An interesting tweak from Kevin at KAB USA...

[Marco]

Guys, I received an email the other day from Kevin, outlining the fact that during his experiments with the Technics, he found what he considered to be a flaw in the current grounding within the T/T. Here’s what he wrote:


Wanted to mention, that I have been working up a 16rpm mod for the 1200, basically a half speed mod. So that is 16.66 and 22.5 in addition to the stock 2 speeds. This is for half speed mastering of really warped discs, and of course, talking story books, bible readings and sermons all of which were issued at 16 rpm.

This will be followed by a half speed mod with 50% variable speed. That’s really for DJ's.

In doing this mod it revealed an interesting flaw in the ground current distribution scheme. And that is really what I was contacting you about. You can improve the performance of the main control chip IC201 by adding an additional ground wire. The wire goes from C217 to the bottom leg of R104(one of those 3 big standup green resistors in the lower left of the board.

I have attached a couple of pix. The normal ground for that chip has to wind its way all the way around the board and at some points the traces get mighty thin. Left stock, there is about 22mV of ground noise on the ground for IC201. Adding the direct ground wire eliminates that noise. It can only help.


Pics, as mentioned:


http://imagizer.imageshack.us/v2/xq90/909/4NmZe4.jpg


http://imagizer.imageshack.us/v2/xq90/743/iAdzSk.jpg


Knowing Kevin, he’s probably onto something. So who fancies having a go at this mod and reporting back the results? :)

Marco.

[Wakefield Turntables]

Have we got measured proof that the extra earth wire will removed 22mv of noise?

Secondly, is 22mv of ground noise really apparent on listening sessions?

Thirdly, I'd like the opinion of people like Nick Gorham, Paul Hynes on the subject just for an independent opinion.

[Mr Kipling]

Does he still keep in touch with Roland?

[Marco]

Have we got measured proof that the extra earth wire will removed 22mv of noise?

Secondly, is 22mv of ground noise really apparent on listening sessions?

Thirdly, I'd like the opinion of people like Nick Gorham, Paul Hynes on the subject just for an independent opinion.

Sure, and perhaps that will be forthcoming. However, my view, if you’re handy with a soldering iron, is simply to try it, see if you can hear a difference, and then judge things for yourself. Kevin knows what he’s doing, and as knowledgeable as the people you’ve mentioned no doubt are, he’s been modifying the Technics longer than any of them! ;)

In terms of the claimed noise reduction, I suspect that he’s measured it, otherwise why would he come up with that figure?

Kevin’s the man who started the whole Technics modification ball rolling, so when he recommends something to me for the Techy, I usually sit up and take notice. I'll certainly be trying the mod myself next time I’m down at Duncan’s or Anthony’s.

Marco.

[Andrei]

I trust Kevin, and will give it a go. But when? I have leftover super dooper silver wire that was mined from Mt Ararat and can use that.

[Marco]

Cool. Let us know how you get on Andrei :)

Marco.

[struth]

I trust Kevin, and will give it a go. But when? I have leftover super dooper silver wire that was mined from Mt Ararat and can use that.


Was it stripped from the Ark?:eek:

[Andrei]

Was it stripped from the Ark?:eek:
Yeah that's right Grant. It was in the navigation system.

[ChrisKemp]

Very interesting and I'll will follow this thread! And I'm with you there, Marco. When David write something like this, I too sit up and listen:)

[Marco]

David, who he? ;)

Marco.

[Paul Hynes]

Hi Andy,

22mv of ground noise on the AN6680 could be significant if this is referred to the ground potential of any circuitry connected to the AN6680.

I would be inclined to investigate the effect because, as Marco points out, Kevin has been modifying the SL1200/1210 for a long time and has accrued much experience. The standard board does have its limitations regarding track routing of ground and power lines.

Unfortunately my SL1210 is stripped down ready for an electronic rebuild so I cannot apply, measure and try this mod at present.

Regards
Paul

[Andrei]

The description of "The wire goes from C217 to the bottom leg of R104 (one of those 3 big standup green resistors in the lower left of the board." suggests one wire. So far so good. But pic 2 shows two black wires connected to R104. What is the 2nd black wire for and where does it go? Any ideas?

[Clive197]

The soldering looks very messy to me. I'm not sure I could do any better but still.

Clive

[Macca]

Does he still keep in touch with Roland?

No, but I understand that he and Ann Diamond still exchange Christmas cards....

[Wakefield Turntables]

Hi Andy,

22mv of ground noise on the AN6680 could be significant if this is referred to the ground potential of any circuitry connected to the AN6680.

