did I buy fake transistors?

[jpk]

I am trying to get original parts ready for Jeffs NAP250 clone and found his thread about BUV20s here. The BUV20s I received yesterday look exactly like the ones shown here, even the packaging looks exactly as on those pictures:

The BUV20s look a bit too new. The printing on one of them I could remove with aceton (but not with alcohol). It seems there are still new old stock ones available, and I will be happy to supply a link, but first I would like to make sure they are genuine. I also got some small signal transistors from the same source and BDY58s. Here some more pictures:

BUV20 and BDY58 opened with my lathe. The printing on the BDY58 cannot be removed with aceton. The BDY58 has 1mm pins (some show faint corrosion) and looks exactly like the ones on these pictures of an old NAP250 I found online:

Here a closeup of the BDY58 I opened:

My BUV20 has 1.48~1.5mm thick pins. I scratched off the white protection from one die with my finger nails:

The die looks a bit damaged because I was not very careful when sratching off the white rubber-like stuff:

And the small transistors:

The ZTX108C looks old and has the typical flat shape shape, the other TO92s haave the normal shape. The printing "PH" on the MPSA56 hints to Philips, or to made in the Philippines...? The legs of the BC239Cs look fresh and shiny, the other devices have old looking legs. Both types of BC239Cs have the middle leg bent backwards. I was told that one was made by Philips and the other by Siemens. Here are my measurements I took with a small cheap device tester:

BDY58: HFE = 11, VBE = 0.57
BUV20: HFE = 22, VBE = 0.53
MPSA56: HFE = 204, VBE = 0.73
ZTX108C: HFE = 650, VBE = 0.79
BC239C (first picture: Siemens?): HFE = 460, BVE = 0.75
BC239C (second picture: Philips?): HFE = 676, VBE = 0.75

What do you think about my parts?

 

[russel]

Nothing obvious, I thought the wires to the die looked a bit thin but if you are going to put two dies in then there will be some resistance needed for current balancing, it’s not really possible to test power transistors on a standard transistor tester as the currents are not high enough, although if you do get a high gain it does indicate a fake. Small signal ones unless you test for breakdown and frequency, capacitance etc, it’s an educated guess.

 

[davidsrsb]

I think genuine.
Nobody would fake with two big die
The can bases are meaty, fakes tend to be flimsy
The die are what you would expect, not some 3A part stuck in

 

[jpk]

Yeah, on most of the TO3s I got lower HFE readings. I am still a bit concerned about the fact that the BUV20s look so fresh and the printing came completely clean off with aceton. Also the white rubber-like stuff on the dies, ist that normal? Could it be that these were other strong but bad sounding and cheap two-die transistors and were relabeled as the more expensive BUV20s...?

 

[Vinny]

There will be very few inks used for this sort of application that will be acetone-proof. Meths/alcohol is not a good solvent for anything much at all, IPA even less so.

 

[Arkless Electronics]

Probably genuine but I'm a little wary of the ink.. They need to resist flux removing solvents etc.

Whilst I'd just about take Amstrad over Naim if I was struck by the need to make a NAP250 clone I would probably select alternative more modern semiconductors, hopefully a little better than the originals, and available from trusted suppliers such as RS. I NEVER buy components from ebay as I expect them to be fake. If a part has been obsolete for a decade and is pure unobtainium and suddenly it appears from some bloke in China on ebay in quantity and at an attractive price then what do think the provenance is likely to be?

 

[jpk]

There will be very few inks used for this sort of application that will be acetone-proof.

Would that mean even genuine TO3s can be wiped off with aceton...?

I would probably select alternative more modern semiconductors, hopefully a little better than the originals, and available from trusted suppliers

I know MJ15003 are used as replacements, but these have much slower speed ratings. What modern alternatives which can be used as a direct replacement for BDY58/BUV20 would you recommend?

 

[Vinny]

Would that mean even genuine TO3s can be wiped off with aceton...?

If they are ink, there would be a very good chance. What the binder in the ink is would determine how much/little elbow grease was needed in addition. I suppose they could be UV cured, which would make an ink tricky to shift, but probably not massively so.

@Arkless Electronics mentions resistance to liquids used for flux clean-up - when I was working in a capacitor factory, the common assumption was that a chlorinated solvent was routinely used, but at that time, they were also going aqueous because the usual solvents were ozone-destroyers. The usual chlorinated solvents - Triklone and Genklene (other brands available) are actually p-poor solvents in general terms, except that they are great degreasers, and presumably de-fluxers. At the end of the day, you can't use much aggressive to clean-up populated boards due to resistor colour coding and much besides, and the actual boards themselves. That is now over 20 years ago.

Plastic (probably mostly epoxy) encapsulated components, are near certainly marked using a laser - the resin formulation is designed to be so. Certainly all the capacitors that I knew, were. AVX house colour was a sort of mustard colour and when hit with a laser the encapsulant turned a medium red-brown - you can see that online easily enough - just look at AVX surface mount cap's. Your ones above look to be laser marked too.

 

[Arkless Electronics]

Would that mean even genuine TO3s can be wiped off with aceton...?



