They used to, and still do, call it “tape out”. Although all the old f@rts who even remembered doing it that way at my company retired 10 or more years ago. At the time they were using red tape, feature sizes were down to 2um. 2N3055’s don’t have feature sizes that small - all you need is a magnifying glass.
1991 and 1990. The date codes are pretty clear.
It was quite common to use ‘goop’ die coatings in the early years. 70’s and 80’s Toshiba and Sanken used to, but the coatings were clear. Some of the 3rd party second source stuff still uses white goop inside their TO-3’s, especially the old obsolete stuff where they are still running an ancient process.
Overmolded epoxy packages are NOT supposed to need goop at all if the packaging is up to snuff. When you see it inside a “2SC3281” flatpack, it indicates a fake. Fake TO-3’s will have it too, and the die size and orientation will usually be wrong too. Even those old Teals’s have the die rotated 45 degrees. Anything real, regardless of who made it, will have it done that way.
It was quite common to use ‘goop’ die coatings in the early years. 70’s and 80’s Toshiba and Sanken used to, but the coatings were clear. Some of the 3rd party second source stuff still uses white goop inside their TO-3’s, especially the old obsolete stuff where they are still running an ancient process.
Overmolded epoxy packages are NOT supposed to need goop at all if the packaging is up to snuff. When you see it inside a “2SC3281” flatpack, it indicates a fake. Fake TO-3’s will have it too, and the die size and orientation will usually be wrong too. Even those old Teals’s have the die rotated 45 degrees. Anything real, regardless of who made it, will have it done that way.
2N3055 was first mentioned in this old databook under
http://www.introni.it/pdf/RCA Transistor Manual 1964.pdf
on page 291
I guess, first announcement and advertisement of RCA's 2N3055 must to find anywhere in this magazine archived as PDF files under
https://worldradiohistory.com/Archive-All-Audio/Audio-Magazine.htm
probably between 1962 and 1964.
Who know the associated issue ?
The Maplin amp simply cheated. They just assumed you could use a modern 2N3055 in place of an MJ15015. Sometimes you could. Sometimes you couldn’t. Most modern 3055 will pass the 15015 spec. But you will find some that don’t. If ON Semi sold the batch as 2N3055, some from that lot failed the higher spec and they binned them down. Roll the bones (Or give the Dabo wheel a spin).
+/-55V with 2 pair 15015/016 would usually hold up. At 8 ohms definitely, 4 ohms most of the time. Not at 2. At 2 you’d probably take out the drivers due to the base current they want.
check out post #503+505 under
https://worldradiohistory.com/UK/Industrial-Electronics/60s/Industrial-Electronics-1965-01.pdf
The first ad that I can find for a 2N3055 appeared in the Feb 28, 1964 issue of Electronics magazine. It is located on the last page (64) (also known as the 4th cover) in the following link: https://worldradiohistory.com/Archive-Electronics/60s/64/Electronics-1964-02-28.pdf
NOTE: BTW, I could not find an ad for a 2N3055 in Electronic Design magazine around this time period (1964).
The URL was incorrect. It must read as follows (for looking pdf attachments of early advertisements from 2N3055):
check out post #503+505 so as #517+518 under
https://www.diyaudio.com/community/...tary-power-output.157430/page-26#post-7468340
I suspect the Tesla 2n3055 is a rebadged KD605 or similar.
Tesla transistors have that characterestic orange silicone potting goop.
Noopy over on eevblog probably has more info on -
https://www.eevblog.com/forum/projects/transistors-die-pictures/325/
https://www.richis-lab.de/Bipolar46.htm
2N2222 -
An interesting interrview with Jack Haenichen here on the development/history of the 2N2222 and other transistors - it is
a multi page interview - follow the links at the end of the page
http://www.semiconductormuseum.com/Transistors/Motorola/Haenichen/Haenichen_Page7.htm
Tesla transistors have that characterestic orange silicone potting goop.
Noopy over on eevblog probably has more info on -
https://www.eevblog.com/forum/projects/transistors-die-pictures/325/
https://www.richis-lab.de/Bipolar46.htm
2N2222 -
An interesting interrview with Jack Haenichen here on the development/history of the 2N2222 and other transistors - it is
a multi page interview - follow the links at the end of the page
http://www.semiconductormuseum.com/Transistors/Motorola/Haenichen/Haenichen_Page7.htm
I would say otherwise , "2N3055 to KD605"
Those die can't qualified for 2N3055 then mark as KD605
That's the case
interesting information - thank you for this links. In the attachment I have save this interesting gif-file. This makes it easy to understand that the parameters of old fashioned power BjT devices in the kind of 2N3055 change during dynamic operation - and audible compression effects similar to those of too small power amp transformers occurs during music playback.
Certainly amp models made use of connecting many BjT's in parallel mode with high value emitter resistors (>1Ω) to reduce this effects - go to
https://parttimeaudiophile.com/2022/11/11/dan-dagostino-momentum-s250-mxv-amplifier-review/
https://www.audioexchange.co.za/krell_history/
https://www.whatsbestforum.com/threads/the-dynaudio-arbiters-are-here.10048/
https://www.tnt-audio.com/sorgenti/trinity_tech_e.html
as examples from modern power amps.
Then the effect of the first attached file is of course less pronounced during impulse peaks while music playback
Under
https://web.archive.org/web/20090221041024/http://www.higherfi.com/amplist/amplist.htm
are mentioned more examples.
check out also this site:
https://www.diyaudio.com/community/...n-place-of-one-output-transistor.61627/page-2
What vintage amp models (maybe for public address applications) are there, where was make the same with this old fashioned BjT versions ?
Thanks for an advice.
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VIPINSAINI20, These are from Harris and I think they are manufactured in the year 45th week of year 1990. I got IRF350 in the year 1985 from US which bears code of 8250 which I think is 50th week of 1982.
May be it is my assumption.
https://www.diyaudio.com/community/threads/my-little-cheap-circlophone-c.189599/page-100
May be it is my assumption.
https://www.diyaudio.com/community/threads/my-little-cheap-circlophone-c.189599/page-100
Has anyone seen 2N3055H transistors made by Sanken? My suspicion is that these are counterfeit. Regarding the difference between the 2N3055 and 2N3055H: The H suffix is for "Hometaxial". The Bedini 25/25 used 2N3055H types only. The manufacturer was emphatic that using the non-H type would lead to premature output stage failure.