I would be inclined to investigate the effect because, as Marco points out, Kevin has been modifying the SL1200/1210 for a long time and has accrued much experience. The standard board does have its limitations regarding track routing of ground and power lines.

Unfortunately my SL1210 is stripped down ready for an electronic rebuild so I cannot apply, measure and try this mod at present.

Regards
Paul

paul,

thats great would it be of any benefit to those of us that have your regs installed?

andy

[Marco]

The description of "The wire goes from C217 to the bottom leg of R104 (one of those 3 big standup green resistors in the lower left of the board." suggests one wire. So far so good. But pic 2 shows two black wires connected to R104. What is the 2nd black wire for and where does it go? Any ideas?

I shall ask Kevin and report back :)

Marco.

[Paul Hynes]

Hi Andy,

I cannot answer that at present. I would have to do some testing on a running unit to assess the source of the noise and the effect it is having on the circuit and the regulator reference points. When I rebuild my deck I will not be using the old motor board. I will have to leave it to someone else to do the mod and assess the results.

Regards
Paul

[Marco]

Hi Paul,

Sounds like you're busy, mate! :)

Regarding Kevin's tip, I can't see it doing any harm trying it, can you? IMO, you'll either hear no benefit whatsoever, or there could be a free sonic upgrade to be had, simply by soldering a wire, from one point to another. Not exactly a big effort.

Therefore, trying it is a bit of a no-brainer, really...

Marco.

[Wakefield Turntables]

Hi Andy,

I cannot answer that at present. I would have to do some testing on a running unit to assess the source of the noise and the effect it is having on the circuit and the regulator reference points. When I rebuild my deck I will not be using the old motor board. I will have to leave it to someone else to do the mod and assess the results.

Regards
Paul

Ok no worries paul, thanks for the input anyway.:)

[Wakefield Turntables]

Hi Paul,

Sounds like you're busy, mate! :)

Regarding Kevin's tip, I can't see it doing any harm trying it, can you? IMO, you'll either hear no benefit whatsoever, or there could be a free sonic upgrade to be had, simply by soldering a wire, from one point to another. Not exactly a big effort.

Therefore, trying it is a bit of a no-brainer, really...

Marco.

Yeah unless you develop a short and then fcuk up the main pcb and all your lovely regs

[Marco]

Which is why the job should only be carried out by someone with the necessary electrical competence! ;)

I'd never be tempted to try and do that stuff myself, which is why I let others with the necessary skills carry out the work on my behalf. The only folk who get near the innards of my precious Techy are professionals!

Marco.

[Audio Al]

I trust Kevin, and will give it a go. But when? I have leftover super dooper silver wire that was mined from Mt Ararat and can use that.

If you dont have enough
super dooper silver wire that was mined from Mt Ararat

You could use some Slik :sofa:

[Paul Hynes]

Hi Marco,

Yep, very busy at present. I am still behind schedule with the custom build stuff. It is surprising how long it takes to catch up when you get behind schedule. I am also getting ready to transfer some more power supplies and the fet head amp and fet phono stage over to PHA Ltd this Autumn. Then I am going to delete the custom build operation. This will then free up much more time for product development.

Back on track, regarding Kevin’s tip. I can see no harm in trying it.

Andy,

Have you got a decent soldering iron yet? You could practice soldering and de-soldering on some old scrap circuit boards from dead equipment.

Regards
Paul

[Wakefield Turntables]

Hi Marco,

Yep, very busy at present. I am still behind schedule with the custom build stuff. It is surprising how long it takes to catch up when you get behind schedule. I am also getting ready to transfer some more power supplies and the fet head amp and fet phono stage over to PHA Ltd this Autumn. Then I am going to delete the custom build operation. This will then free up much more time for product development.

Back on track, regarding Kevin’s tip. I can see no harm in trying it.

Andy,

Have you got a decent soldering iron yet? You could practice soldering and de-soldering on some old scrap circuit boards from dead equipment.

Regards
Paul

Paul,

I can solder but look what happened last time, my deck had a nice holiday on your island for a few weeks! :lol: I'll wait and see exactly how this mod pans out before I have a crack.

Andy

[Nigel]

Couldn't it be successfully tried out by simply carefully attaching the wire around the legs of the components, without soldering?

[RobbieGong]

Interesting thread Marco, thanks for posting. I'm looking to hopefully do open heart surgery on my techie this Saturday with install of bearing base plate. I'd love to try this earthing mod at the same time, while she's on the operating table :D Is there anyway you could ask Kevin to send over some very simple step by step pics of what to do as the two pics supplied are not obvious to me in terms of what exactly needs to be done. Would be a great help if pos - please :)

[Nigel]

Any more news / thoughts on this tweak?

