Pro Audio Spectrum 16 PatchPanel - Schematic Development for Reproduction

[Trash80toHP_Mini]

Saw this: working toward it.

 

[smiba]

Here is the uncropped and non-resized version of the image on my wiki (https://retro.woof.tech/index.php?title=Apple_Macintosh_IIci):

View attachment DSCF1194.JPG

 

[demik]

As promised on the NUBUSPAS16-DB thread, here are my notes

Connector

Incomplete connector pinout, card side
 __________________________________
 \                                /
  \ 09 08 07 06 05 04 03 02 01   /
O  \ 18 17 16 15 14 13 12 11 10 /  O
    \ 26 25 24 23 22 21 20 19  /
     \________________________/

01 MIC L
02 MIC R
03 IN1 L (Crosstalk at -20dB ?!)
04 IN1 R
05 GND
06
07
08
09
10 IN2 L (Crosstalk at -20dB ?!)
11 IN2 R
12 IN3 L (Crosstalk at -20dB ?!)
13 IN3 R
14 GND (Digital)
15 +12V
16
17
18
19 IN4 L (Crosstalk at -20dB ?!)
20 IN4 R
21 OUT L !
22 OUT R !
23 GND (Joystick ?)
24
25
26

Other informations:
- only +12V found, no -12V (audio) or +5V (MIDI, Joystick). Either theses are generated on the patch panel, or the card is off spec.
- joystick seems to be doable without much component, but don't know enough about theses
- I got a bad crosstalk (-20 dB !) when using the left channels of line in 1-4
- the MIC input is actually a stereo line input. Some circuitry on the patch panel do the microphone preamp part and convert that to a stereo line signal

Test points

A few test points around op amps

IC #	Coupling capacitor	Signal
U15C	-	OUT R
U15C	-	OUT L
U15C	C509	IN4 L
U15C	C510	IN4 R
U13B	C505	IN3 L
U13B	C506	IN3 R
U13B	C507	IN2 L
U13B	C508	IN2 R
U12B	C503	IN1 L
U12B	C504	IN1 R
U12B	C501	MIC L
U12B	C502	MIC R

Other informations:

- U11B is likely a buffer op amp for the OPL
- Miximg op amps are gain 1, with 20kΩ + 20kΩ feedback
- Inline outputs resistors are 47Ω
- U15B is analog switch. For muting inputs ?

Misc

- No idea about the custom IC (Thunder) on the left. It's somewhere in the audio inputs paths and maybe line out as well
- Microphone preamp is maybe discrete, maybe using the custom IC
- headphones amp is discrete
- either it's generating -12V from the +12V or all pampas are braised and DC coupled (= bad). U5A or U6A ?
- I'm 90% sure, besides power, that the joystick lines are on on the card. Some go to the NE558 IC, which, was used with some PC Joysticks
- no idea about MIDI, but it probably need some opto couplers
- don't understand what the LF347s are for. They are duplicating a signal, that's sure. DC biaising ?

Hope it helps