Gee, where to start? With so many mods and accessories for the SL 1200/1210, this may be a bit of a tired topic. However, I've just recently jumped on the bandwagon and have been thinking of offering some internal mounting brackets and maybe an external power supply chassis for diy-ers.
I will state that I'm with Landfall Systems and we are a commercial business. I'd like to start with some ideas and initial concepts, and will of course carry this over to our commercial thread if these ideas are product-worthy.
This all started with one of our customers asking for a simple armboard for a friend's SL1200 (but that's a topic for another day). I obviously had to pick up one or two of these turntables so I could tweak the armboard to fit just so. And now that I have a couple fairly well used M3D's, I might as well get them in shape.
Okay, so it seems the power supply is a popular place to start and a good upgrade can offer a lot of bang for the buck. Well, Pete Millett just happens to have a great filament regulator that seemed just about right for use in Technics power supply. Change the caps to the appropriate voltage (I used all 50v caps) and change the adjustment resistors, and voila, a clean 21 volts - adjustable. With a resistive load I measured 115 micro volts of AC noise. I haven't measured it in the turntable yet, but will get there eventually. I'll get my parts list together in case anyone is interested, and take some more measurements as I get the chance to.
Anyhow, on to the brackets. With the transformer relocated to an external chassis, it's old cavity is a great mounting place for the reg.
By the way, don't wire it as shown here. I didn't bother to look at the bottom of the little Technics regulator board. It's not wired straight from IC pins to solder pads. I have another picture with the wiring fixed. You'll also notice I only used 2 filter caps for twice the original capacitance. I may add more later.
So this is idea #1. We've made this bracket to fit where the transformer was and can make mounting holes for pretty much anything that will fit in the space. I'm putting this out there to see if anyone is interested.
You can also see the other mounting bracket that's where the power cord comes in and where the regulator IC mounts. More on this shortly.
I will state that I'm with Landfall Systems and we are a commercial business. I'd like to start with some ideas and initial concepts, and will of course carry this over to our commercial thread if these ideas are product-worthy.
This all started with one of our customers asking for a simple armboard for a friend's SL1200 (but that's a topic for another day). I obviously had to pick up one or two of these turntables so I could tweak the armboard to fit just so. And now that I have a couple fairly well used M3D's, I might as well get them in shape.
Okay, so it seems the power supply is a popular place to start and a good upgrade can offer a lot of bang for the buck. Well, Pete Millett just happens to have a great filament regulator that seemed just about right for use in Technics power supply. Change the caps to the appropriate voltage (I used all 50v caps) and change the adjustment resistors, and voila, a clean 21 volts - adjustable. With a resistive load I measured 115 micro volts of AC noise. I haven't measured it in the turntable yet, but will get there eventually. I'll get my parts list together in case anyone is interested, and take some more measurements as I get the chance to.
Anyhow, on to the brackets. With the transformer relocated to an external chassis, it's old cavity is a great mounting place for the reg.
By the way, don't wire it as shown here. I didn't bother to look at the bottom of the little Technics regulator board. It's not wired straight from IC pins to solder pads. I have another picture with the wiring fixed. You'll also notice I only used 2 filter caps for twice the original capacitance. I may add more later.
So this is idea #1. We've made this bracket to fit where the transformer was and can make mounting holes for pretty much anything that will fit in the space. I'm putting this out there to see if anyone is interested.
You can also see the other mounting bracket that's where the power cord comes in and where the regulator IC mounts. More on this shortly.
Attachments
And here's the other bracket. This one is about as big as we can make it to fill the space. We can make it smaller in any pattern that fits your needs, but would like to make at most just a few variants. You can see the original cover plate for the power cord entry on top of our bracket which is about as small as we can go with this one.
As shown, I mounted the regulator IC on top of the bracket. If you're going to do this, you should also apply heat transfer compound to the bottom where it mates to the original heatsink "platform." This will help to dissipate the regulator's heat into the chassis like the original design.
Again, don't wire the regulator IC like this, two of the wires need to cross. Unfortunately I took these pictures before I fixed the wiring and attached the power cord.
