Repair SC3654 Issue 3 RC3654 Rev. A - Page 1
Forum section: electronics / repair

author: xan
author_rank: Regular Contributor
timestamp: December 12, 2018, 02:24:39 pm
content: Hi everyone!back again with a pair of soundcraft input modules coming from soundcraft 1998 rm-105 broadcast console, does anyone have some schematics for this board SC3654?Anyway let's start from the 1st one, symptom of malfunction for 1st one module is that XLR input signal is not routed to the main master bus connected trought 8289 connector, instead when cue switch it's selected the signal path seems working correctly on a test machine. Just tried to swap input etc... so could you suggest a start point to understand with components it's going to fail? op-amp? some resistor?(attached an old photo there is a resistor disconnected... keep in mind)Thank's for support

author: coromonadalix
author_rank: Super Contributor
timestamp: December 12, 2018, 11:31:29 pm
content: Te only thing i have is this, it came from an user manual, maybe you have this already ?My only guess would be to inject an 1khz 0db tone and follow its path with an scope or signal tracer ? and search all the ic's datasheets to help.

author: xan
author_rank: Regular Contributor
timestamp: December 14, 2018, 08:30:57 pm
content: unfortunatly i can't use a scope right now and an external psu to make more test, for now i just want to know the flow on the components order just logically, maybe i could detect witch area is defected, next attached some little info i made.Could you explain what are this 4 component (2x Fairchild CD4093BC Quad 2-Input NAND Schmitt Trigger / 2x MC14013BCP Dual Type D Flip Flop) used for and the order, location in the schematic ? is that Motorola use as logic ic right ? i'm a little bit confused...each of those maybe are used in combination for each channel line pgm (and aux) 1 motorola + 1 fairchild and the same only for cue line.... ?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 14, 2018, 09:58:19 pm
content: the 4093 and or the 4013 maybe used to have an correct logic and or logic level command signal to prevent some miss triggering and other things ....maybe they are associated with the logic circuitYou should enumerate all the ic's numbers on a paper and write down their functions, if you have an cd 4066 it could be used as an quadruple analog switch ...

author: xan
author_rank: Regular Contributor
timestamp: December 14, 2018, 11:28:46 pm
content: some more particular attached and a better full image (i don't noticed that the image on 1st post was so bad...) (two ic without type id on last photo are both motorola)

author: xan
author_rank: Regular Contributor
timestamp: December 15, 2018, 01:26:56 am
content: here is the table there are some transistor near that i will insert in the table later! are these function right?

author: coromonadalix
author_rank: Super Contributor
timestamp: December 15, 2018, 03:32:50 am
content: Because of the flash i have 2 ics i dont read correctlyNear your db15 connector named CN5 you have 4 mini relay ic's

author: xan
author_rank: Regular Contributor
timestamp: December 15, 2018, 02:21:16 pm
content: These 4 ic are for features and are Hamlin - HE3621A1210 but i think they are used only on db 15 connector?Updated table take a look on photo i can't find sheet for 2 transistor, what their function ?

author: xan
author_rank: Regular Contributor
timestamp: January 18, 2019, 02:03:24 pm
content: here a little update, for the signal path, take a look! (i made some error on ic and fn lists above... i update the table now) thank's

author: xan
author_rank: Regular Contributor
timestamp: January 25, 2019, 03:24:24 pm
content: Mmmm i'm a little bit confused about bus connector pinout....1)anyway could i use (Orange GND in photo - Audio Ground) as negative terminal for make some measurements and pickup some values ? or i need common or 0v pin (that i don't find for now)?(at last maybe 15 pin chassis pins on 1,7,14 according to reference manual?)2) One of the things that i don't really understand is why so many pin for I+ signal on 34 pin pcb connector ? anyone give some suggestion ?3) is the IC7 the last op-amp according to official manual to route signal to both pgm lines and aux lines ?4) is pgm line routed via IC9 analog mux/demux ? cause the IC7 output seems to be connected to IC9 on Y and Z pin across two resistor r57 and r58 below gain IC..?

author: xan
author_rank: Regular Contributor
timestamp: January 25, 2019, 03:42:54 pm
content: below more datasheet of IC...

author: xan
author_rank: Regular Contributor
timestamp: January 26, 2019, 04:01:48 pm
content: Guys i'm trying to power on the board ... using 16v and -16v 0.5 amp on each rails but nothing happens all leds are off... should i connect 0v ??but where ?