S/PDIF output circuit - help fill in the blanks

[dingo99]

I recently picked up a Channel Master CM-7000 DTV converter box, which has an inactive S/PDIF coax output on the back. I'd like to try installing the missing circuitry to see if the output works, but I need a little help with the necessary component values.

Please see the attached photo. RA7 connects to the digital output from the decoder chip, and the lead going to RPR1 is the center conductor of the S/PDIF RCA jack.

Missing are 4 resistors, 3 capacitors, and 2 transistors. Using a DMM, I measured +1.65V @ RA7, +5V @ RD60, and +5V @ CD28/QD9. Any theories what the missing components should be?

[zandrax]

Re: S/PDIF output circuit - help fill in the blanks

I don't know and guessing is quite hard: these are acronyms you have to look in schematics, not values.
Usually electronic equipments follow a common project: the manifacturer design a very complete model then strips down whatever isn't necessary in order to fill the low-line market; low-line products have a different name with, I'll bet, a lower number or a shorter one. Find your 7000' big brother, the better equipped version that almost surely has a S/PDIF connection, and look for its schematics: you'll find your answer there.
As a start, your target may be a CM-8000DTV or a CM-7000DTVS (S as S/pdif): in short something as old as yours but with a "more important" name.

Zandrax

[gonzo0815]

Re: S/PDIF output circuit - help fill in the blanks

Lock at the data sheet, there is a circuit provided. usually it is not difficult to add it.