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Inside a Telefunken S600 Belt-Drive Turntable

by Richard Elen on 3 Nov, 2016

in Audio Production

Inside a Telefunken S600 turntable

I hadn’t intend­ed to end up with more than one turntable, but I now have no less than four, all of which work. The most recent one I’ve been work­ing on is a Tele­funken S600, which turns out to be an excep­tion­al­ly well-designed turntable with a num­ber of inge­nious bells and whis­tles.

As I detailed pre­vi­ous­ly, I want­ed to replace the stan­dard tone arm on a Lenco L75 turntable with an Orto­fon AS-212. These are found (amongst oth­er places) on Tele­funken S600 belt-dri­ve turnta­bles, so I sourced one from Ger­many to steal the arm — but fel­low mem­bers of inter­net groups I belonged to were hor­ri­fied that I would do this to an actu­al­ly rather nice turntable. So I relent­ed, and one of my cor­re­spon­dents found a New Old Stock AS-212 that I duly installed on the Lenco.

Mean­while, the S600 arrived from Ger­many, in rather a sor­ry state. Despite being very well packed, the plas­tic cov­er was cracked almost in two and the back of the arm had gone miss­ing along with the coun­ter­weight. The well-known inter­na­tion­al ship­ping com­pa­ny had both dam­aged it and mis-deliv­ered it: the incor­rect recip­i­ent had opened it and lost some of the bits. So when it got here I wouldn’t have been able to pinch the arm for the Lenco any­way.

But now I had learned that these decks were actu­al­ly quite good, I decid­ed to attempt to repair it. And if it was actu­al­ly a good deck, I might want to use it as my main deck — in which case it need­ed a mod­i­fi­ca­tion to run at 78rpm.

Fix­ing the arm

img_2147The big prob­lem was the arm itself. This con­sists of an S-shaped arm tube with a bear­ing hous­ing on the end made of some mys­te­ri­ous hard rub­bery mate­r­i­al. A small tube con­tain­ing two sets of four 1.2mm ball bear­ings goes trans­verse­ly through the hous­ing and is held in place by two point­ed set-screws that have to be set up exact­ly right so that the arm sits cen­tral­ly in its hold­er with free­dom to move up and down but with no play. The hous­ing has an exten­sion stub on the back, and on to this mounts a thread­ed tube on to which the coun­ter­weight screws. In this case, the stub had snapped off the back of the bear­ing hous­ing and with it had gone the thread­ed tube and coun­ter­weight.

There were sev­er­al pos­si­ble solu­tions. Replace­ment bear­ing hous­ings are avail­able on eBay from time to time, made either of Del­rin or brass. The thread­ed tube is avail­able too. I could replace the bear­ing hous­ing (get the hous­ing off the arm tube, push the bear­ing tube through and put it into the new one, add the thread­ed tube and reat­tach the arm). I could con­sid­er get­ting a thread­ed tube and fit­ting some­thing inside it that I could push into the back of the bear­ing hous­ing and glue it in place. I got the bits to do the lat­ter, name­ly the thread­ed tube and some met­al-filled resin. But the pro­ce­dure seemed a bit dodgy, frankly. Would it stay stuck? Would the resin go where it shouldn’t? Would it look decent? I looked for a new bear­ing hous­ing instead, but found only brass ones, which seemed like overkill to me — the black Del­rin ones didn’t seem to to be avail­able at the time. But then a con­tact of mine kind­ly came up with a solu­tion: a com­plete replace­ment arm with the arm tube, bear­ing hous­ing (with bear­ings) and thread­ed tube — plus an orig­i­nal coun­ter­weight. Excel­lent. All I had to do was to fit the arm — and send the old one back to him.

img_2164The replace­ment arm assem­bly duly arrived, and is shown here. The sup­pli­er very kind­ly taped up the bear­ing hous­ing so the balls couldn’t fall out (I had obtained some spares in case they did, but I didn’t need them). First I need­ed to de-sol­der the arm leads, which meant get­ting the turntable out of its plinth.

