Help COLD OCL 300W Burn....

[Bee C.]

Please I've get burned the Final Transistor ( 2N3055 / MJ2955 ).....had 32V at output ( SPK ) whit input dc +/- 38V.....

It's an old stuff at my junked......i tried to rebuild but keep burn the C2,C4,C5 (47uf/50V)

I'M CONFUSED................

Please tell me what I've to do ?!

Many thank's

[Bee C.]

Hii dear I've make a mistake whit the pic....
Here The Pic.....

Thanks...

[anatech]

Hi Bee C.,
Please check the extension of your file name. There is a list of file types accepted. The size must be less than 100 KB.

The other method is to host the file and attach the url.

BTW, those outputs transistors are normaly only good for 60 VDC C-E. Therefore a maximum supply of + / - 30 VDC, 25 VDC to have some headroom. There were some that were supposed to be good for 100 VDC. I don't trust them.

-Chris

[destroyer X]

Than appear 2N3771 and 2N3773.

Those old RCA were excelent...i think you were too much young those days dear Anatech.

Then appeard the alluminium case Motorola units...those ones awfull!

We still make them in Brasil... a big company that started producing supplies to old computers using 2N3055 already produce them in this country. brand is SID

regards,

Carlos

[anatech]

Hi Carlos,

Those old RCA were excelent...i think you were too much young those days dear Anatech.

Thank you!

Unfortunately I do remember the original Lambda 2N3055 transistor.

It was spec'ed at 60 VDC C-E (I say that because many people look at the C-B voltage rating and it was often higher), 115W and an F-3dB of 19 KHz. It was originally designed as a power supply pass transistor and the low Ft was so it wouldn't oscillate when mounted on a heatsink with wire away from the PCB. Motorola manufactured the original I'll bet, and it was an accurate device under their name.

The others that followed should have had a different number as the specs were completely different. They weren't great parts but at least put up with higher voltages. This didn't make them a better part - in fact they were worse for the original application.

These days I hope one would use an MJ15003 and MJ15004 instead of the ancient 2N3055 and MJ2955. 2N3773 and 2N6609 were another good pair (this from memory! I need help!!!). 2N3771 was a low voltage, very high current device, 30 A was it? I think 2N3772 was a 20 A device (now I know I'm old!!).

Carlos, did I surprise you?

-Chris

[destroyer X]

fine that.... very good know how you have.

regards,

Carlos

[Juergen Knoop]

Originally posted by destroyer X

Then appeard the alluminium case Motorola units...those ones awfull!

Hi Carlos,
I still have some Motorola aluminium 3055.
Thought to build an ancient-style amplifier with them, sometimes...
Whats wrong with the aluminium types?
regards
Jürgen

[destroyer X]

Also they have no big weigth.... to me, they gave me the idea that were made with empty boxes...no weigth! ...ahahahahah.

Those ancient days, early days, my friends used to tell me... go down town and buy 2N3055 made by RCA only, do not buy those aluminium things Motorolla made!

I had many of those ones burned, the idea of fragille was associated, since those days, with those units.

Also some of them warped...and not a good heat contact with the heatsink.

Fragile leads too...if move them they broke inside the piece.

You may say they could be fake..... yes.....maybe because of that...it is possible, but i could find some samples, inside plastic bags, into television station technical place, Motorola guaranteed parts, sold to Ampex, with the same characteristics...i am not sure the ones i remember, as bad ones, if they were original or not.

regards,

Carlos

[Juergen Knoop]

thank you Carlos,
the RCAs have a good reputation, I've heard that before.
Hm, there is a BDX64 in my parts bin, aluminium Motorola too.
regards

[Bee C.]

To : anatech...

Thak's for ur solution I know I new here sorry for the pic mybe i have a bigger file than 100kb...but I currently see if the pic just about 84kb, I drawing whit Visio and safe the file in *.JPG and *.gif format......

BTW, those outputs transistors are normaly only good for 60 VDC C-E. Therefore a maximum supply of + / - 30 VDC, 25 VDC to have some headroom. There were some that were supposed to be good for 100 VDC. I don't trust them.

is there a simple explain for me....I'm a stupid in class....he..he....
if i give the rail/input about +/- 38Vdc it's supposed to be fine in mine ?! not get burn the Capsitor or the Transistor ?


To : Destroyer X

Than appear 2N3771 and 2N3773.

Than'ks for your solution...but...
in my country it's hard to find the Transistor......not cheap is the reason ?!
btw thank's guys......

I still get the Elco 47u/50V blew......

Thank's