Electrocompaniet AW65 Help request

[rollo22]

Hello all
Could anyone, please, give me some clarity on this issue ?

The schematics is for the Input Stage only of the AW65.

Power Supply is -+47Volts.

The offset measured at OUT drifts with temperature from - 10Volts to +3Volt after 2 minutes.

The temp of Q8-Q9 reaches 63ºC.

The calculated current on Q9 (Vce 36V) collector is 23mA for a dissipation of 800 mW.

Does it all make sense ?

I have doubts that the offset should drift so much.

I heard that Electrocompaniet amps dissipate a lot of heat, maybe that's why the fault on this amp destroyed so many transistors, they work at such Hi Temp.

Many Thanks

Rollo

 

[Andypairo]

Hi Rollo,
IIRC the AW65 has a separate protection-servo board.

Do you have a photo of your unit?
I once have fixed a wannabe-AW65 (but more likely a mixup between different EC models)

Ciao

Andrea

 

[rollo22]

Here it is
Please tell me all the dilfferences you see.
I think the big blue caps are not original.
There are some Transistors missing for now.
Ciao

 

[Andypairo]

Hi,
you can check the one I have here http://www.diyaudio.com/forums/showthread.php?s=&threadid=25386&perpage=10&highlight=&pagenumber=2

Btw you seem to miss the protection / servo boards... the photos I made show that these are marked "AW-65"... let me guess... does your amp come from a "official" EC repairer in Meda?

If so both you and my friend (the owner of the amp) have ben screwed by the same guy....

Cheers

Andrea

 

[darkfenriz]

Q8 should be NPN

 

[rollo22]

Hi
there is a marking AW behind the finals and pp on lower right.

No, I bought it from a guy in Switzerland.

Have you got a photo of the servo board with connections to the amp board ?
even if you made it.

Thanks

Rollo

 

[rollo22]

and this

 

[jacco vermeulen]

I suppose the original MT200 Toshiba output devices are blown too ?
The original electrolytics were Roedersteins, these looke like Philips or Sprague.

 

[rollo22]

Yes it is the same as Q9, my mistake (the model is the same though).

as and finally...

 

[rollo22]

Here's the right drawing, I hope...

Rollo

 

[rollo22]

Well, the caps are Filmcap 15000UF 40 V dated 1986 (strange, old as amp ?)

Power supply DC measured -+47 VDD and -+37V VCC

the finals are SK 2SA1694/2SC4467 some gone some good.

I will use Toshiba 2SA1943/2SC5200.

thanks