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

 

[smiba]

Would it be of help if I open up the patch panel I have and make some pictures of the PCB? I have a full set

 

[Unknown_K]

On the Pro Audio Spectrum 16 ISA card some of the custom chips are just relabeled parts from other manufacturers.

https://www.dosdays.co.uk/topics/retro_review_pas16_pt2.php

 

[demik]

Would it be of help if I open up the patch panel I have and make some pictures of the PCB? I have a full set

Not for me, but it may be interesting of other people show up. I wouldn't bother to open it if not needed as the plastic may break

On the Pro Audio Spectrum 16 ISA card some of the custom chips are just relabeled parts from other manufacturers.

https://www.dosdays.co.uk/topics/retro_review_pas16_pt2.php

Thanks. Nice article! Unfortunately the chip on the patch panel doesn't seem to exist on ISA cards