I don't have an immediate need for this bracket, but it seemed like a good place for one. Maybe you have a different regulator that could mount here or you need a plate to mount a detachable power cord connector.
Just trying to see if there's any interest.
Kind regards,
Dave
As shown, I mounted the regulator IC on top of the bracket. If you're going to do this, you should also apply heat transfer compound to the bottom where it mates to the original heatsink "platform." This will help to dissipate the regulator's heat into the chassis like the original design.
Again, don't wire the regulator IC like this, two of the wires need to cross. Unfortunately I took these pictures before I fixed the wiring and attached the power cord.
I don't have an immediate need for this bracket, but it seemed like a good place for one. Maybe you have a different regulator that could mount here or you need a plate to mount a detachable power cord connector.
Just trying to see if there's any interest.
Kind regards,
Dave
Attachments
Here are a couple of pictures showing how I wired the regulator into the main board. This also shows the correct wiring between Pete's board and the regulator IC.
Except for removing the factory regulator, I left the main board alone since only a few components are still in circuit. There's no adverse affect on the PS and only minimal current draw from these components. Makes it easier to return to original condition also
Out+ off Pete's regulator board is wired to J3 where the original 3-pin regulator was wired. Out- is wired to a handy hole w/solder pad that's real close to the gnd point off the factory rectifier. Some of the other potential ground points are connected to this one by small traces and I wanted to avoid overloading those traces. Besides, it's also convenient.
More on the regulator later.
Except for removing the factory regulator, I left the main board alone since only a few components are still in circuit. There's no adverse affect on the PS and only minimal current draw from these components. Makes it easier to return to original condition also
Out+ off Pete's regulator board is wired to J3 where the original 3-pin regulator was wired. Out- is wired to a handy hole w/solder pad that's real close to the gnd point off the factory rectifier. Some of the other potential ground points are connected to this one by small traces and I wanted to avoid overloading those traces. Besides, it's also convenient.
More on the regulator later.
Attachments
Yes, I used one of our cases. Below is a picture with the xfmr and factory circuit board installed. I'll get more pictures posted showing some layout options, hopefully this evening. I just got the chassis back from anodizing yesterday, so can also show it in the final form.
Pete Millett sells the PCB in his ebay store. He also has a full description with the board layout and schematic on his website. I copied his schematic and listed the component values I used and am checking with him to see if that's okay to post. I'll also get a BOM together for this higher voltage version.
Pete Millett sells the PCB in his ebay store. He also has a full description with the board layout and schematic on his website. I copied his schematic and listed the component values I used and am checking with him to see if that's okay to post. I'll also get a BOM together for this higher voltage version.
Attachments
Perfect. Part of the intent here is to use and provide off-the-shelf components so anyone can put this together. I also think Pete's board is a great solution in this application.
In case you need it, here's the link to the info Pete has posted.
Low Voltage Regulator
Also, we're close enough to Pete that we can get boards from him and ship along with anything you get from us. Should save a bit, especially on international shipments.
In case you need it, here's the link to the info Pete has posted.
Low Voltage Regulator
Also, we're close enough to Pete that we can get boards from him and ship along with anything you get from us. Should save a bit, especially on international shipments.
As mentioned earlier, here are some pictures of the external power supply chassis - or transformer chassis actually. The first picture shows the regulator board mounted in the chassis. I agree with the general consensus that the regulator should be in the TT chassis, so wouldn't necessarily do what's shown here. However, you could use one of the regulator boards for just the rectifier and mount that here. You could then use another board for the regulator and mount it in the TT. Fortunately, Pete sells these boards in pairs.
The second picture shows two terminal strips that could be mounted here for whatever else you want to do. We made all these holes on the CNC router based on how I wanted to put my PS together. We're open to other ideas and can change the holes for other layout options.
You can also see how the factory transformer interface board just fits in the chassis. I don't have a 110/220 version, so don't know how big that board is. From what I've seen, it looks a bit larger so we'd have to enlarge the case to fit or shift everything towards the other end.
The other pictures just show what the whole thing looks like and the last one how we machined the front and back for the connectors, pwr switch and light.
