Fun With The 401 [Archive] - The Art of Sound Forum

Thermionic

05-10-2010, 16:52

http://i161.photobucket.com/albums/t229/VPR5/Garrard401.jpg

I just set up my Garrard 401 again after our house move of 2 years ago. It’s mounted in a cut down version of a Lorricraft plinth which was made by them to fit a Target stand. But as that stand is currently supporting a TV, I plonked the black beast on my trusty ‘compute-fi’ trolly.

The arm started out an SME 3009 Series 2 (un-improved) with the steel knife edge bearings. But sometime later during a burst of reckless exploration I shoe-horned an FD200 damper on to it, wired it with 100micron cotton covered silver, shrunk adhesive heat shrink on the outside of the tube, and filled it with glass-loaded polyester resin. This was an attempt to provide something with a bit more mass and a little less resonance for the new Dynavector 30c cartridge I had just bought (also rather recklessly I think). It seemed to work well enough to stick with it, and 25 years later even my new Audio Technica F7 seems to be happy enough. It’s either the best sounding SME series II in the world, or the most worthless!:rolleyes:

Trouble with the new cartridge is, that while I had a slight 401 type hum with the old Dynavector, the new AT obviously has more bass and was kind enough to instantly remind me that Garrard should have decoupled their idler wheel like Thorens did in the first place. With no response to my call for help I decided that I would have to sort the problem out myself, or wreck the turntable in the process, but then again it would be a good excuse to get one of those Technics beastsies you guys are always on about.

Going through ‘various diagnostic procedures’ (fear not I am an Horologist) It became fairly obvious that the motor had a very slight vibration and this was being transmitted to the stylus via the idler wheel and the platter, standard problem some would say. So I took the deck to bits (sorry no pics) and ran the motor on the bench. There were no obvious problems or things bent, apart from a slight wobble at the circumference of the eddy current brake disc. This measured out at a very approximate 3/10th’s of a mm. This and the stepped pulley were removed from the shaft and the motor bearings were checked for slop; none found. So a couple of drops of sewing machine oil were applied to the bearings, and the disc and pulley were carefully put back at the correct heights. I had wondered what would happen if a 401 was transported without the motor suspension being screwed up, could the brake disc be damaged?

Anyway, in fine watchmaking tradition(!) I attempted with some care to reduce the wobble on the disc by careful use of something thin and flat against disc and motor housing. I called it a day at getting to around 1/10th mm vertical movement. With more time and perhaps use of the lathe I might have done rather better, but that may be for another time. Indeed perhaps a precision turned disc made from one slab of aluminium might be an answer.

Another interesting find was that the underside of the disc had 3 balancing marks. Were these just for the disc itself or for the stator and disc combination? So by trial and error I rotated the disc in relation to the motor shaft to get to the lowest perceived vibration, not completely gone but perceptibly improved. Feeling that I had done (quite) enough for the time being I put the turntable back together and put a record on.

To my relief the low level hum had all but disappeared and was now acceptable.:)

Not a very scientific conclusion I am afraid, as there seemed nothing much wrong apart from the 3/10th’s of a mm wobble on the eddy current brake disc. Perhaps oiling the motor bearings helped, or adjusting the brake disc / motor shaft relationship improved the overall balance of the motor. Who knows? Perhaps I might try a Variac and lower the voltage next. It was at least something to do on a wet Sunday afternoon last week.

DSJR

05-10-2010, 17:07

The eddy-current disc always was a possible source of vibration, although that cartridge needs a Sumiko headshell you know.....

I hope you're not one of those "antiquarian horologists" that seem to surround my neck of the woods. Anthing made in the last hundred years (unless bespoke and very expensive) is regarded with derision :(

Thermionic

05-10-2010, 18:04

Barry

05-10-2010, 18:48

Looks good Gino.

Do you find the heatshrink sleeving to be beneficial? Does it dampen the arm any more than the 'Rawlplugs' fitted inside the arm?

What are the cartridges, both fitted and in front of the Dynavector cartridge?

The Stellavox, just to the left looks nice. :)

Regards

DSJR

05-10-2010, 19:23

Sorry if I am going over well trodden paths here, just having fun.

Thought about a Sumiko and can’t seem to find my ADC, but the SME looks good for the time being don’t you think?