This sim­ply required undo­ing three screws. Tele­funken real­ly designed these turnta­bles thought­ful­ly. You lift up the turntable, turn it ver­ti­cal­ly and then you can slide it into grooves in the plinth where it stands safe­ly so you can work on it.

img_2143Here’s the innards of the turntable, and there are a lot of things to talk about here in due course. Click on the image to see it up close. I de-sol­dered the arm wires (they attach to a ter­mi­nal strip bot­tom right next to the mut­ing relay) and then put the deck back in the plinth. I had armed myself with a pair of tiny cir­clip pli­ers with 1mm prongs to fit the lock-nuts sur­round­ing the bear­ing set-screws (one set of both on either side — you can see them in the bro­ken orig­i­nal arm image above) and now attempt­ed to loosen them. Pleas­ing­ly they loos­ened sur­pris­ing­ly eas­i­ly and I was then able to unscrew the set-screws enough to care­ful­ly lift the arm out. Thank­ful­ly the lit­tle ball bear­ings stayed in there too. So I taped it up ready to send off. The new arm went in with sur­pris­ing­ly lit­tle trou­ble too. First I led the wires through the arm col­umn by putting them into a drink­ing straw and push­ing that down the hole in the cen­tre of the col­umn. Then, using a busi­ness card as a feel­er gauge to cen­tre the arm in the mount­ing, I held the arm in place and gen­tly tight­ened the screws. Then hold­ing the screw in posi­tion with a screw­driv­er I tight­ened the lock­nut, first on one side, then the oth­er. It took about three goes to cen­tre the arm suc­cess­ful­ly and lock the screws in place, but the result was an arm that exhib­it­ed neg­li­gi­ble resis­tance when mov­ing in its bear­ings. Exact­ly what was required. This pic shows the new arm in place minus the coun­ter­weight.

img_2188The turntable was now back more or less to its orig­i­nal spec­i­fi­ca­tion, give or take. I ran it up and found that it reached 33 or 45 very quick­ly con­sid­er­ing the weight of the beau­ti­ful­ly-bal­anced plat­ter, and the speeds were rock sol­id. The touch but­tons for speed and stop all worked as intend­ed and the speed con­trol trim­mer knobs worked well. I hadn’t even had to replace the elec­trolyt­ic capac­i­tors. (If I had need­ed to, the infor­ma­tion required – along with lots more about these turnta­bles – is here.)

Bells and whis­tles

This turntable has sev­er­al bells and whis­tles. The main ones are to do with the arm lift. This can be actu­at­ed man­u­al­ly with the lever — there is a Belden-style cable from the lifter lever to a flu­id-damped dash­pot under the arm rest. There is a lock­ing arrange­ment that only lets the lever lock in the down posi­tion if the turntable is under pow­er, and if you hit Stop it lifts up the arm (and when the arm is lift­ed, inci­den­tal­ly, the relay men­tioned ear­li­er mutes the audio).

It is also intend­ed to lift the arm at the end of a side. This is accom­plished in a rather inge­nious way. Look at the pho­to of the under­side above and you’ll see that there is a slot­ted cop­per arc just to the left of the motor con­trol board. This is attached to a very light­weight arm that is linked to the ton­earm, and swings across under the turntable as the arm tracks a disc. Just next to the cop­per arc (which we’ll come to in a moment) is a V-shaped cutout. This is the clever bit. When the arm reach­es the end of a side, that V pass­es between a big frost­ed bulb (just below the cen­tre of the image) and a light-depen­dent resis­tor, shad­ing it from the light. (Why the V I don’t know: it will mean that the illu­mi­na­tion drops slow­ly rather than at once. Why?) This is detect­ed and hits Stop on the turntable, which also pow­ers-down a sole­noid to release the arm-lifter to lift the arm. That is what is sup­posed to hap­pen, but unfor­tu­nate­ly it didn’t work. In fact it is a lit­tle sur­pris­ing that the turntable would run with­out hold­ing a but­ton down. The bulb had expired. img_2144It looks very much like a W5W auto bulb but it’s only sup­posed to take 100mA. Luck­i­ly there are W5W replace­ment LED bulbs that run that kind of cur­rent so I popped one in. On pow­er-up this duly illu­mi­nat­ed, and now the arm lift­ed and the turntable stopped some­what before the arm reached the end of its trav­el, cor­re­spond­ing to just before the locked groove on a disc.

While we are look­ing under the turntable, let’s look at what that cop­per arc does. As the arm swings, it stops the light from anoth­er, small­er bulb, direct­ly to the right of the main bear­ing, from falling on the end of a light-pipe — that lit­tle clear tube going up to the top of the deck and past the orange string (which is the inter­lock between the pow­er switch and the arm lifter). It ends in a lit­tle bezel on top of the deck. The light is thus vis­i­ble from above the deck except when it’s obscured by that cop­per arc — which means the light is vis­i­ble when the arm is beyond the plat­ter and when the light can shine through the three slots in the arc, which cor­re­spond to the edges of a 7in, 10in and 12in disc. So basi­cal­ly it tells you where to put the arm for the start of a disc.

