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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 15th Oct 2021, 4:43 pm   #1
Devonboy
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Default 2N 3055-2 ( yes -2 )

Hoping someone can shed light on this vintage version of the ubiquitous 2N3055.

The only mention I can find for them is an ad selling them as "ultra rare".

Last edited by Station X; 15th Oct 2021 at 5:48 pm. Reason: Forum rule compliance.
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Old 15th Oct 2021, 6:33 pm   #2
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Default Re: 2N 3055-2 ( yes -2 )

Are you looking to use them in an audio amp?

Be very careful re: fakes. I haven't seen the 2N3055 faked personally, but considering it was used in plenty of now-desirable vintage audio designs, it wouldn't surprise me if there are fakes out there.

I'd have to sniff around some of my pieces that use the 2N3055 to see if any have the -2 designation. Can't help there, sorry!
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Old 15th Oct 2021, 6:41 pm   #3
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Default Re: 2N 3055-2 ( yes -2 )

Hi, some of the 2N3055's sold back in the day from the cheapie suppliers were manufacturers fall outs and used any sort of die as long as it met the V & I specs, some were high Ft types that could cause oscillations in some audio amps.

Sounds a bit suspicious

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Old 15th Oct 2021, 7:42 pm   #4
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Default Re: 2N 3055-2 ( yes -2 )

2N3055 exist in two versions - hometaxial and epitaxial.

The earlier versions had limited HF gain; later versions had better specs and would happily serve as 'top band' RF-amps at 1.8MHz.

If you had to replace a failed 'early' 2N3055 in an essentially DC circuit - something like a voltage-regulator - and you used a later top-band-PA version, you could often run into oscillation and instability issues that the original circuit's designer never had to deal with.
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Old 15th Oct 2021, 8:50 pm   #5
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Default Re: 2N 3055-2 ( yes -2 )

Quote:
Originally Posted by Devonboy View Post
Hoping someone can shed light on this vintage version of the ubiquitous 2N3055.

The only mention I can find for them is an ad selling them as "ultra rare".

Is there any other markings on the transistor?
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Old 15th Oct 2021, 9:55 pm   #6
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Default Re: 2N 3055-2 ( yes -2 )

If the transistor is a Motorola branded one, an explanation I have seen is that it is the HFE grouping.

And the reason for the grouping was to have similar/matched HFE when used in parallel such as in power supplies.

How accurate that is, I don't know, but the only explanation I have seen for the -2

Some data https://alltransistors.com/transisto...ransistor=2779
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Old 16th Oct 2021, 11:12 am   #7
Devonboy
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Default Re: 2N 3055-2 ( yes -2 )

Many thanks for all the replies but this one stood out.

My interest is as I have a Weir 761.1 with both outputs using a 3055 and a 3055-2 in parallel, all Motorola. I replaced 1 of the 3055s a few years ago but this time it's a 3055-2 that has blown together with the 1R2 2.5W emitter resistor of the coupled 3055. Chicken or egg? The 3 that I have not so far replaced all look very original.
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Old 16th Oct 2021, 3:24 pm   #8
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Default Re: 2N 3055-2 ( yes -2 )

According to Towers the -2 is a voltage rating being VCE at 40 max. There's no voltage given for VCB, VED max at 7v, IC max 15A, HFE 10/70 and HFE bias as 3A. Hope that helps.

Dave
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Old 16th Oct 2021, 4:08 pm   #9
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Default Re: 2N 3055-2 ( yes -2 )

Quote:
Originally Posted by Devonboy View Post
Hoping someone can shed light on this vintage version of the ubiquitous 2N3055.

The only mention I can find for them is an ad selling them as "ultra rare".
Such a suffix can mean anything. Maybe a manufacturers name or preferably some pictures could shed some more light on this.

If it's a standard manufacturers suffix, it can mean better or worse specs, or some kind of binning. If it means a lower Vce spec as suggested above, it might be rare, but also rarely useful.