Not really a Horologist just interested, but I suppose mechanical watchmaking did indeed reach it’s peak a while back arguably with the Hamilton 21 in the 1940’s. Not too interested in modern stuff (few exceptions of course) and have a few examples from the Quartz Revolution in the 1970’s, but since then one could argue that things have not progressed that much.:)

The SME headshell looks amazing, but pre-conceived ideas about resonance and too low a mass for MC types get in the way ;)

My interest in horology has been in striking and chiming clocks of the 20th Century. These things are almost worthless now, yet even the most scorned striking movements with 1.6mm plates and cheap pressed-out wheels have some clever thinking in them, as tiny pivots and thin wheels means low torque through the train, therefore smaller lighter springs, therefore low wear potential. if these things were properly serviced every ten years or so, they'd show little wear at all, if any, judging by the 1930's/1940's Enfield strikers I have.

Back to Garrards, you ought to see their clock division's movements (1930 until 1955 or so)- built like brick out-houses and the strong springs power their way through all sorts until the large diameter pivots wear on the chime train..

I'll find some pics of some of my collection if you're really interested............................... I'm :mental:

Below two pics from Google of Garrard movements

http://i132.photobucket.com/albums/q8/DSJR_photos/Garrardstrikingmovement.jpg

http://i132.photobucket.com/albums/q8/DSJR_photos/GarrardWestminstermovement.jpg

Rare Bird

05-10-2010, 22:33

What are the cartridges, both fitted and in front of the Dynavector cartridge?

Aye looks like one of the 'Karat's layed at the front..

Looks great Gino

Alex_UK

05-10-2010, 22:49

Well, I still haven't got my 401 serviced or re-plinthed, but my god, these things are just so damned musical. I have rumble, but it can only be heard between tracks, even at the low levels I listen at usually. In my situation, (3009 S2 Improved/Nagaoka MP-15) a Sumiko headshell improved the rumble by quite an amount, it is barely perceivable now (although that wasn't why I bought it, and I don't understand the science behind why it would reduce rumble, but it did). The Sumiko is not as pretty as the (currently mislaid :doh:) original, though, in my eyes - but who cares when Kate Bush sounds as fantastic as she does just now? :)

Thermionic

06-10-2010, 09:39

Thanks for confirming my impressions Alex, when you live with something a long time you tend to take it for granted and only notice the obvious things (like rumble etc). Interestingly when swapping the little linear-tracking Technics with the 401, while the noise level went up (now largely fixed) I literally found myself boogying to the music like I do at live concerts! Thanks also for the comments on the Sumiko as there was a very obvious change between the integrated 30c cartridge and the AT-F7 in the SME shell as regards rumble. I will check this out and report.

Yup an original Ruby Karat which I think was a also known as a 23R. That’s mounted in a Technics shell that was intended for the AT. After all these years (and not much playing of LPs - this site is changing that!) it still seems ok, though I might be wrong…

To be honest I have no idea Barry if the heatshrink had a noticeable effect, I thought I needed to try and reduce any resonances as best I could in conjunction with the polyester resin (plastic padding car filler actually…), and it was easy enough to apply. I had to modify the arm rest as well but I suppose it may have added a bit of mass. For thin walled arms with just wiring in them and a removable headshell it may well be worth a try as it would be easily done and removed.

Fair point about the shells DSJR and I am learning here. Excellent on your horological interests, and you won’t need me to tell you that some of those quite modest movements were very fine examples of practical precision (such as vertical helical balance springs wound in both direction that comes to mind) and good production engineering employed. I think that even Marvin Whitney in his book ‘Military Timepieces’ praises the qualities of those cheap mass produced though accurate movements. I am even known to; when chatting about precision timekeeping, to open the back of my parents half Napoleon and point at the helical balance spring and say ‘that’s a spring just like they use in marine chronometers’.

Sorry getting a bit off topic here, and am a bit rushed as I am about to be dragged of to a regular hospital appointment any moment.:(

DSJR

06-10-2010, 10:19

Ooooh, the heaven and hell of the "Floating Balance" - ooh matron :eyebrows: :lol: Got a good few of those... Got a thus equipped Smiths "Hamilton" to 15 - 20 seconds per week and it kept this for years until one of the bushings wore down.

Alex, the 301/401 "rumble" isn't so much a poor bearing grumbling rumbling sound, but more like a 100Hz "hum" from the motor, coupled with harmonics further up the frequency band (even a very quiet "whine" in the background on some examples).