[Marco]

I’ve not had a chance to contact Kevin yet, as requested by Rob, but will be doing so later today. When he replies, I will post his response here :)

Marco.

[Nigel]

Many thanks. Yeah, it's that other wire from the resistor that's confusing.

[RobbieGong]

I’ve not had a chance to contact Kevin yet, as requested by Rob, but will be doing so later today. When he replies, I will post his response here :)

Marco.

Thanks Marco, Much appreciated - ATB.

[Marco]

Just emailed Kevin :)

Marco.

[RobbieGong]

Just emailed Kevin :)

Marco.

Cheers boss :)

[ChrisKemp]

David, who he? ;)

Marco.
Or Kevin:doh:

[Marco]

Ok, just in from Kevin:


This was the outcome of work I was doing related to the half speed function. It was running the deck at 16rpm that revealed the need for better grounding.

Turns out that those three resistors are all tied to the main ground. The other wire you see goes off to the half speed circuit board which you cannot see. This is the best place to put any additional grounds.

Hope that clears that up.

Kevin


So, basically, ignore the second black wire! :)

Marco.

[dimkasta]

I had a quick look at a spare board I have around.

First of all, there is an error in either the description or the photo.
The description talks about R104, and we see the wire connected to R102. R104 is on the other side of the chip. R102 actually makes more sense, since that side of it is connected to the ground, while R104 has a cap between it and ground. I see no reason though why to connect the wire to this particular resistor and not the central ground screw spot.

Second, if you cannot find C217 it is because it is not there in some MK2s. It was a late addition in the schematic, probably a revision before the release of the next brother. C217 and C218 are not even included in the vinyl engine service manual.

That said, I searched a bit where that leg of C217 goes, and it seems to link to leg 17 of AN6680 which connects in its turn to leg 5 of AN6675 and can be tested by point TP9, all according to the schematic at 5V and not ground.

We need more info before we try this :)

[Wakefield Turntables]

I had a quick look at a spare board I have around.

First of all, there is an error in either the description or the photo.
The description talks about R104, and we see the wire connected to R102. R104 is on the other side of the chip. R102 actually makes more sense, since that side of it is connected to the ground, while R104 has a cap between it and ground. I see no reason though why to connect the wire to this particular resistor and not the central ground screw spot.

Second, if you cannot find C217 it is because it is not there in some MK2s. It was a late addition in the schematic, probably a revision before the release of the next brother. C217 and C218 are not even included in the vinyl engine service manual.

That said, I searched a bit where that leg of C217 goes, and it seems to link to leg 17 of AN6680 which connects in its turn to leg 5 of AN6675 and can be tested by point TP9, all according to the schematic at 5V and not ground.

We need more info before we try this :)

Dimmy,

Well done you have probably saved a few 1210's and this is exactly why I wouldn't do this mod.

[RobbieGong]

I had a quick look at a spare board I have around.

First of all, there is an error in either the description or the photo.
The description talks about R104, and we see the wire connected to R102. R104 is on the other side of the chip. R102 actually makes more sense, since that side of it is connected to the ground, while R104 has a cap between it and ground. I see no reason though why to connect the wire to this particular resistor and not the central ground screw spot.

Second, if you cannot find C217 it is because it is not there in some MK2s. It was a late addition in the schematic, probably a revision before the release of the next brother. C217 and C218 are not even included in the vinyl engine service manual.

That said, I searched a bit where that leg of C217 goes, and it seems to link to leg 17 of AN6680 which connects in its turn to leg 5 of AN6675 and can be tested by point TP9, all according to the schematic at 5V and not ground.

We need more info before we try this :)

Cheers Dimmy, Confirmation and clear instruction / pics with regards to what goes where is required. Hopefully this will be forthcoming at some point and avoid any of our beloved Techies goin' up in flames :eek:

[Marco]

I'll quiz Kevin about this further and see of he can post a few more pics, which show more clearly exactly what is going on :)

Marco.

[RobbieGong]

I'll quiz Kevin about this further and see of he can post a few more pics, which show more clearly exactly what is going on :)

Marco.

Top bloke Marco :)

[Andrei]

I'll quiz Kevin about this further and see of he can post a few more pics, which show more clearly exactly what is going on :)

Marco.
Fanks

[Marco]

Latest from Kevin, folks:


Hi,

OK, let’s be clear on exactly what we are doing. We are connecting a new ground wire from pin 8 of IC201 to the main system ground.

