PCB mods?

[dimkasta]

I am currently working on the PSU of my SL1200 MK2, and while it is clear how an external transformer with quality rectifier, DC umbilical and a low noise reg can benefit our beloved turntable, we seem to more or less ignore the rest of the PCB.

My first thoughts was to replace the local decoupling caps C1 and C3

I used a 1500 Panasonic FC at 50V for C1 and a 47uF/25V Pansaonic FR for C3

The improvement was not small

Has anyone tried any other mods on the pcb?

I remember a few years back reading some stuff that would tinker with some thingies, but I could not find them again...

[Wakefield Turntables]

Who says we've forgot the PCB? I had mine recapped years ago and the benefits were very marked. No-one else on the techie band wagon has been bothered to explore this area of modification. :D

[worrasf]

Who says we've forgot the PCB? I had mine recapped years ago and the benefits were very marked. No-one else on the techie band wagon has been bothered to explore this area of modification. :D

:exactly: - see my post http://theartofsound.net/forum/showthread.php?12398-Vantage-Audio-Technics-SL-1210-PCB-upgrade-amp-PSU

Steve

[Andrei]

Who says we've forgot the PCB? I had mine recapped years ago and the benefits were very marked. No-one else on the techie band wagon has been bothered to explore this area of modification. :D

That reminds me - it is something I should look at. I take it you did not DIY? I'm sure it is not rocket surgery, but my natural clumsiness with a soldering iron may result in a FUBAR unless I get some help.

[dimkasta]

Well replacing each cap is one approach :)
But they are 38 and it is going to be tedious, and my guess is that not all of them will be that critical, not to mention that we might have to take ESR and/or ESL into consideration as well to make sure we create no problems...

There are only two marked as critical in the service manual. Those are C301 and C302 which are part of the pitch control. I would leave these alone.

I was looking for a more educated opinion on part replacement or modification :)
I understand it is offered as as a payed service, but I am more of a hands-on DIYer looking to "play" with my toys :)

[Wakefield Turntables]

I bypassed the pitch shift although tbh if I could remove it altogether from the pcb I would be happier.

[dimkasta]

Got any screenshots?

[Wakefield Turntables]

Nope! And tbh it would mean dismantling the whole 1210 and that's something I aint gonna do.

[dimkasta]

Fair enough :)

I found this reference


"Regarding the pitch control- you can remove and bypass it- unplug the connection of the pitch control wires/plugs and join the 2 center pins of the socket together."

Do you remember it requiring anything else?

[Wakefield Turntables]

Fair enough :)

I found this reference



Do you remember it requiring anything else?

Have a look on ths forum and read all the posts you will learn.

[dimkasta]

Cool thanks :)

I also ordered caps from mouser to start replacing. I will start with replacing the polyester and ceramic ones. I chose Polypropylene Vishay MKP1837 and 1841 for the polyesters, and Vishay MLCC for the ceramics

I will report my findings as I do

[dimkasta]

I isolated the pitch control yesterday. I did not notice any significant change in the sound.

Today I will also isolate the strobe and the stylus light, and remove any non-used boards from the chassis.

[dimkasta]

I found the mod I was talking about. Mike New also opened a thread about it but ended nowhere specifically.

The suggestion I found a couple of years ago was to add a 33K resistor and a 470n capacitor in parallel to C210, intending to reduce the power of the motor.

From my notes, I found that I noticed then an increase in clarity of highs and spatial information. I will try it again now that the TT is rather heavily modified and significantly better performing, and I will report back.

[Wakefield Turntables]

I isolated the pitch control yesterday. I did not notice any significant change in the sound.

Today I will also isolate the strobe and the stylus light, and remove any non-used boards from the chassis.

Why dont you just dismantle the strobe and cue light? TBH and in an ideal world I would like a PCB without any of these componets on.

[dimkasta]

Yes exactly what I have planned.

I am ordering the rest of the film and the electrolytics today.

Another option I am considering is to replace the zener supply of the 4011 chip with something quieter and further bypassing it with some film

And increasingC211 to 220nF and C210 to 550nF since I have seen some measurements that it significantly decreases wow and flutter by changing the motor time constants or something

[dimkasta]

Increasing C211 to 220nF and C210 to 550nF makes a very nice difference.

I also replaced all other caps in my pcb including electrolytics. From a first late night test at low volumes, there seems to be virtually zero sibilance in highs, and the mid-lows seem to be more present.

I have not replaced C301 and C302 since as it seems my board has MK5 values in it. Including the 3 extra ceramics (C217-219)
And I have no 6800pF or 33nF caps to use there.

[dimkasta]

Here is some porn.

12859

Not that a big of a change by the recapping...

[337alant]

Great job Dimkasta :eyebrows:

Alan

[Qwin]

When you remove the strobe lights don't forget to remove the switching transistor on the board. This will still be firing at 50Hz even when the LED's are disconected and is the probable cause of any noise introduced. It shunts the DC supply for the LED's to ground at a rate of 50 times a second causing them to momentarily dim at this frequency and hence the strobe effect.

[dimkasta]

From what I see in the schematic, the transistor is wired as a simple digital switch. By cutting the led wires you remove power from the collector of the transistor too, so basically it is not powered.

What is firing the 50Hz is the AN6680 chip, going from pin 11 to the transistor's base. But since there is no power on the collector, the transistor is still off.

To remove interference, we could perhaps cut leg 11 from AN6680, but I don t think it is going to be such a big deal.

[6L6]

I'm just using the stock power switch as the strobe on-off switch. I like it as it looks very stock.

[dimkasta]

Cool but I intend to remove all things sticking out of the chassis and covering it eventually with some veneer :)

By the way, I love having only the RPM led lit :) Looks so vintage with that rectangle led, but still very elegant at the same time...

[337alant]

Cool but I intend to remove all things sticking out of the chassis and covering it eventually with some veneer :)

By the way, I love having only the RPM led lit :) Looks so vintage with that rectangle led, but still very elegant at the same time...
I prefer green leds myself

Alan

[dimkasta]

Nah I always hated that kawasaki green :)

[337alant]

https://www.youtube.com/watch?v=3rRGtz96lv0&list=UUap5kkigjahy4ptRLMIwcRA

Green Calma :peace:

Alan