Help with a Darlington

[Rolnaashch]

Greetings!

I've got my hands on a Schneider Studio 80 compact system.
Honestly i made a lots of amplifiers with TDA ICs, but i only made solid state amps a long time now. So please, be gentle with me, i try to take out my best on this!

I found a darlington amp in it, and since it has the power supply in it also working, i decided to save the amp from it. But it has BDX33A - BDX34A pairs, and i searched over the internet countless times to find any schematics without any luck.

If anyone know any kind ot circuits or schematics, which uses these pairs, i would be really glad!

 

[indianajo]

What package BDX33/34?
For TO220 package TIP102/107 darlingtons, jiny just built an amp board. schematics in this thread: http://www.diyaudio.com/forums/solid-state/305917-class-ab-amp-using-tip102-seeking-critique-2.html
He has it working.

 

[mjf]

......bdx33(c)/34(c) are still available and i use them in an amp for experiments......

afaik telefunken amps had these in older designs (in the eighties or sowhwat)

 

[Rolnaashch]

Thank you very much all for the helps!

To be sure, and to share some oldschool vibes, here is an image

 

[Mooly]

Here is a typical darlington amp (using multiple pairs but you don't need to )

 

[Rolnaashch]

^^
Ah, so i am not strictly restricted to the exact type of BDX33/34, if i understand right, it's interchangeable!?
The integrated world smeared my knowledge badly about these things now, my loss...

 

[Mooly]

Yes, they are all pretty much generic type devices and should be pretty much interchangeable with few changes needed. The diagram I posted would ideally need the two diodes and R5 replacing with a traditional vbe multiplier (the little transistor on the heatsink in your photo) as that would allow accurate setting of bias current and also maintain that current with temperature variations.

 

[Rolnaashch]

Thanks again for the great help!
Is there any info on how strong are these darlingtons, i mean if there was any failure, (i've got it from a friend's dad) how quickly can get damaged those transistors? I really hope that i can save the amp part of this system. To be honest, everything seems to be working, only one major error is present, one of the fuse is die every time badly. I didn't had the time yet to analise further the problem's root, i just hope that it didn't damaged the amps main parts!

 

[Ketje]

As far as i remember those are rca transistors from around 1978.
Looks like there is an "A" after the type nr. Defines the max. voltage.
Here you can find a doc. https://4donline.ihs.com/images/Vip...7-1.pdf?hkey=EF798316E3902B6ED9A73243A3159BB0
Mona

 

[Rolnaashch]

As far as i remember those are rca transistors from around 1978.
Looks like there is an "A" after the type nr. Defines the max. voltage.
Here you can find a doc. https://4donline.ihs.com/images/Vip...7-1.pdf?hkey=EF798316E3902B6ED9A73243A3159BB0
Mona

Yes, that's the reason why i cannot find any circuits, schematics with these puppies

Thank you very much for the doc! ^^

 

[Puffin]

I had an old Creek 4040 with a Darlington pair that expired. Creek sent me a repair kit with new darlingtons and revised resistor circuit ( I think - it was a long time ago)

 

[Mooly]

I seem to remember some Philips audio products using similar-ish devices. We had a few failures but I suspect it was probably more down to customer abuse as much as anything.

In a modest amplifier for domestic use they should be fine.