Parasound DAC 800, help explaining alien diodes on circuit

[cortico]

Hi all, Recently I got a old Parasound DAC 800 for my elders system. It does sound pretty good, its defiantly an huge improvement, I think now I realize now below average my CD player sounds.

I have opened the DAC to check the circuit and component and I have found two diodes (1N4002) replacing the R316 (1K5 Ohm 1% 1/4) resistor. It appears to be connected between power switch and 4 pin of IC305 (TC74HC73P).

Could anyone help me to understand what they are supposed to do in the circuit?

Thanks a lot,

 

[mac mini]

If it is at the power switch its probably a clamp. When power switch is thrown it clamps the arc at the switch and shunts it to ground preventing an over voltage.

 

[SoNic67]

No, it's not that. It's connected between the +5V rail (for the Digital portion) and pin 4 to that IC Flip-Flop - 4 it is the supply for that IC. It's some kind of current limiter... Diodes in series drop some 1.2V, probably is what that resistor was doing initialy anyway.

BTW: Where did you get those schematics from, mine are scanned and 'divided' in two.