I'll shoot to get the schematics and BOM posted tomorrow.
The second picture shows two terminal strips that could be mounted here for whatever else you want to do. We made all these holes on the CNC router based on how I wanted to put my PS together. We're open to other ideas and can change the holes for other layout options.
You can also see how the factory transformer interface board just fits in the chassis. I don't have a 110/220 version, so don't know how big that board is. From what I've seen, it looks a bit larger so we'd have to enlarge the case to fit or shift everything towards the other end.
The other pictures just show what the whole thing looks like and the last one how we machined the front and back for the connectors, pwr switch and light.
I'll shoot to get the schematics and BOM posted tomorrow.
Attachments
I would wait until you're ready to tear it apart and make some mods. If you need different mounting holes for the board, we can make them pretty easily.
I have an Achromat as well and am thinking of machining finger holes to match the platter holes. I can use the CNC router to get them exactly opposite of each other and maintain balance. I'll try this with foamed PVC first, which seems almost exactly like the material they use. I'd like to know if the two holes make any noticeable difference in sound. I would imagine that any vibrations will be transmitted by the record into the rest of the mat, resulting in the same overall effect.
I have an Achromat as well and am thinking of machining finger holes to match the platter holes. I can use the CNC router to get them exactly opposite of each other and maintain balance. I'll try this with foamed PVC first, which seems almost exactly like the material they use. I'd like to know if the two holes make any noticeable difference in sound. I would imagine that any vibrations will be transmitted by the record into the rest of the mat, resulting in the same overall effect.
Hi,
Yes, popular it seems, and there are of course claims of gross improvements, but is there any proof to the pudding?
The original Technics regulator is not bad at all and certainly sufficient for this task.
If You want to improve matters, just add a simple 3-pin Regulator ahead.
The original transformer offers more than enough headroom voltage.
Or You could replace the original trafo, that is of truely low quality, by a 24V SMPS which fits into the plinth.
No need for a external casing with the same old trafo and fugly wiring.
There are for sure other points where one could sensibly tune and tweak a Technics for good.
jauu
Calvin
Yes, popular it seems, and there are of course claims of gross improvements, but is there any proof to the pudding?
The original Technics regulator is not bad at all and certainly sufficient for this task.
If You want to improve matters, just add a simple 3-pin Regulator ahead.
The original transformer offers more than enough headroom voltage.
Or You could replace the original trafo, that is of truely low quality, by a 24V SMPS which fits into the plinth.
No need for a external casing with the same old trafo and fugly wiring.
There are for sure other points where one could sensibly tune and tweak a Technics for good.
jauu
Calvin
I'm going off DIY'ers claims of improvement as evidence that there's really something to gain. However, I have two nearly identical SL-1200's that I'll be using for comparison.
The main reasons for moving the transformer to an external chassis are to get the EM fields and the mechanical vibrations generated by the xfmr away from the cartridge. Even though the factory unit has a mu metal shield and rubber mounts, this should help. Personally, I'm using the factory xfmr because it is adequate and it's free.
If you have some Technics tweaks, feel free to post a link. I'd like to check them out.
The main reasons for moving the transformer to an external chassis are to get the EM fields and the mechanical vibrations generated by the xfmr away from the cartridge. Even though the factory unit has a mu metal shield and rubber mounts, this should help. Personally, I'm using the factory xfmr because it is adequate and it's free.
If you have some Technics tweaks, feel free to post a link. I'd like to check them out.
Below is a 1:1 pdf of my chassis layout on an 8.5" x 11" sheet, should print just fine on A4 also. This has the holes and outlines for the factory transformer, 110 v interface board and Pete's regulator board. You can use this to help layout your own chassis. Might be a little easier than trying to mark holes using the actual parts.
And the regulator schematics...
The first is for the rectifier and regulator all on Pete's board to be mounting inside the plinth. I basically copied Pete's original schematic and changed the component values to show what I used. Posted with Pete's permission of course.
