clintrubber

Explanation of colour-code on discrete transistors
« on: June 02, 2005, 04:33:44 AM »
First of all, it's a classification of current-gain, correct ?

I've been wondering, is the meaning of those coloured stripes on discrete transistors universal ? Perhaps somewhat related to the 'usual' colour code ?

I've been browsing datasheets of several manufacturers of some type,
but don't see it indicated. So is there a magic table somewhere ?

(Note it's not about 'dots', which seem to indicate type-no of old transistors).

Thanks,

  Peter


gyraf

Explanation of colour-code on discrete transistors
« Reply #1 on: June 02, 2005, 04:44:37 AM »
Nope, never seen anything systematic in colourcoding of discrete transistors.
..note to self: don't let Harman run your company..

clintrubber

Explanation of colour-code on discrete transistors
« Reply #2 on: June 02, 2005, 04:54:48 AM »
Thanks Jakob, at least now I know  :thumb:  
It is about beta, right ?

gyraf

Explanation of colour-code on discrete transistors
« Reply #3 on: June 02, 2005, 05:50:25 AM »
It would make sense - but I suspect that you can have your transistors custom-coloured to all sorts of specs, depending on what you need. I believe that this is an additional service from certain manufacturers...
..note to self: don't let Harman run your company..

clintrubber

Explanation of colour-code on discrete transistors
« Reply #4 on: June 02, 2005, 06:01:53 AM »
Thanks, I see. This would also explain why datasheets seem to keep silent about it. I thought I saw some type once with some color-info in its datasheet, but have no idea which one it was.

All fine, thanks.

Rossi

Explanation of colour-code on discrete transistors
« Reply #5 on: June 02, 2005, 06:02:25 AM »
It could also be some kind of selction done by the gear manufacturer. I recently talked to a Neumann deveolper. He told me that they put color dots on rejected tubes when they select them for noise. At some point they noticed they received again many of the tubes they already rejected on earlier orders.
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"

clintrubber

Explanation of colour-code on discrete transistors
« Reply #6 on: June 02, 2005, 06:17:21 AM »
Quote
It could also be some kind of selction done by the gear manufacturer.

I'll have a look at what the colours actually are. BTW, it's about the MPSA14, darlington. Couldn't imagine it matters much for most circuits whether the gain is above 10,000 or above 20,000...

Quote
I recently talked to a Neumann deveolper. He told me that they put color dots on rejected tubes when they select them for noise. At some point they noticed they received again many of the tubes they already rejected on earlier orders.

Uh, so the bad ones got out anyway and showed up again in problematic units ?

bcarso

Explanation of colour-code on discrete transistors
« Reply #7 on: June 02, 2005, 10:52:31 AM »
Those striped codes were popular with Motorola and maybe others but I never knew what they meant ;-)

However, they are implied in many Japanese parts such as Toshiba in their beta or Idss sorts:  Y, GR, BL, V for yellow green blue violet.  But I have never seen a Toshiba transistor with an actual color band on it.

In small volume manufacturing we used to paint red on the tops of PNPs because of the constant screwups if we didn't (hand-insert errors).  Then I introduced JFETs and caused a hue and cry---they had to start using blue paint and even some other colors.

clintrubber

Explanation of colour-code on discrete transistors
« Reply #8 on: June 02, 2005, 11:19:32 AM »
from Brad:
Quote
Those striped codes were popular with Motorola and maybe others but I never knew what they meant ;-)

However, they are implied in many Japanese parts such as Toshiba in their beta or Idss sorts: Y, GR, BL, V for yellow green blue violet. But I have never seen a Toshiba transistor with an actual color band on it.

Me neither. Luckiliy the Y,GR etc are added to the marking, so all is good.

Quote
In small volume manufacturing we used to paint red on the tops of PNPs because of the constant screwups if we didn't (hand-insert errors). Then I introduced JFETs and caused a hue and cry---they had to start using blue paint and even some other colors.


I recall seeing Japanese PNP's sometimes having green plastic - good move. I thought I've seen green regulators (neg) as well. And pink elephants, no, green double diodes as opposed to double ones in black for the 'normal' connection.

Quote
and even some other colors

Let's hope it was transparent paint  :wink: - well, I mean, at least Philips discretes have had their marking on top in the past for a while.

Regards,

  Peter

Rossi

Explanation of colour-code on discrete transistors
« Reply #9 on: June 02, 2005, 12:41:12 PM »
Quote from: "clintrubber"

Uh, so the bad ones got out anyway and showed up again in problematic units ?


They didn't use the ones that didn't pass the test. The rejected ones were returned or resold. Which I think is nicer than simply destroying them. A tube rejected by Neumann for, say, a U67 reissue isn't necessarily unusable for anyone else. The only problem was that the same tubes that some of the tubes they rejected turned up again in another shipment. So they put color dots on each tube they tested. When they receive a new shipment they can at least save some time by sorting out the ones they already tested.
"I am not a number, I'm a free man!"
"Hahahahaaaaaa!!!!!"


CJ

Explanation of colour-code on discrete transistors
« Reply #10 on: June 02, 2005, 04:07:28 PM »
Those darn stripes sure made fixin stuff a pain.

Here is a DBX VCA, color coded like Brad said, NPN,PNP, I believe. I have not traced the circuit yet.

What are you going to use the MPSA14 for?

If I can't fix it, I can fix it so nobody else can!
Frank's Tube Page: www.mif.pg.gda.pl/homepages/frank/vs.html
Guitar Amps: http://bmamps.com/Tech_sch.html

clintrubber

Explanation of colour-code on discrete transistors
« Reply #11 on: June 02, 2005, 05:54:39 PM »
Quote
They didn't use the ones that didn't pass the test. The rejected ones were returned or resold. Which I think is nicer than simply destroying them. A tube rejected by Neumann for, say, a U67 reissue isn't necessarily unusable for anyone else. The only problem was that the same tubes that some of the tubes they rejected turned up again in another shipment. So they put color dots on each tube they tested.

Thanks Rossi. Ah I see, so those manufacturers just kept trying...
Indeed a pity to destroy them.


from CJ:
Quote
What are you going to use the MPSA14 for?

It's the suggested darlington for the JFP. Generic darlington is stated to be OK, but since I have a few of these MPSA14 anyway then why not use that one. (Motorola, but all kinds of different colours...  :cry:/ :grin:  )


 

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