Seeking transistor information

[JohnLin]

My first post, so be gentle with me and thanks for letting me on board.

I'm trying to repair an amplifier for a friend. It has blown a bunch of transistors and being more of an RF engineer I'm not very good with audio transistor designations, so I seek some advice.

The transistor markings, and what I think the official numbers are:

Marking What I think it really is
A1696 2SA1694
C4467 2SC4467
C4793 2SC4793
A1837 2SA1837
B647 2SB647
H669 ???? It's a TO126-like case

Hopefully the first five are correct and I have found suitable source here in the UK for them on that basis. The one I am unsure about is marked H669 and is in a TO126-like case. No amount of Googling turns up anything reliable on this device. Could it be a 2SD669? I searched for the more likely 2SH669 and drew a blank. As the trannies are seriously dead, it's a bit hard to find out what polarity they are!

Any assistance with positive identification would be gratefully received.

 

[richie00boy]

Yes it could be 2SD669, just a 'compatible' part by another maker. This part is quite common in Japanese amps.

 

[JohnLin]

I should have said before that the amp is an Omnitronic P-1000, made in Germany. Quite an odd fault really, one of each of the three PNP and NPN output transistors has blown, together with both driver transistors and the 2SB647 and "H669" whatever they do. I have no circuit, so it's a bit of a hit and miss affair working out what everything does!

 

[richie00boy]

I would imagine the 669 is the VAS transistor unless it's thermally coupled to the output stage in which case it would be the bias transistor.

If just one of the output devices has gone I'd be tempted to replace the lot, especially if the drivers have gone. Otherwise you could be doing it all again in a months time.

 

[Mooly]

Hi, If it is any help 2SAxxx are PNP usually high frequency small signal, 2SBxxx PNP low frequency medium power , 2SCxxx NPN small signal high frequency and 2SDxxx are NPN low frequency medium and high power. THIS IS A GENERALISATION ONLY. Your H? 669 is almost certainly a 2SD669 (complement 2SB649) You might try MJE340 (npn) and MJE350 (pnp)
Regards Karl

 

[vhinze]

before you install the output transistors, you may wanna check the bias circuit. Otherwise you may blow them all again.

 

[eyoung]

hello all,

I've found www.datasheetcatalog.com a good place to find info on all manner of semiconductor current and obsolete. Even when google doesn't turn up a thing.


Elwood

 

[d3imlay]

When you have everything installed, use a 100 watt light bulb in series with the line to limit current. If there is still a problem the light bulb gets real bright and stays that way and you save all the new parts.

 

[JohnLin]

Thanks for the comments so far, folks - very helpful. I think I've concluded that the device marked H669 is an 2SD669 but I am rather surprised that its complementary device, the 2SB649 is not present. There is a 2SB647 which is in a TO92 (tall) case, which I suppose is a close electrical complement even though it's in a different package. Is it likely that the 2SA669 and 2SB647 have been used as a complementary pair?

It looks like I'll have to source a circuit diagram (schematic). Any ideas where to get one from? Once again Google has failed me!

 

[vhinze]

Screamatic

After you've finished casting about looking for a freebie, (no harm in that!), you may find one for about fifteen dollars at a website such as getmanuals.com

Sometimes this is the least agravating way to go.

Oops. I see getmanuals has gone tits up. I'll work on it and get back.

 

[vhinze]

You gotta tough one.

I'd try contacting the company at:


info@omnitronic.de