The second one shows how I'd build two boards with the rectifier in the power supply chassis and the regulator in the plinth. This obviously keeps all AC away from the turntable and is possibly better. Since I didn't build mine like this, I used shielded cable which is grounded at the external PS chassis. I may change to two boards later, or may not
You can see there are 7 places on the board for filter caps: C1, C2, C4, C5, C6, C7 and C10. I only have 2 of these in mine currently which is still more than the factory configuration of 470 uF. As I mentioned earlier, AC ripple on the output is very low across a resistive load. I still need to measure it in place and with the turntable running. Though I did measure the DC voltage under load and it's a rock steady 21V at both 33 and 45 RPM.
I've included a BOM below as well. I bought everything from Mouser here in TX since I can order one day and have it the next. These are all fairly common parts that you should be able to get from most vendors. If all else fails, you can look up the parts for size and pin spacing info. Feel free to ask if you can't find what you need on a specific part.
I used a 6.19K resistor for the bleeder because that's what I had. Off the rectifier I get 35 V, so this works fine. I've listed 6K - 9K for this resistor. If your rectified DC is closer to 40V, you might want to use something closer to 9K.
In the BOM I show Vishay RN55 resistors. These are the same as the CMF55 series (see Vishay's spec sheets) only with Military labeling and specs. Specs for the CMF55 show 1/2 W at 70 C vs. 1/8 W for the RN55. With the 6.19K at 35 V, the resistor is dissipating about 0.2W so in a non-Mil Spec application we're good.
If you see a better way to do any of this or have anything to add, please feel free to chime in.
The first is for the rectifier and regulator all on Pete's board to be mounting inside the plinth. I basically copied Pete's original schematic and changed the component values to show what I used. Posted with Pete's permission of course.
The second one shows how I'd build two boards with the rectifier in the power supply chassis and the regulator in the plinth. This obviously keeps all AC away from the turntable and is possibly better. Since I didn't build mine like this, I used shielded cable which is grounded at the external PS chassis. I may change to two boards later, or may not
You can see there are 7 places on the board for filter caps: C1, C2, C4, C5, C6, C7 and C10. I only have 2 of these in mine currently which is still more than the factory configuration of 470 uF. As I mentioned earlier, AC ripple on the output is very low across a resistive load. I still need to measure it in place and with the turntable running. Though I did measure the DC voltage under load and it's a rock steady 21V at both 33 and 45 RPM.
I've included a BOM below as well. I bought everything from Mouser here in TX since I can order one day and have it the next. These are all fairly common parts that you should be able to get from most vendors. If all else fails, you can look up the parts for size and pin spacing info. Feel free to ask if you can't find what you need on a specific part.
I used a 6.19K resistor for the bleeder because that's what I had. Off the rectifier I get 35 V, so this works fine. I've listed 6K - 9K for this resistor. If your rectified DC is closer to 40V, you might want to use something closer to 9K.
In the BOM I show Vishay RN55 resistors. These are the same as the CMF55 series (see Vishay's spec sheets) only with Military labeling and specs. Specs for the CMF55 show 1/2 W at 70 C vs. 1/8 W for the RN55. With the 6.19K at 35 V, the resistor is dissipating about 0.2W so in a non-Mil Spec application we're good.
If you see a better way to do any of this or have anything to add, please feel free to chime in.
Well, I went to populate the rest of the filter caps in the regulator board and realized I had installed the 470 uF caps instead of the 330 like I listed in the bill-of-materials. New BOM is attached listing both. Anything similar will work, but to fit you'll need caps with a 10mm case diameter and 5mm pin spacing.
Wondering what the current draw is off the regulator, I hooked an ammeter in line and took some measurements. These are as follows.
- Strobe LED's off, pop-up lamp off, motor off: 168 mA
- Strobe LED's off, pop-up lamp off, motor running: 174-178 mA
- Strobe LED's on, pop-up lamp off, motor off: 182 mA
- Strobe LED's off, pop-up lamp on, motor off: 209 mA
- Strobe on, pop-up on, motor off: 224 mA
- Strobe on, pop-up on, motor running: 231-235 mA
- Peak draw with strobe on, pop-up on and motor starting or stopping: 665 mA
I was very surprised to see the motor drawing only about 10 mA when it's running. The fluctuation when running is continuous and is obviously the compensation to hold the platter speed constant.
