents, you replace them with ones which will do the job. As Pommie said, posting a schematic would help - or even a mention of what they are in, and what they do.

 

[danadak]

None of that would help with in-house numbers, which are exclusive to the company that orders them.

No, thats not the case at all. They were used both for specific customer and for special screens
for broader customer base. Usually not catalog based, rather specific requirements, various
customers, dug up by FAEs in the field. We sometimes shipped to the mark, other times remarked
with customer part number. Or something in between. That being said as the discrete industry
evolved less off spec screening was being done, and the marking systems exploded to the point
no one wanted to deal with them, unless GP margin was stratospheric and/or volumes. My
comments based on being a production EE at NSC with a periodic relationship to Gus Mellick
who ran the discrete applications effort. And later as FAE for Boston region.

"supposed equivalents", yes, we had those tables which were distributed to end customers, and they
were encouraged to do the investigation and qualification for the "supposed equivalents" that they
would choose and be responsible for. Tables were simply guides to help design EE to choose what
to examine.

Regards, Dana.

 

[Nigel Goodwin]

No, thats not the case at all. They were used both for specific customer and for special screens
for broader customer base.

Not really 'in house' then, where an equipment manufacturer orders devices of a certain specification from (usually) multiple manufacturers, and has their own 'in house' numbers stamped on them. The semiconductor manufacturers have no information from those numbers, and why should they care?.

While one reason for this is probably in order to force service agents to buy the correct parts from the equipment manufacturer, it's probably more the fact that they can source the 'same' component from multiple semiconductor manufacturers, thus helping to maintain the supply chain.

'Generally' we used to stock some in-house devices, but often we'd often replace them with generic ones - simply based on what it does, and what shape it is - a TO3 LOPT transistor is much the same regardless of the number stamped on it. Presumably it's slightly more expensive to do this?, as you're often fitting a higher quality part (but that's a good thing), but in-house parts tend to be expensive anyway, as you can't buy them elsewhere.

 

[danadak]

Not really 'in house' then

I guess we have multiple definitions for the term. I'll keep mine as I believe you will yours.

Regards, Dana.