I thought the dri­ve belt a lit­tle stretched and worn so obtained a replace­ment from thakker.eu (for the S500, a sim­pler ver­sion of this turntable, but with the same motor/subplatter arrange­ment).

A speed mod

With the deck returned to its orig­i­nal spec­i­fi­ca­tion, next came the mod­i­fi­ca­tion I want­ed to per­form — to get it to run at 78rpm as well as 33 and 45. I had asked about this in the Vinyl Engine online forum and a gen­tle­man had kind­ly looked at the cir­cuit dia­grams I had found and sug­gest­ed how to do it. It turns out that this design of turntable was actu­al­ly licensed from Philips, though Tele­funken made some exten­sive sub­se­quent mod­i­fi­ca­tions. It’s a DC ser­vo-con­trolled motor arrange­ment, and in some of the orig­i­nal Philips mod­els using the same motor and con­trol board design, the turntable can actu­al­ly do 78 rpm right out of the box — so there was no rea­son why this shouldn’t work.

The answer, my respon­dent sug­gest­ed, was to put a resis­tor across the main 45rpm speed con­trol resis­tor (R133) to reduce its val­ue, then use the 45rpm speed knob to fine-tune the speed to 78. I decid­ed to go a lit­tle beyond that and put a trim­pot in series with the fixed resis­tor so that I could set the speed to 78 with the 45rpm speed con­trol knob in the cen­tre posi­tion as it was for 45, and not have to adjust any­thing unless I want­ed to run at a spe­cial speed like 80rpm for exam­ple. It took some exper­i­men­ta­tion to get the val­ues right: even­tu­al­ly I used a 47kΩ fixed resis­tor in series with a 10kΩ trim­mer. I sol­dered these to a minia­ture DPDT tog­gle switch that I mount­ed in the low­er right-hand side of the plinth, with a hole to access the trim­mer, and a LED and series resis­tor, pow­ered from the lamp sup­ply, on the oth­er poles of the switch so a red light comes up when you select 78. And it works beau­ti­ful­ly — here’s a Con­roy music library 10in 78 spin­ning at the right speed!

img_2191

Final­ly, I replaced the audio out­put cable, adding a pair of Neu­trik phonos in place of the orig­i­nal 5-pin DIN, and ran a chas­sis ground wire along the audio cable with a spade con­nec­tor on the end. In fact this is of lim­it­ed use as the mains on the turntable goes via a dou­ble-pole switch straight into a dou­ble-wound trans­former: the chas­sis and all the audio grounds are con­nect­ed togeth­er and have no con­nec­tion to the mains side. Untan­gling this to pro­vide sep­a­rate audio and chas­sis ground turned out to be a real pain — to retain the mut­ing relay func­tion would have required seri­ous rewiring — so I left well alone, and in fact it works fine, and the chas­sis can be con­nect­ed to mains earth if desired.

The turntable has a cast stro­bo­scope at the edge with its own neon lamp, but of course it doesn’t include 78, so I print­ed out an image of an old Gar­rard strobe for now and that works fine — maybe I’ll pick up one of the Lenco met­al ones at some point.

In oper­a­tion

img_2197So, now to try the turntable out. I mount­ed the Shure M97xE in a skele­ton head­shell orig­i­nal­ly acquired for my TT-100 and set it up for 16mm over­hang (tricky as you can’t move the arm to the cen­tre spin­dle: I cut a piece of wire to length as a mea­sure) and lined it up with a car­tridge pro­trac­tor: it lined up per­fect­ly. Set­ting the track­ing weight and anti-skate accord­ing­ly, I played a tone disc with the arm at dif­fer­ent posi­tions and the wave­form and sound were clear and undis­tort­ed through­out. I then played some music, and found this under-recog­nised turntable, believed by many to out-per­form many oth­er belt-dri­ve turnta­bles of the peri­od such as those by Thorens, was a mar­vel­lous per­former, deliv­er­ing an excel­lent, open and sta­ble sound just as I would like it.

img_2202

The only prob­lem I have now is what to do with all these turnta­bles. I real­ly don’t want to get rid of either the Lenco or the Tele­funken and I think the for­mer will end up on the main sys­tem down­stairs while the Tele stays in my stu­dio for tran­scrip­tion (along­side the excel­lent Tech­nics SL-7 lin­ear track­er, which doesn’t do 78).