I replaced the pop-up lamp with a 3.3V regulator and an LED. Since the regulator gets pretty hot, I stuck it in a heatsink which I glued to the plinth with some Loctite thermal adhesive. The Loctite is what we use on our heatsink assemblies and it's come in handy for several other things - I'll go look up the part numbers if anyone is interested. Anyhow, current draw with the LED is undoubtedly different than with the factory light bulb.
The strobe LED's I hooked to what used to be the power switch. This is just disconnecting the LED's from the circuit and is not disabling the oscillator circuit or the transistor that drives them. Maybe it helps reduce noise during those critical listening sessions, but I did it primarily just to turn the lights off and to make use of the otherwise abandoned switch.
Wondering what the current draw is off the regulator, I hooked an ammeter in line and took some measurements. These are as follows.
- Strobe LED's off, pop-up lamp off, motor off: 168 mA
- Strobe LED's off, pop-up lamp off, motor running: 174-178 mA
- Strobe LED's on, pop-up lamp off, motor off: 182 mA
- Strobe LED's off, pop-up lamp on, motor off: 209 mA
- Strobe on, pop-up on, motor off: 224 mA
- Strobe on, pop-up on, motor running: 231-235 mA
- Peak draw with strobe on, pop-up on and motor starting or stopping: 665 mA
I was very surprised to see the motor drawing only about 10 mA when it's running. The fluctuation when running is continuous and is obviously the compensation to hold the platter speed constant.
I replaced the pop-up lamp with a 3.3V regulator and an LED. Since the regulator gets pretty hot, I stuck it in a heatsink which I glued to the plinth with some Loctite thermal adhesive. The Loctite is what we use on our heatsink assemblies and it's come in handy for several other things - I'll go look up the part numbers if anyone is interested. Anyhow, current draw with the LED is undoubtedly different than with the factory light bulb.
The strobe LED's I hooked to what used to be the power switch. This is just disconnecting the LED's from the circuit and is not disabling the oscillator circuit or the transistor that drives them. Maybe it helps reduce noise during those critical listening sessions, but I did it primarily just to turn the lights off and to make use of the otherwise abandoned switch.
Hi,
just because of interest.
Is there an explanation why there´s a current compensated choke behind the regulator and not in front of it?
As it is one of the most prominent aims to get a as low and constant regulator output impedance over a as wide bandwidth as possible, the position of the choke seems a bit odd on first glance.
It spoils regulation.
Even if the differential mode impedance is lower over most of the bandwidth, the stray inductance (not specified here) will give a rising impedance response.
As the copper resistance is low a high Q tank circuit may be formed together with the following capacitance.
If that happensthe idea of the regulator is caricatured.
jauu
Calvin
just because of interest.
Is there an explanation why there´s a current compensated choke behind the regulator and not in front of it?
As it is one of the most prominent aims to get a as low and constant regulator output impedance over a as wide bandwidth as possible, the position of the choke seems a bit odd on first glance.
It spoils regulation.
Even if the differential mode impedance is lower over most of the bandwidth, the stray inductance (not specified here) will give a rising impedance response.
As the copper resistance is low a high Q tank circuit may be formed together with the following capacitance.
If that happensthe idea of the regulator is caricatured.
jauu
Calvin
Yes, of course. Please try the following -
Place needle on a record with the platter stationary.
Increase volume until you hear 60Hz (or 50Hz) in your speakers. This is fairly easy with the transformer inside the plinth.
Remove the transformer from the plinth, and this test becomes almost impossible. Making the AC part of the PSU outboard to the TT is just a added bonus.
If you have ever seen one close, you will find that not true at all. It's EI - which is good for not coupling AC mains noise into the circuit, mounted on a rubber cradle with no screws on the transformer, mounted inside a mu-metal shield, and that shield has rubber isolation feet... It's of incredible quality.
But no matter how much isolation is applied, it will still vibrate, as all transformer do, and the cartridge is more than sensitive enough to pick it up and add that noise to the playback chain.
Removing the transformer from the plinth and placing it in an external case is 85% of the advantage. It is very necessary.
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