Technics SL-1200 DC Power Supply

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#521
I need your help with my 1200 power supply conversion!
I'd like to go to a switcher ps as follows:
1. Remove original transformer and 3 leg regulator
2. Install a 20w medical grade SMPS brick like THIS ( www.cui.com/product/resource/vms-20.pdf ) CUI VMS-20-24
followed by A2CMx
3. connect into Ground and J3 point in the motherboard

So my question to you:
1. Is this ok? What do you guys think about this? Will I need more than 20w brick?
2. Can I leave all original stuff on the mother board and just "tap" into J3 point on the board?


I'm trying to keep it stock without desoldering a lot of parts... So I can revert, if the above does not work well.
thanks....
 
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#525
J3 is the correct place to deliver the output of your new power supply. Adding the DC filter looks like a nice addition. The total power consumption of the SL-1200 is somewhere in the neighborhood of 200mA, so a 24w psu will be plenty.

If in doubt about power supply location, you can measure J3 on your own to confirm. JUST DO NOT PUSH STAR/STOP WITHOUT THE PLATTER IN PLACE! Doing so will kill the motor drive.
 
#528
And the problem with a SMPS is that it may radiate EMI/RFI into your cartridge. I don't know if the particulars associated with "full medical safety approvals" include data or performance characteristics concerning noise. The word "safety" might refer to short circuit protections as well as how it handles overload conditions.

A number of SMPS that I've played with have spewed EMI/RFI noise into the air and into the household AC mains.
 
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#529
Hi,

I suggested the use of an SMPS alot earlier in this thread.
There's nothing to worry about .... it'll be dead silent.
But I would either leave the regulator in place, or replace it by a modern 'fast' regulator designed for switcher supply post regulation.
And I would certainly add a input filter to the SMPS, and maybe even add a post filter ... keep wiring short and layout compact.
With a decent SMPS there is no need to put the supply external.
The term 'medical' applies to supplies with very low leakage, typically by omitting with the PE connector and. the associated Y2-caps.
Apart from that there's no difference in overload and short handling.

jauu
Calvin
 
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#530
So, this seems to point to the need for choosing your SMPS carefully, purchasing from a reputable manufacturer, and testing the unit you plan to use before going through the work of actually installing it. Testing should be easy, just power it up and bring it close to your cartridge while you have an amplifier powered up or a scope connected to make sure it doesn't introduce unwanted noise.
 
#532
First time poster (loooong time lurker) with a quick question.

But first a sincere thank you to 6L6. Between this thread and “building the Pearl 2” thread I’ve spent nearly 6 years poring over your posts and referencing your pictures. You’re a legend, mate!

Ok - the issue at hand. I am measuring 41.6vdc out of my PSU. But I am only getting 19.6v when I have it hooked up to the regulator. Is this close enough? Or is there an easy way to figure what is causing it to be about a volt low?

I did a point to point assembly with generous tape and heat shrink just like 6L6. I tried following the schematic he drew up as closely as possible. I used a 1N4007 instead of a 1n4002. I used two Zener diodes (an 11 and an 8.2 in series). Any ideas what would cause me to be under 20v?

Thanks in advance!
 
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#534
RickRay said:
Add those two together, what do you get? 19.2, means the zeners are not dead on. A 10 and an 11 would give you the 21 your looking for.
Click to expand...

Thanks for the response. I was under the impression that the output from the LM317 would be the sum of the Zeners +1.25v. That is why 6L6 calls out 19.25v of zeners on his original hand drawn schematic. I do have two 11v zeners I could series.
 
#536
cbueche said:
Got the 2-wire cabvling done, the regulator installed, and the internals tidied-up. Answering my own question about consumption and regulator dissipation: with my PSU and the KAB regulator, the PSU output voltage drops to about 32V, so the dissipation is in the 2W range, all good for the LM317P and the huge heat-sink that the chassis constitutes. It's now playing Dire Straits Water of Love, and yes I notice a difference in darkness between now and before, although this is not a real A/B test. It takes out the main source of noise from the turntable chassis and that's the goal, it can only be better. No picture yet as the final case hasn't arrived. I need to figure if I pay Schaeffer (aka Frontpanelexpress) to make me a nice panel with the logo, might makes sense as this turntable will be mine for many more years.
P.S. 3 PCB remaining for interested.
Click to expand...
Hi Charles, Do you have PCB for sell?
 
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