Motorola transistor colour code?

[suebutcher]

Is there any rhyme or reason to the colour stripe code on the old Motorola gold-pin TO92's? They don't correspond to the transistor type number, and there can be different colour codes appearing on the same type. A date code maybe?

This photo from Ebay apparently shows several codes on the same type of transistor.

[Terry_VK5TM]

There doesn't seem to be any definitive reason for it, possibly something to do with in house testing or sorting seems common speculation.

It wasn't only Motorola that did it, quite a few other manufacturers did the same.

[Ed_Dinning]

Hi Sue, we used to by them from TI that way, they were gain band sorted (BC182/ 212 types) Some later types went to A,B,C suffix

Ed

[Radio Wrangler]

There's no guarantee that different manufacturers used paint colour codes the same way. So one make isn't a guide to any other.

There is a similar problem with coded colours of paint on ferrite and carbonyl iron toroids, different manufacturers using the same colours to denote quite incompatible types of materials.

It's likely that the only people who know their meaning live around Phoenix/Scottsdale.

David

[paulsherwin]

Motorola were notorious for using obscure house codes on their transistors. They seemed to prefer to supply manufacturers like that rather than using standard codes - no idea why.

[Leon Crampin]

It would probably be customer driven. A board full of TO-92 devices differing in polarity, gain, ft, etc. would be impossible to check quickly on final assembly inspection. The stripes make this easier. Of the devices for which I was responsible, in-house coding and the strict defining of other seldom specified parameters such as solderability was the norm.

It's the only way to make a decent product of lasting usefulness.

Leon.

[G6ONEDave]

Interesting that there is a M752 and some of the transistors have violet, green, red as the colours. Are those colours on that device and if so looks like normal resistance number colours. It's not something that I've thought about, I just go off the printed type number.

Dave

[G6Tanuki]

"House codes" for transistors, and various colour-stripes, seem to have been widespread; yes we're all familiar with the colour-codes indicating gain on the likes of the 2N2926/3906 transistors, but I've got a bunch of the little "Jelly-bean" Fairchild transistors here [the ones with a dull brown ceramic bottom and a shiny brown domed Epoxy-topping] which have colour-smudges whose significance I have never heard explained.

I suspect that quite a few of these colour-blobs were internal manufacturing-things, if you had several production-lines whacking-out identical transistors, you'd have each line's output identified by colour-blobs, so when samples were sent to QA for testing they could identify which line any not-quite-up-to-spec parts were coming from.

[suebutcher]

Originally Posted by G6ONEDave

Interesting that there is a M752 and some of the transistors have violet, green, red as the colours. Are those colours on that device and if so looks like normal resistance number colours.

I've seen a Motorola 2N5458 with colour stripes for "5-4-8" on it, but none of the Motorola bipolar TO72's in my junk box have a colour code related to the 2Nxxxx number.

[barrymagrec]

Many years ago a colleague got hold of the circuits for a Dolby noise reduction system and decided he`d copy it. All the transistors were Motorola types with strange numbers so he contacted Motorola and was told that they were "special" types for a particular customer and no, they wouldn`t be supplying him with any.