Toshiba 2879 Red dot vs Non red dot. What's the difference ??

[unit_399]

A good friend who owns a surplus electronics parts place here got bunch of 2SC2879 Transistors marked TOSHIBA, and asked me to verify that they're the real thing. Said he'd give me a couple for my trouble, so I said Hell Yes. He sent me a pair of them ( non red dot).
I put together a test circuit based on the design in the Toshiba factory data sheet, and they seem to be the real deal. Sent them back to him.

He has both red dot and some non red dot, and asked which ones I want. What's the difference ?? Some one I know and trust told me that the red dots are later production and have a lower quality insulator between the die and the flange. Is this true ?? And is it the only difference ?? Anyone ??

- J.J. 399

 

[Shadetree Mechanic]

I believe you are correct. The red dots got a stigma for being different, and people took that to mean that they weren't as good. But if I had to choose, I would take the non red dots. Although either one is up to the task.

 

[Xracerx13]

RF Parts says:
The "Red Dot" on the transistor indicates that it is a high-quality, reliable, and durable component that meets strict manufacturing standards. The transistor is also lead-free and RoHS compliant, meaning it meets the European Union's Restriction of Hazardous Substances directive, which limits the use of certain hazardous materials in electronic and electrical equipment.
It is an improved version of the 2SC2879 transistor, featuring enhancements such as reduced on-resistance and improved linearity.

 

[unit_399]

I believe you are correct. The red dots got a stigma for being different, and people took that to mean that they weren't as good. But if I had to choose, I would take the non red dots. Although either one is up to the task.

I decided to go with the non-red dots. No disrespect to Xracerx13's post. After testing I know that the nondots are the real thing, but I wish he'd sent a red dot for me to test. Thanks guys for the replies.

- 399

 

[Xracerx13]

No disrespect taken. I would go with the non red dot also.
I had heard that the red dot ones were less sturdy as far as handling higher swr and over volting, but I happen to own an 8 pill with red dots, I just don't over volt them(keep them at 14v) and always make sure the swr is spot on before I use it.

 

[Eldorado828]

I decided to go with the non-red dots. No disrespect to Xracerx13's post. After testing I know that the nondots are the real thing, but I wish he'd sent a red dot for me to test. Thanks guys for the replies.

- 399

399, you struck a gold mine!
is he going to be putting any of those up for sale? If he is, a set of 4 would be nice to have.

Just asking for a friend

 

[unit_399]

399, you struck a gold mine!
is he going to be putting any of those up for sale? If he is, a set of 4 would be nice to have.

Just asking for a friend

Eldorado -
I'm sure he is going to sell them, but he usually sells in bulk not individual parts. I will ask him.
- J.J.

 

[nomadradio]

transistor is also lead-free

And even more important, beryllia-free. One of the banned substances in ROHS, along with lead. There is an insulating layer between the metal mounting foot and the underside of the white ceramic "pill" structure. On the original 2879, this layer is white. Made from beryllia ceramic, the most-efficient heat conductor that is also an electrical insulator. That metal mounting foot has no electrical connection to the insides of the transistor. The beryllia layer does that.

Just one problem. Beryllium, in this form and any others is banned from use in any consumer product in the EU, starting in 2007. The red dot is a redesign that uses aluminum nitride ceramic for this layer. It's gray, not white.

I have no proof that the gray ceramic reduces the safety margin when overdriving this transistor. Just a suspicion.

73

 

[unit_399]

I have no proof that the gray ceramic reduces the safety margin when overdriving this transistor. Just a suspicion.

73

I'm suspicious too.
Also, I was told by a tech, that I know and trust, that the the bottom of some of the red dot's flanges (the part that contacts the heat sink) have a slight high spot just below the center of the die. When replacing an RD2879, he always files the flange perfectly flat. He feels that the high spot may be the cause of some of the unexplained heat -related 2879 failures.
BTW . . . The flanges on the non-RDs that I tested for my friend were perfectly flat.

- 399

 

[Cable Guy]

I check mating surfaces with a flat edge or razors edge (hey yo!). A thick pane of glass, some fine grit sandpaper assortment and elbow grease can get you a mirror finish, perfectly flat. That's how I deck processors and heatsinks. A small drop of thermal compound will cover a large area of perfectly mated surfaces.

 

[unit_399]

Eldorado -
I'm sure he is going to sell them, but he usually sells in bulk not individual parts. I will ask him.
- J.J.

Asked and he said they are already sold. He said that he had people standing in line wanting to buy them.

J.J. 399

 

[Eldorado828]

Asked and he said they are already sold. He said that he had people standing in line wanting to buy them.

J.J. 399

I figured they'd disappear quick these days, I appreciate you asking.

Now as to the red dot Toshiba's, I've owned and still own (TS dx-399) amps with red dots and have never had an issue. They've worked great but of course they've never endured abuse either. I've never feared a failure as one does with hg or dei.

 

[Dr. Frankenstein]

If the ink of the Logo (Toshiba) on the pill smears with alcohol .....
it's a fake (one of BBI's videos explains it) ...... real 2SC2879s don't smear. But there were some good fakes with a Day Code of "6J" that were very good fakes that worked very well.

 

[SuperLid]

Nomadradio nailed it. The red dot was the designator of the replacement ROHS compatible part.