Of course 'ultra rare' is a red flag in itself, especially when it's a variant on a common type.
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Old 16th Oct 2021, 4:17 pm   #10
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Default Re: 2N 3055-2 ( yes -2 )

I have a vintage 2N3055 with a suffix of B, made by the people with a big S. Made in 1973, probably used in computer PSU's. One datasheet says it has a higher power output. Les.
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Old 17th Oct 2021, 1:51 pm   #11
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Default Re: 2N 3055-2 ( yes -2 )

Apologies as my post yesterday was meant for you instead of generally.
Still don't understand the use of the 3055-2 to attempt hFE matching.
Given that each pair are closely mounted and with emitter resistors I'm assuming old age or new compound needed.
Not sure yet whether a straight swop to mosfets is possible in this application.
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Old 17th Oct 2021, 9:48 pm   #12
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Default Re: 2N 3055-2 ( yes -2 )

I tried a straight swap to MOSFET's in a power supply and it didn't work, so probably not.

As others have said, replacing old 2N3055's with modern ones may entail some taming with bypass caps to keep them stable.
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Old 18th Oct 2021, 2:16 pm   #13
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Default Re: 2N 3055-2 ( yes -2 )

In the interest of educational info, I am attaching a jpg of the page from Towers International Transistor Selector, which covers the 2N3055 range of semicomps. Hope tis clears up some questions. I also hope that I'm not breaking any forum rules.

Dave
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Name:	Towers page.jpg
Views:	135
Size:	88.5 KB
ID:	243673  
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Old 18th Oct 2021, 2:19 pm   #14
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Default Re: 2N 3055-2 ( yes -2 )

I'm afraid on my machine that's unreadable.

Cheers

Mike T
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Old 18th Oct 2021, 3:11 pm   #15
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Default Re: 2N 3055-2 ( yes -2 )

From memory, back in 1971 I used a lot of Motorola 2N3055s and was told by the supplier (Celdis Ltd, of Reading) that the Motorola aluminium cased 2N3055s were filled with silicon grease for added reliability and must say I had very few failures when making amplifiers for the disco world.
I then started using 2N3773s as they could handle more power and a higher Ce voltage; 120 volts as opposed to the 3055 of a mere but very respecable 70 volts.
I am sure I still have a few NOS Motorola versions from the 70s. I used to purchase them in trays of 100 at a time.
If I can find them, I will pm you for your address as I no longer need them.
Failing that I would fit 2N3773s. Similar hfe and frequency range.
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Old 19th Oct 2021, 9:39 am   #16
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Default Re: 2N 3055-2 ( yes -2 )

Hi Mike, sorry the 2N3055 page image is not readable on your equipment. I checked it on my mobile phone and got the same result, strange as it opens up normally on my computer. Anyway I've rescanned it at a higher resolution and am attaching it here.

Dave
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Name:	2N3055 page.jpg
Views:	72
Size:	53.9 KB
ID:	243738  
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Old 19th Oct 2021, 10:25 am   #17
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Default Re: 2N 3055-2 ( yes -2 )

Unfortunately no matter how high a resolution you scan at the forum software will downsize it to keep the file size down.
It is always better to scan documents to pdf, the forum size limit for pdf is higher than for images.

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Old 19th Oct 2021, 11:17 am   #18
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Default Re: 2N 3055-2 ( yes -2 )

Just crop the image, before uploading it, to show just 2N3055 variants.
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Old 19th Oct 2021, 3:01 pm   #19
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Default Re: 2N 3055-2 ( yes -2 )

OK I've cropped the image but have kept the upper section as it includes the headers. I am attaching 2 more versions of this page, hopefully something will work for members.

Dave
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Old 19th Oct 2021, 3:20 pm   #20
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Default Re: 2N 3055-2 ( yes -2 )

That's a really useful scan Dave. I see that the 2N3055E is the only member of the family specified by Towers listing as having Ft of 2.5 Mc/s. Does that mean that all production since about 1970 should properly be labelled 2N3055E?

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