Marantz CD63 & CD67 mods list

Jump to Latest
#13,881
humming bird

Hello gentlemen,

I've never encountered this and need help;
the second CD-53 I'm building ( http://atsh.free.fr/MarantzCDx3/ ) has a slight hum. I've noticed it when was playing an MFSL disc, low volume one wich requested me to turn up juice from headphone amp. Maybe it wa here with the 3 regs I've fitted.
It's a constat hum, play/pause/stop the same. Enough to make the player not usable in this state ( my very own CD-43 is dead silent in "no music" state ).

I guess it's on analog stage, music flows very nicely over the hum, so digital may perform well.

I have a cheap clock fed by the +V smothing cap prior to the 7812, then feeding clock signal through 33R and GND linked to player. Can the clock inject noise that the 7812 can't remove (cheap ON semi reg with thin heatsink) ? It's low freq. hum.

I also have an LT1086 CT5 at decoder analog and DAC Clock Ref. I can't see how on of them may hum both channel under clear music. A LM317 red Led'd for analog.

Any clue or things in mind to test?

Matthieu the humming bird.
 
Last edited:
#13,884
Hi Ricardo,
no it's not. I've removed all the stuff from the filter, it's like factory. No more slight hum when switched off. But still that annoying one when on. :'(
Will try to remove the regs, the LM317 one at DAC (oscillates whit the Muses? Faulty? A short?), if not then remove the 2x LT1086, and if still nothing good will put back the factory Xtal. Can the AudioGD clock pollute something? I've tried it with external PSU and it's the same...
Enough for today.
Matthieu
 
#13,886
Had a quick look at your pics...I think its going to be something simple, but not necessarily obvious. I cannot remember if the headphone output is picked-off after the o/put stage or not... but if it is:

From your new ouput opamps there is green wire - is that 0v return? If so, check that it returns close to the 0v the signal that enters the opamp is referenced to (ie, near the dac, maybe even where your 5v reg for the Dac is) - NOT the main PSU. The 'ground plane' in the 43/53/63 is an utter disgrace and cannot be relied upon 😉
 
#13,887
Hi Martin,

the headphones in mine is removed, (testing via a pocket amplifier on the RCAs),
the green lines are -12, the white & brown +12 (yep I'm short on wires!),
the thick black ones going from under each output to the PCB under the RCAs are the grounds, from a star under each output, then to the star at the former PCB's RCAs, wich is the same big ground line as DAC, all DAC before there was U219, now only DAC analog as I've removed it to check if any better (the same, beside that I wonder if it's best to remove it as it makes a better star but split the GND for a single IC).
Anyway, according to you it's wise to check 0V between the DAC's dedicated Reg and the output ground, will do tomorrow.

Thanks,
Matthieu
 
#13,888
Hi Matthieu,

Hum could be several things:

- ground loop, between two pieces of equipment, or internally on the board
- bad grounding internally, maybe you removed too much wire links?
- shield of interconnect disconnected?
- 50Hz ripple on the power supply, caused by large current draw or reversed electrolytic
- maybe oscillating regulator?

Ray
 
Last edited:
#13,889
Hi Ray,
I have a bad feeling about the clock, wonder why this is hot as hell, my Feals never get even warm, the AudioGD one is with a big heatsink and still hot. I have to find the Xtal and its caps... somewhere in the trash :'(
All inputs seams PS noises / Gnd related... I may put a big R to attenuate the output 😉

Matthieu, head in hum hands in...
 
#13,890
Well, nothing, nothing at all changed that hum, nor where and on what with what it's plugged, regs removed and such.
The only thing wich has not been touched is the output! I may move the ground of it, I'll do it Martin even if it's a long job here.

Beside that, at normal and even loud listening volumes it can't be heard, only at "full pot just to check" and if I hadn't done this I'll still be happy of the sound now. After all the opamp output may get rid of it and as it outputs at bit higer level... I have to say it's the first player in wich I start by fitting the DOS (noise friendly Ray IIRC) before doing a improvement on PSUs...

The only condition the hum goes away is when the player focuses, I can hear the lens goes up and down and the hum quickly fades and comes back at the same. I still have to regulate the drivers, maybe it will help...

Matthieu
 
Last edited:
#13,891
Strange. For all you know, it may have been there all the time but you just didn't notice it. With the muting gone, you can hear everything the player does when it's not playing. The hum changes when the player focuses, so it sounds like the problem is load related. A scope would be real handy to see if there's any excessive ripple on the supply lines. Also the internal ground could still be a cause. When the load currents do not run where they are supposed to, this can generate similar problems. You could do a quick check of the various supply voltages with a DMM, and see if they are not low or sagging. Also, check before the regulators, to see if the voltage doesn't fall below the minimum requirement = output voltage +2.0 to 2.5V. You may even try to measure residual ripple by using the AC function and see if you can detect any abnormal levels on the supplies.

Regards,

Ray
 
#13,897
Malefoda said:
All voltages OK, grounds of outputs to DAC's one, the same. Anyway, that's the very same hum as my phono stage and alsmot at the same (far away of music level) level! More than odd...
Click to expand...

disconnect all the input connections and see if it still does it!

Also, try disconnecting all your kit from the mains and adding back 1 at a time. I had a dodgy transformer in my CDP that was causing problems for my amp!!!😱
 
#13,899
Hello.

i'm back, just bought a 2nd cd67 mkII this week and would like to modify it slightly, i'm not planning to bring it as far as ny first heavily modified cd67se.

Mod's planned, opamps lm4562, disabling hdam, disabling output caps and transistors, muting circuit.

Just wondering if it is a good idea to re use the output caps's (c655/c658), elna silmic 220uF, around the opamps, replacing then the Elna 100uf (red) (C611/C614).

Can the Elna red's be used somewhere else as well.
 
You must log in or register to reply here.
Top Bottom