 

{ 6 comments… read them below or add one }

Ammar January 16, 2017 at 03:04

Hi, I have the Telefunken S500. I have something to ask about these two turntables regarding the speed. Mine is quite accurate but looking at the strobe it has this sort of 'pulse', and it doesn't stay static. Is this normal?

I used to have a Marlux MX-86 direct drive turntable and it doesn't exhibit this behavior.

Richard Elen January 16, 2017 at 10:47

I don't notice that kind of behaviour on mine. I am afraid I don't know what might cause it, but if the pulsing is random and not regular, it's possible (I suppose) that the speed trim pot could have a dirty wiper contact. Otherwise I'm afraid I don't know.

However, the Telefunken motor and control system was licensed from Philips and is fairly well known. I got a lot of useful advice from members of the Vinyl Engine forum and you might like to ask there. You could even pick up my old thread:

https://www.vinylengine.com/turntable_forum/viewtopic.php?f=18&t=89318

Hope this helps!
- R

Ammar January 17, 2017 at 02:36

Thanks so much for your prompt reply. Its quite a task finding someone who has experience with this turntable.

I was in that thread too, I am one of the regulars in Vinyl Engine, but unfortunately there were no solutions to my issue. The pulsing isn't random or irregular, it is fairly constant almost like a breathing motion as I've mentioned. It is however quite minor so if you weren't paying attention you might not notice it. The speed also changes very slightly after running it a while and the internals have warmed up.

I've already replaced all capacitors and the voltage regulator too.

Richard Elen January 18, 2017 at 11:56

Sadly I don't have an answer to this one. The only other resource I've found for this turntable is http://www.tube-classics.de/TC/MyEquipment/Listening/LivingRoom/Telefunken-S500-S600-Ortofon.htm - and I think you've done the things mentioned there.

Klaus September 3, 2017 at 20:12

Richard: Loved your article!
I bought the Telefunken S600HIG+ new in around 1976 and I just received my beloved S600 here in CA shipped from Germany where it was stored the last 27 years. As soon as it arrived i switched to 110V and it did run, except the lift arm mechanism was 'frozen' shut from the old grease harden up.
I did open it up removed in a long process the old harden grease, bought Gradius S2 V100 3 and replaced it. Works well not plugged in.
Plugged in it does go down, but it does not rest on the vinyl and plays it, the mechanism pops up up and does not do what it should play the record.
Any input what I might have done incorrectly and/or should watch out.

I too believe that this turntable outperformed or at least is equal with the DUAL 1219 and Thorens 158.

Thanks.

Richard Elen September 16, 2017 at 12:35

Thanks for the comment! I am not entirely sure that I grasp what the problem is that you're having, but I have a few observations. On my unit the grease in the lifter mechanism has no doubt become a bit stiff as it takes a while to lower, but following a quick look at it I decided to leave it alone rather than risk ruining it by having it apart.

There is a system of interlocks that determines whether the arm will stay/pop up or lower on to the disc. Pressing the power button pulls a string that allows the lifter mechanism to function: without the power button depressed the arm will not lower. The string is like that found on radio tuners and I can imagine it could wear eventually and stretch or fail.

Then there is a solenoid that actuates when the turntable is spinning. This mutes the audio when the arm is lifted but also releases the lifter mechanism to raise the arm if you press Stop on the turntable speed buttons OR the arm reaches the end of the disc. The disc end detection is optical and controlled by a moving arm that occludes the light from the big lamp in the centre of the underside of the turntable.

A challenge with the arm/turntable combination here is that you can't practically adjust the height of the arm. As a result it is possible that the arm cannot lower enough to allow the stylus to reach the disc because the arm meets the lifter bar and cannot lower any further to touch the disc. If this is the case you may need a shim between the cartridge and the headshell to lower the effective height of the stylus in the "down" position. I am using an Ortofon PNP 2M Blue cartridge on this turntable (which sounds wonderful incidentally) and when lowered the arm is VERY close to the lifter bar. If the clearance was any less it would not allow the stylus to properly rest in the groove. I suppose another solution here might be to install a thicker turntable mat, which would have the same effect.

I am afraid I don't have much in the way of further ideas, but I hope these observations are helpful.

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