The important thing with these decks is to make sure the motor springs aren't being fouled by any of the wiring and that the wiring isn't dictating what the motor does. The idler rubber may have hardened a bit too and this is where Loricraft would better advise before laying out £50 or so on a new or refurbished one.

anthonyTD

07-10-2010, 18:29

something you could try is a copper disk that will fit into the recess in the top of the platter where the mat usualy fits, this may help by canceling the eddy currents coming through the platter created by the motor assembly beneath.
this may also help improve the 401's high frequency ability.
hope this helps.
anthony,TD...

Thermionic

08-10-2010, 09:17

Thanks for the copper disc idea Antony, but I am not sure if it is induced eddy currents causing the hum through the platter. What is interesting, though I haven’t yet worked out what is going on, is that the hum completely disappears for a few seconds if the speed adjust knob is turned about 50 or so degrees either way. Then after a few seconds the hum comes back.

This suggests to me that it is as if the whole motor assembly is slightly in resonance, and by moving the magnet’s position on the disc this temporarily upsets this resonance. Problem is that the eddy current magnet and the disc / motor are in a closed loop, which on the face of it suggests that it shouldn’t show this behaviour.

What I do wonder is that as the linkage controlling the magnet is also spring decoupled, the perhaps the change of tensions in all the various springs as the lever is moved simply damps the whole assembly for a few moments. So possibly some overall damping of the motor springing or the motor itself (perhaps fixed to a fluid dashpot of some sort) might be worth investigating. Indeed perhaps your copper disc might provide some damping, though I feel it is rather to far from the magnet to be significant, though it would of course provide more mass.

DSJR

08-10-2010, 13:47

Is the hum when playing records, or there if the stylus is lifted off? if the former, it's "the" thing to rectify with these decks (my first one was awful) and could well be the eddy-current disc having vertical motion.

Once again, check the dressing of the motor wires so it "bounces" freely on its springs, make sure the motor bearings are properly lubricated and that the motor sections are firmly bolted together.

Thermionic

08-10-2010, 18:03

Playing records, the hum is a mechanical vibration from the motor (within it’s spring suspension) via the idler wheel to the platter to the stylus.

There was vertical motion of the disc of about 3/10ths mm, which I reduced to about 1/10th mm.

The motor with the disc and stepped pulley removed was just perceptibly vibrating when held in the hand. The bearings seemed free and had no perceptible play, but were then oiled.

By trial and error I rotated the disc about the motor shaft for best perceived balance (and lowest vibration) of combined motor stator and brake disc.

I had previously established that the dressing of the leads etc was not a significant source of noise in this instance.

It occurs to me that while the spring suspension of the motor may decouple it from the deck it does not damp vibrations inherent in the motor such as a slight imbalance of the stator, or more possibly magnetostrictive effects in the windings. This is were a clean lower voltage from a special power supply or indeed an new idler wheel may be an answer. But I wonder if damping the motor with something like an oil-filled dashpot or some form of shock absorber (such as found in some radio controlled model cars) might be a rather more cost effective solution for myself.

anthonyTD

08-10-2010, 20:13

hi gino,
you have me wondering now and if i didnt know better i would suspect the motors vibration was down to something affecting its synchronous operation, ie, severe mains polution etc.
but it could just be down to the idler wheel setting up a resonance through the motor and by slightly turning the switch you are reducing the pressure from wheel to platter rim and momentarily the noise disapears.
just a theory mind you.
anthony,TD...

DSJR

08-10-2010, 22:12

I don't believe the 401 motor was synchronous at all, in the manner of the Synchro-Lab motors in some of the lesser decks and I still intend to find the article criticising the 401's motor stability on varying mains voltages, next time I visit HiFi Dave.

Not knowing the proper physics of the eddy-current brake, I put the motor vibration down to bad balancing of the rotor. I know that in 1974, the 401 was known to be very variable in production and one of the staff had to select one quiet new one out of four...

anthonyTD

09-10-2010, 09:21

DSJR

10-10-2010, 15:53

I'll do me best sir :)

The 401 and, I think, the 301 had "shaded pole" motors, which are basically variations of a four-pole induction motor I believe. Why Garrard didn't develop a beefed up version of the clever "Synchro-Lab" motors I'll never know, but you wouldn't then have been able to easily adjust the speed without (then) costly electronics to vary the mains frequency.

I believe the Synchro-Lab motors used the 4 pole induction side to give pretty rapid startup and the extra magnets around the rotor then helped lock onto the mains frequency coming in. This gave these motors better speed stability under voltage changes (which would make an induction motor slow down I think). I'm looking out for one for future turntable projects...