I know MJ15003 are used as replacements, but these have much slower speed ratings. What modern alternatives which can be used as a direct replacement for BDY58/BUV20 would you recommend?

The Naim designs are ancient and pretty slow anyway so speed of output devices is a moot point... MJ15003 and more modern still MJ21194 are much better transistors with far better linearity than those old ones.
If speeds your bag then you'll have to modify to use plastic cased transistors as the TO3 package is no longer used by the Japanese companies who make the really good output transistors. 4-5 times faster than BUV20 and with far better linearity and safe operating area devices are then available.

 

[Arkless Electronics]

If they are ink, there would be a very good chance. What the binder in the ink is would determine how much/little elbow grease was needed in addition. I suppose they could be UV cured, which would make an ink tricky to shift, but probably not massively so.

@Arkless Electronics mentions resistance to liquids used for flux clean-up - when I was working in a capacitor factory, the common assumption was that a chlorinated solvent was routinely used, but at that time, they were also going aqueous because the usual solvents were ozone-destroyers. The usual chlorinated solvents - Triklone and Genklene (other brands available) are actually p-poor solvents in general terms, except that they are great degreasers, and presumably de-fluxers. At the end of the day, you can't use much aggressive to clean-up populated boards due to resistor colour coding and much besides, and the actual boards themselves. That is now over 20 years ago.

Plastic (probably mostly epoxy) encapsulated components, are near certainly marked using a laser - the resin formulation is designed to be so. Certainly all the capacitors that I knew, were. AVX house colour was a sort of mustard colour and when hit with a laser the encapsulant turned a medium red-brown - you can see that online easily enough - just look at AVX surface mount cap's. Your ones above look to be laser marked too.

Yes I know.

 

[mansr]

At the end of the day, you can't use much aggressive to clean-up populated boards due to resistor colour coding and much besides, and the actual boards themselves.

Acetone is usually safe. The normal method of removing conformal coatings is to soak the entire board in the stuff.

 

[Vinny]

Acetone is usually safe. The normal method of removing conformal coatings is to soak the entire board in the stuff.

Having spent most of my 45-year working life in the chemical industry and nearly twenty of those working with endless different polymers and solvents, in LARGE quantities, amongst the last things that I'd use on a populated board, would be acetone, except fleetingly, assuming that you want the board to work after application.
Granted removal of conformal coatings is going to present a challenge, but there are probably other safer, if slower, methods - that rather depends on what the coatings are, chemically. Parylene is going to be tricky - if acetone is effective, it likely just softens/swells it.

 

[Jonathan]

the fake transistors i bought off ebay and installed in my qudos are working great so far

 

[mansr]

Having spent most of my 45-year working life in the chemical industry and nearly twenty of those working with endless different polymers and solvents, in LARGE quantities, amongst the last things that I'd use on a populated board, would be acetone, except fleetingly, assuming that you want the board to work after application.
Granted removal of conformal coatings is going to present a challenge, but there are probably other safer, if slower, methods - that rather depends on what the coatings are, chemically. Parylene is going to be tricky - if acetone is effective, it likely just softens/swells it.

I've never seen any ill effects from acetone on electronic components. Cases and other mechanical parts made of ABS plastic is another story.

 

[jpk]

the fake transistors i bought off ebay and installed in my qudos are working great so far

cool! But how can I make sure nothing damages in case a fake transistor blows? I would rather do some tests before using them...

The Naim designs are ancient and pretty slow anyway so speed of output devices is a moot point... MJ15003 and more modern still MJ21194 are much better transistors with far better linearity than those old ones.

I fitted my first boards with MJ15003s, they sound really nice:

Now I want to populate a board with parts closer to the original. I read that Julian Vereker considered speed more important than linearity regarding output devices, so I would be interested to know which transistors would match the speed of the original BDY58s but offer better linearity and sound!

 

[davidsrsb]

Speed vs linearity was a very different set of options when JV was in charge. Peak choice was when Sanken and Toshiba were making superb parts, unfortunately now long gone

 

[Arkless Electronics]

cool! But how can I make sure nothing damages in case a fake transistor blows? I would rather do some tests before using them...



I fitted my first boards with MJ15003s, they sound really nice:

Now I want to populate a board with parts closer to the original. I read that Julian Vereker considered speed more important than linearity regarding output devices, so I would be interested to know which transistors would match the speed of the original BDY58s but offer better linearity and sound!

I don't consider JV a competent engineer or Naim gear worth bothering with so all I can do is repeat that there are many plastic cased transistors, from Toshiba, Sanken, On etc that are vastly better in every way compared to the ancient BDY58.

 

[Pete MB&D]

Some information here.

https://sound-au.com/counterfeit.htm

Double die MJ1503

https://sound-au.com/fake/counterfeit-p1.htm

Pete

 

[Jonathan]

was being mostly facetious - there are no reasons to think the motorola stamped ones i bought off ebay are actually fake but everyone warned me not to get them there - they seem perfectly fine.

cool! But how can I make sure nothing damages in case a fake transistor blows? I would rather do some tests before using them...

 

[jpk]

I closed my opened ones (machined aluminum rings sealed with epoxy) so they are ready for some tests. But I still don't know how to make sure they wont blow in situ...