82E10 Dynamics Card Schematic questions

[drpat]

Hey all,

I'm working on a test jig for the E10 card and have 2 questions...

1) Pin number 23 is shown twice on the schematic... once connecting to the output of the -5V supply, and another place connecting to the compressor 'release' pot's wiper, which has a '0V' annotation next to it. Pretty confused as to how pin 23 could be at both -5V and 0V at the same time. I'm looking at Drawing No. T82010-71.

2) The "82E10 - DYNAMICS SECTION EDGE CONNECTOR" document notes that pin 45 is "Linked to 44 on motherboard". Is this an error? If 44 and 45 were actually linked together, there would be no difference in the 'fast' and 'slow' positions of the release switch.

[amillar]

Hi,
You're absolutely right, that diagram's been confusing since it was redrawn electronically in 1984, I very vaguely remember that the '0V' is a mistype of something that was on the old hand drawn circuit it was copied from. You'll see it got corrected and corrected over and over in '86 (I can't think now who 'BC' was who checked it), and I vaguely remember we just ran out of energy to get it changed again!

Anyway, as far as I know pin 23 and the release wiper pot are definitely at -5V, ignore that stray '0V' lettering.

 I think 45 should say 'linked to 48 on motherboard', so it's the same as the compress attack switch - making sure that nothing horrible happens as the switch is going between positions.

Cheers,
Andy

[drpat]

Thanks for the reply Andy, and for confirming my suspicions.

[gertius]

Hi all,
can someone with access to an SL611 channel please confirm that the channel compressor release pot wiper really connects to pin23 (-5V) of the dynamics card?
I´m not trying to doubt Andy here, but he writes that he very vaguely remembers that the 0V is a mistype, and I would just like to know for sure.

Comparing to other schematics (the 4k stereo channel, various clones) they all have it connected to 0V. If it´s really connected to -5V in the 4k then it would be a pretty big deal for me.

I have two custom racked 82e10 cards here, where it was implemented differently (one has the compressor release pot wiper connected to 0V and the other to pin23 = -5V), and there is definitely a difference in sound. I´d just like to get it correct & the same for both channels.

To my ears at -5V it increases the decay portion of the sound, sounds more forward and pushy, thicker, with more urgency, in a good way. The release pot doesn´t really do much anymore from fast to slow settings, comparing to it being connected to 0V (behaves as you would expect). But in general the sound is a bit fatter at -5V.

So if anyone could check this with a meter on an original SL611 channel I would be very grateful!

[Chris Simon]

It would seem the release pot wiper could connect to -5V or 0v, based on the setting of the jumper on the motherboard (see photo). In this case, 0V.

[amillar]

I´m not trying to doubt Andy here

Feel free to - it was a long time ago!

[amillar]

It would seem the release pot wiper could connect to -5V or 0v, based on the setting of the jumper on the motherboard (see photo). In this case, 0V.

That's interesting, and probably explains the confusion. I'd be pretty confident that this link was always set in the same position from at latest the start of 1984 until the end of production.

There's a challenge for anyone on this forum to find a 611 with this link set to the other position!!

Thanks for that,

Andy

[drpat]

Ah! I'll take the challenge, and check tomorrow. Never really noticed the jumper before.

[gertius]

Thanks Chris for the image!
Ah interesting, then it looks like there is no definiteve right or wrong, if both options were given.

Yes, like Andy I would also be very interested to find out if there are 611s with the jumper set to -5V.
As I wrote, after doing my own comparisons, I kind of prefer the sound at -5V. It´s not a huge difference, but there is one.

[gertius]

Because I was still really interested to get to the bottom of this, I also sent a mail to Bruce of the Desk Doctor.
He was so kind to reply, please let me quote him here:

The wiper of the release pot goes to a wire link on the mother board, and this has two possibilities - either to connect to pin 23 (-5V) or directly to 0V. It is always connected to 0V! I can’t remember when the error crept in on the diagram, but it has been wrong as far back as I can remember.

That settles it then, I will solder all release wipers of my cards to 0V.
Thanks everybody!