Problems adding Digital Out to Laserdisc player (LC78621 chip)

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Trying to add a digital output to a Laserdisc player. The datasheet for the chipset says pin 56 is DOUT. So I ran a wire from pin 56 to a TTL=>Coax circuit, however when I use a multimeter the voltage coming from the chip is only like 2.9V....shouldn't it be ~5.00V?

Needless to say I'm not getting any output.

I didn't do anything to the chip, as I don't see like a DOUT enable pin or anything.


Any ideas?
 
hi, you may try the following which I have done to my Onkyo LD player.

LC78621 75ohm coax CS8412/4
pin56-DOUT ---------------------------> pin9-RXP
common gnd ---------------------------> pin10-RXN
(find any gnd jumper next to LC78621)

I suppose you must have missed out the gnd :)
 
the voltage coming from the chip is only like 2.9V....shouldn't it be ~5.00V?
It would probably be something like that measured by a multimeter even if it was working so it really don't indicate anything.

Dout can be muted, details in the datasheet. The other issue could be how you've connected things, dout is made to drive a transformer direct again see the datasheet.
 
A 8 said:
Dout can be muted, details in the datasheet. The other issue could be how you've connected things, dout is made to drive a transformer direct again see the datasheet.

hi A8, do you mind sharing how could I disable the MUTE function in this chip....I know very little in digital world :(
Thanks in advance!
PS : I connected the DOUT to CS8414 via 1:1 Pulse Trans in my external DAC.
 
why do you need 74hc04 in the first place?
I connected the DOUT from LC78621 with coax cable directly to my digital receiver CS8414 via a 0.1uF wima mkp cap and 1:1 pulse trans (all in my DIY DAC). No problem with the output level.

coax
LC78621 pin56 (Dout) --------->0.1uF---->pulse trans--->cs8414
LC78612 gnd -------------------->DAC gnd
coax schield
 
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