2N3055 Transistors.
 

I have a batch (about 10) 2N3055s, bought as NOS back in 2003. Some have now got tiny traces of rust on the cases (the "can" part of the case rather than the bolted flange). Is this unproblematic - i.e. is the can part normally made of steel?".

Also, would it be possible to tell by inspecting the die of one of them ("sacrificed" for the purpose by cutting off the can) whether it is -
1. earlier homotaxial type (Ft about 2.5 MHz)
2. later epitaxial type (higher Ft)
3. just a good old fashioned fake?

Thanks if you can help.

Mike

Re: 2N3055 Transistors.
 

Don't cut power transistors open - some contain BeO (beryllium oxide), which is highly poisonous.

Re: 2N3055 Transistors.
 

Hi Mike, and welcome to the forum!

I've encountered these transistors in a series pass application in a power supply from the early 80's. The chassis and cases of four transistors were remarkably rusty, but all four were still electronically intact, even though the hardware had rusted through in places.

A bit of fine wire wool will sort the rust if you're going to be running them hot and don't want to use a solvent.

Def don't cut open as Beryllium is indeed perilously hazardous and you will have a control of substances hazardous to health (CoSHH) sitch on your hands in short order!

These aren't high frequency types at all, so simply steer clear of applications where they need to be as there are far more suitable high frequency high power types.

Re: 2N3055 Transistors.
 

I emphasise the warning above. Although the chances are that there is no BeO in these (tends to be more in RF and/or isolated case devices), it is not worth the risk.

Re: 2N3055 Transistors.
 

Thanks Astral Highway, but I have the exact opposite problem - I'm hoping to find that my 2N3055s are the older, lower fT (hometaxial) types to use in the Quad 303 "triples" output stages - so specifically the lower frequency originals. I originally posted this in the "Quad 303 Problems" thread, which was discussing this specific issue, but it got moved to this new thread - so that's the context here. In that thread, Radio Wrangler seems to say that no modern transistor has a low enough fT to work stably in the Quad 303 output triples - though others point out that DaDa Electronics recommend the MJ15003 as workable in the circuit.

Re: 2N3055 Transistors.
 

This https://cds.cern.ch/record/274991 is a CERN technical note describing a 13kA 100V pulsed power supply from 1970 that used 7200 2N3055 driven by 360 more of them.

The 2N3055's were specified to be from Westinghouse. Which is not a name I associated with 2N3055.

Re: 2N3055 Transistors.
 

That's quite an impressive load.

I found out by accident that you can reduce the gain of newer ones by zenering them. This can actually turn into an advantage for once!

Re: 2N3055 Transistors.
 

Almost zero probability in the 2N3055.

BeO is a super combination of thermal conductor, electrical insulator. But in the '3055, the only insulation needed is the two leadout pins - which are glass-bead insulated. The die inside is soldered directly to the header, which is soldered to the base. No insulation needed!

If it DID have BeO inside, you wouldn't be able to throw in in the bin...

Re: 2N3055 Transistors.
 

Precisely why I erred on the side of caution.

Re: 2N3055 Transistors.
 

As the OP seems willing to cut one open if necessary, perhaps someone could answer his original question?

Re: 2N3055 Transistors.
 

Yes indeed.
Just wire up a common emitter circuit with plugs on the leads and feed it with a signal generator to see how far up the frequency goes before the gain drops.

Re: 2N3055 Transistors.
 

If there were any other way of knowing what the likely fT range is, I'd be happy to use it instead of destroying one! As I've said on the other thread, I wonder if Quad specifically and individually selected low fT 2N3055s for use in the 303's triples... The Wikipedia article on 2N3055's suggests a lot of uncertainty over the frequency-gain. Admittedly it must be unusual to be looking specifically for lower fT - so I'm one of the "awkward squad"!

Re: 2N3055 Transistors.
 

Sorry Refugee, I posted my last before your reply showed up. I was afraid it might come down to that - having to sort out a power supply, heatsinks, biasing, etc just to know if they're viable in this circuit. Would this test need to be done with the transistors giving significant power output? Might be as easy to just construct the amp using them and test it?

Re: 2N3055 Transistors.
 

You would need a power supply of about an amp at something like 12 volts.
Then just select resistors to give about 500ma.
It should then allow you to feed it with a sig gen.

Re: 2N3055 Transistors.
 

Refugee, thanks. You mean 500mA emitter current? And base dc bias - about 20mA? Ensure consistent input signal voltage from sig. gen. and then monitor collector signal voltage with o/scope. Safe without heatsink? Probably not.

Mike

Re: 2N3055 Transistors.
 

I cannot help on the issue of opening one up, but I do have a wonderful old 25A psu, probably made in the 70's by the Kingshill company (long since gone) which I found in a dustbin.

It has twelve 3055's all of which were very rusty indeed, but the supply works very well.

B

Re: 2N3055 Transistors.
 

Via a capacitor

Re: 2N3055 Transistors.
 

I also have a thread running with the same subject title as this one, so I'll add a link to it to try to keep all the information together in one place:-
http://www.vintage-radio.net/forum/s...d.php?t=138407

There was also some very interesting information on these transistors in that Quad 303 thread which I should have perhaps linked to in my thread, and maybe will do, but I'll link to it here for now:-
http://www.vintage-radio.net/forum/s...d.php?t=137769

Re: 2N3055 Transistors.
 

Thanks for linking Techman. Sorry, hadn't seen your thread, or I'd have tagged on the end of it. Given the problems different versions of 2N3055 have obviously caused (and are still causing), why didn't they give them different type numbers! I originally posted to the Quad thread you mention, but it got diverted to a new thread as I didn't make the connection obvious enough.

Mike

Re: 2N3055 Transistors.
 

Regarding the actual case material I have a couple of these with aluminium cases, heatsink and cover.

Alan