Marantz CD63 & CD67 mods list

[Thomo]

Sounds to me like something is wrong with the resistors in the filter around the opamps.

Have you measured each resistor and compared its value against the schematic?

Lee.

[ian21]

Hello Lee
Yes all resistors check out ok there is just such a massive difference when testing between components and ground on the L & R channels, also the L side when checked any readings are not constant and rise steadily as if charging a cap. Its as if there is a 60k parallel path.. and i cant find it.
many thanks Ian

[ian21]

Also as an afterthought could it be something from the disabled hdam circuit as components in it are still detectable to ground??.... but now i'm guessing.

[avr300]

If it's disabled properly, it won't have any impact what so ever.

[ian21]

re the above sussed it- op amp knacked i guess coz r661 failed.

[Fidelity Audio]

good news then

Brent

[ian21]

oh yes... why do these things happen at weekends ? now to your site for some new uns.

[RCruz]

Originally posted by avr300
Correct, DGND and AGND newer meets. Separation point is the DAC.

Hi

I am seriously considering this mod that I believe must produce outstanding results.

My CD53 has LM4562NA opamps fed by a dedicated analog PSU.

Can I remove U205 and U206 and link here the Analog GND of the dedicated psu ?

Can this GND be left unconnected from the main PCB GND ?

(Must I will also isolate the output plugs so no connection will be left ?)

What are the pitfalls of such arrangement ?

Is it dangerous to isolate the GND circuits ? Can I expect some kind of dc offset ?

Regards

Ricardo

[ahiukka]

Hi.

My CD53 had a problem, first it worked all fine and in the next moment it started to pull drawer back and spin disc at very high rate. My first thought was that TCA0372 which operates the drawer and disc motor has come to its end. Well, after all I found out it was the that chip exactly(QM01), but it had burned also resistor R164.
Then I had trouble sourcing TCA0372, I began to look for substitute and after searching for a long time I found one which could substitute it; L2720. And it did!
This chip has some lower operating voltage range which has no meaning in this application because it still operates in specs. And slightly higher typical slew rate

So my point is that if someone else is having trouble sourcing TCA0372, you can substitute it with L2720.

-Antti

[RCruz]

Originally posted by RCruz


Hi

I am seriously considering this mod that I believe must produce outstanding results.

My CD53 has LM4562NA opamps fed by a dedicated analog PSU.

Can I remove U205 and U206 and link here the Analog GND of the dedicated psu ?

Can this GND be left unconnected from the main PCB GND ?

(Must I will also isolate the output plugs so no connection will be left ?)

What are the pitfalls of such arrangement ?

Is it dangerous to isolate the GND circuits ? Can I expect some kind of dc offset ?

Hi
After taking a good look at the schematic, I know it is pointless to remove U205 and U206.... C611 612 613 614 are connected in the inner line..... Of course I could cut the GND line that goes to U201 but........

One question remains:
Is it dangerous to isolate the GND circuits ? Can I expect some kind of dc offset ?

Anyone care to comment ?


Regards

Ricardo