Marantz MA9S2 choke input power supply

[panterka]

I only have these photos at my disposal. I'd love to see some photos, as I've been working on building MA9s2 tips myself for quite some time.

 

[Markw4]

Still haven't opened up one the ones here, but its getting closer to that time. Have some more dac work to do on the bench before I get one of the MA9S2 up there to take a look inside. They are very good amps, I am told maybe the 2nd best to ever come out of Japan.

 

[TonyTecson]

what is the best? no.1?

 

[phase]

Looking forward to seeing how that’s done, wad fascinated by this when I was putting together my quasi Goldmund clone.
Not sure if a line isolation transformer wouldn’t effectively do the same thing however.

 

[Markw4]

what is the best? no.1?

One possible contender was Luxman B1000F. At least it was more from around the time of MA9S2, as versus more recent. Maybe more on this subject later.

 

[Markw4]

Okay, finally got one opened up. Ground wire on the bus bar between the big caps goes almost straight down and attaches to the case baseplate:

 

[panterka]

Super.
What are the parameters of these capacitors, they are not in the services manual.

 

[Markw4]

 

[Veysel]

Hi.It writes C311 at their service manual.It is in series with R362 which is 10 ohms 3w .It is Zobel circuit to protect speakers from oscillation.

 

[Veysel]

Okay, finally got one opened up. Ground wire on the bus bar between the big caps goes almost straight down and attaches to the case baseplate:
View attachment 1168951

Dear Mark.Thank you for the photo.Could you also check the choke? We want to know DC resistance of the choke for building.

 

[Markw4]

~3.8R

 

[Veysel]

Thank you very much for your measurement.My friend also wants to know the VA rating of the Main transformer.I think it is not necessary but he wants to know it. I think It may be estimated by dimensions of the transformer too.

 

[Markw4]

If anything, the transformer may be a bit small for its use here. Rough dimensions are: 5-1/4" diameter, 3-3/4" high.

My comment: it may be better to use a core maybe one size larger than you think you need.

 

[Veysel]

I thought it was taller. Allright.Maybe we can use bigger core as it is easier to build.Could you also tell what is size of the choke approx?

 

[Markw4]

~2-1/2" high, ~3-1/2" diameter

Would also note that most of the electrolytics around the sound path are Silmic. A few others are Elna Certafine, or Nichicon KG(M). Beyond that I hope to close this thing up again pretty soon and put it back into hi-fi service. May open it up again sometime later, but can't say exactly when.

 

[Veysel]

Many thanks. It is appreciated if you can take as much photo as possible. Regards

 

[Veysel]

My friend also asks that Preamplifier has 2 Gnd connections.First input and secons one output of preamp.Which one connects to chasis

 

[Markw4]

There is an RF ground at the input:

DC ground must be via the output side.

EDIT: Well, maybe not. Looks like there are places for jumpers to ground (e.g. J505, J810, J811). Not sure where it connects. May depend on what was found to work best after the layout was tested.

 

[Veysel]

Could you also check the pcb pictures ? Thanks

 

[Markw4]

J503, J810, and J811 are all PCB mounting holes with metal screws and metal standoffs to a metal plate below the PCB. J505 appears to be a star point that connects to J503. For example: