Author Topic: SSL 4k dynamics card, what part is this?  (Read 3009 times)

gertius

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SSL 4k dynamics card, what part is this?
« on: December 13, 2018, 06:52:55 PM »
Hi guys,
can you please help me identify a part of the SSL 82e10 dynamics board?
It is in the position D27, according to the schematic it´s an AAZ17 Germanium diode.
Problem is, all the AAZ17 I find in the net look really different to this part.
They either are totally black, with AAZ17 printed on, or are a transparent glass cylinder.
Is this also an AAZ17 or some sort of replacement type?

I am attaching pics of the part, zoomed in, and of the whole card (part is on top right).

Thanks!
Christian

pascal.verdet

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Re: SSL 4k dynamics card, what part is this?
« Reply #1 on: December 14, 2018, 08:24:14 AM »
Germanium diode AAZ 17 - 75V 140mA 300NS 10 - 0.85

gertius

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Re: SSL 4k dynamics card, what part is this?
« Reply #2 on: December 14, 2018, 10:41:22 AM »
Hi Pascal,
thanks for your reply!
Do you know the part (by the looks) or did you get it from the schematic?
My question boils down to this: is my pictured part really an AAZ17 or maybe something else?
Did you see it in that optical appearance on other SSL boards?

Thanks!
Christian

walrus

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Re: SSL 4k dynamics card, what part is this?
« Reply #3 on: December 14, 2018, 01:01:52 PM »
Of the 3 spare 10 cards I have, one has a diode marked AAZ17, one has the diode looking like yours and measures the same as the first one.
The third card doesn't have the diode at all!
Kevin.

gertius

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Re: SSL 4k dynamics card, what part is this?
« Reply #4 on: December 14, 2018, 01:56:09 PM »
This helps me a lot. Thanks Kevin!

amillar

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Re: SSL 4k dynamics card, what part is this?
« Reply #5 on: December 14, 2018, 02:14:54 PM »
The type of that diode is important, not the voltage / current rating so much as the "curve" the diode gives to the dynamics response. It wasn't fitted to the very early 10 cards, it was added sometime around 1980? It was certainly there by 1984.

So the main thing is that it needs to be a germanium diode, not a schottky. That said, I think on the 9k I did use a schottky because we couldn't buy germaniums any more.

They may well have changed case style, and I vaguely remember I changed the type of diode in the late 80s because the AAZ17s became obsolete?? We wouldn't have bothered updating the circuit diagram for that. 

Basically if you need to replace them try to find AAZ17s if you can.


The glass case was a PITA. If you try adjusting up the dynamics card presets under (for example) fluorescent lights you find it behaves very strangely, those diodes are light sensitive. I remember trying to set up a 4k with the 611s on extender cards inside a BBC mobile studio (one of only two studio installations we ever did ourselves) and it took me ages to work out why when I put them back in the desk the dynamics were out of cal again...

Cheers,

Andy

EDIT: I've just found my 9k circuits, and I did use an AAZ17. So I guess should be that in all 10 cards as well. But different manufacturers may well have used different case styles, we really struggled to buy these so would have changed manufacturer occasionally.
« Last Edit: December 14, 2018, 02:22:18 PM by amillar »
co-designer and project manager G series analogue 1987
channel strip designer J series 1992-93
design "caretaker" 4000/6000 1985-93
analogue team leader ARC/Bertha 1988-92

pascal.verdet

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Re: SSL 4k dynamics card, what part is this?
« Reply #6 on: December 14, 2018, 03:48:48 PM »
Seems like the AAZ17 is a relatively long recovery (350nS) diode.  The only sub I could find was AAZ15.

gertius

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Re: SSL 4k dynamics card, what part is this?
« Reply #7 on: December 14, 2018, 03:53:46 PM »
Thank you Andy and Pascal for your replies!

Andy, the background info you´ve given seems to be spot on.
I have in the meantime compared AAZ17 vs AA133 (those I have in another card), and the sound output is the same.
So it really seems that only the type of diode is important, but not so much the voltage/current rating.

Cheers!

pascal.verdet

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amillar

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Re: SSL 4k dynamics card, what part is this?
« Reply #9 on: December 14, 2018, 10:08:47 PM »
Seems like the AAZ17 is a relatively long recovery (350nS) diode.  The only sub I could find was AAZ15.

I can't see that causing a problem! Many thanks for the suggestion.

(And Hi Pascal, nice to hear from you again!  :) )
co-designer and project manager G series analogue 1987
channel strip designer J series 1992-93
design "caretaker" 4000/6000 1985-93
analogue team leader ARC/Bertha 1988-92

Showcase

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Re: SSL 4k dynamics card, what part is this?
« Reply #10 on: December 25, 2018, 08:35:14 PM »