If you are technically sharp, you can go about this any way you see fit. Probably fair to say on all boards made after 1990 C217 is present on top and that makes the work easier.

C217 has one lead on pin 8 of the IC201. That is the ground power pin. That is the pin we are helping out with the new ground connection. The other end of C217 is the 9.7V supply. The picture shows connection to the correct end of C217, the end opposite pin 8.

But to clarify, we should simply say that we are connecting from pin 8 on IC201 to the main system ground. For me that was easiest done from the top as shown in my picture.

I clearly erred if I said R104, Those three large resistors are R102, 109, 110, and are all connected to the main power ground. Yes, you can connect to the central ground screw as well, but those 3 resistors offer a convenient spot as well.

Either way, the connection should be soldered to ensure long term reliability and the lowest possible resistance.

That’s an interesting observation on the vinyl engine schematic, I suspect though, that C217 is actually present underneath the pc board. On those early units, a lot of bypass caps were added under the pc board. And that may explain why it is not on the schematic.

With any internal mods, you should not attempt this if you have any doubts. And if your board does not match our picture, you will need to be more careful how you approach it. It is best to have some technical knowledge, ability to read a schematic and to use basic test equipment. If you have doubts that you are connecting to power pins and not to ground pins, a voltmeter can be your friend.

Let me know if you need more info.

Kevin


:)

Marco.

[dimkasta]

Yep sorry... My bad...

I probably confused the sides of the chip while flipping the board to check the pcb trace and failed to see the clear pin numbers... (lack of sleep?).

Makes perfect sense now...

Just a note. Should we score the old ground trace to avoid introducing ground loops?

[Marco]

I’ll ask him that one, too…

So who’s gonna give this a go now? :)

Marco.

[dimkasta]

I m on it :) probably later today

[Marco]

Cool - keep us posted on the results :)

Marco.

[RobbieGong]

I m on it :) probably later today

Cheers Marco / Dimmy,

Dimmy if you do do it could you kindly post some simple pics showing what goes where as that would increase my confidence. :). I didnt get to do the bearing base plate install this weekend so will try to do both at the same time.

[Marco]

Should we score the old ground trace to avoid introducing ground loops?

…and the word on this is:


Hi, I did think about that, but I don’t think this creates a loop. It just acts as if we beefed up the existing copper trace.

Kevin


:)

Marco.

[Marco]

Any joy on this yet, folks? :)

Marco.

[dimkasta]

sorry I ve been slacking... I started to do it but with all the new PSUs attached it was too much work to pull out the pcb...

I ll try to do it later today

[RobbieGong]

A pity this one's gone quiet !

[Marco]

Indeed - Dimmy, wotcha been up to? :)

Marco.

[Andrei]

I have bought a 2nd 1200 and am waiting for that.

[dimkasta]

Sorry guys I ve been sidetracked :)

It is a lot of work to disassemble it with all the new PSUs, so I keep postponing it.

Within the week i am waiting for some new PCBs so I will work on it again

[RobbieGong]

Sorry guys I ve been sidetracked :)

It is a lot of work to disassemble it with all the new PSUs, so I keep postponing it.

Within the week i am waiting for some new PCBs so I will work on it again

I know what you mean Dimmy, you sound like me and my bearing base plate. I just cant seen to find that space and quiet time to get the thing done. Not to mention I'm hoping to do a certain earthing mod at the same time once clear instruction / pics are made available :eyebrows:

[RobbieGong]

Somebody, Anybody ?? Surely we've got a few members who understand how this mod should / could be implemented ? There was a time when members would have been all over this stuf :scratch:

[Andrei]

Alas, the mainboard of the 1200 Mk2 I have does not show C217. Here is the pic:

http://i1279.photobucket.com/albums/y530/Andrei_nz/Mk2mainboard_zps01f5a4b1.jpg (http://s1279.photobucket.com/user/Andrei_nz/media/Mk2mainboard_zps01f5a4b1.jpg.html)

I'm sure Dimmy is right in that C217 would be visible from underneath. There seems plenty of space underneath to run a wire to the earth-point but that is now going to have to wait a week as I am lending this baby out.

[dimkasta]

Andrei I don t think C217 is there at all in older MK2s

Anyway, I quickly did a test today using a length of wire and two mini grabber hook clips to attach it.

There seems to be some slight change, making sound a bit sharper, but I cannot be sure since I am using a freshly soldered phono still burning in (not to mention that I am not very accustomed to its sound)

But with a pair of clips it should be a walk in the park to test without any fuss or commitment