Garrard AT6 Autoslim - no rotation of turntable. Huh?

[David G4EBT]

Those comments are tending to confirm my suspicions - it's easy to stop the platter with one finger, and even though the central drive 'cog' on the platter is quite small and mating gear on the main cam which the platter has to turn is quite large, (and thus, there is a mechanical advantage), the idler has to start the platter rotating, and to overcome the resistance as the main cam rotates and performs the various actions - lift the tone-arm, move it across to the record and lower it down.

The fact that the platter can be stopped with one finger suggests that although the motor continues to revolve, the idler simply fails to grip the inner rim of the platter.

Thanks once more for your interest and advice guys.

[G4XWDJim]

I've often thought that the next time I have a similar problem with a hardened idler I'd freeze it and quickly clamp it in the lathe and with a very sharp tool machine a few mil off it before it thaws. I don't know how practical it would be but I'd like to try.

I think the lathe would have to be set up before freezing so that no time is wasted between taking it out of the freezer and starting to cut.

Maybe a domestic freezer might not reach a low enough temperature.

Anybody tried it?

Jim

[David G4EBT]

Howard came this morning as arranged and we spent an hour or so together. The N.O.S idler that he had was too small - the one on the Autoslim that I have is 2" diameter, but the visit was very worthwhile in that apart from making Howard's acquaintance, I was able to compare my idler with his to see how the flexibility of the rubber compared. I was pleased to note that mine does actually seem to be in quite good condition - it's as flexible as the one that Howard has, and with no cracks. I have a small Lorch watchmakers' lathe with collets, so I've just mounted the idler in a collet on the lathe and have cleaned the edge with 220G paper, making sure that it has a nice flat new surface.

I've remounted the idler on the turntable and it does now start and run fine every time on the manual setting. However, on auto, while it starts to run fine, as the platter turns the main cam, it meets a resistance (a 'heel' in the cam track?), stalls for a second or so, overcomes the resistance, comes up to speed again then after a second or two, switches off. The tone arm doesn't correctly move into position either, though it does make some movements. Hence, such problems as now exist seem no longer to be that the idler won't spin up the platter, but to be connected to the leverage and cam arrangements, though everything seems to move freely as it should, but clearly something is amiss.

So, it's progress of sorts!

At least the 'Dynatron GR8' will now play records on the manual setting, and it sounds excellent - no hum, and oodles of volume, even notched right down. The choice of model number by Dynatron 'GR8' pre-dated the 'text-speak' era by at least three decades, so maybe it's pure coincidence, but the amplifier certainly lives up to the name 'GR8' - 'great'.
I've now got 'Orange Blossom Special' buzzing around in my head from repetitive playing. (It was a modest UK hit in 1963 for Swedish group 'The Spotniks'). How embarrassing to rifle through my dormant collection of 45s from days of yore to find this amongst them! Oh well, it could be worse I guess - 'Day Trip To Bangor', Steeleye Span, or whatever!

I'm away from home for a few days from tomorrow, so the turntable will be having a rest from my antics, and I too will have a few days respite, but I'll be taking the manuals for a little 'bedtime reading'. On my return, I'll again go over all of the moving parts and joints to ensure that they move freely, and that they're lubricated where they need to be, and not where they don't. (The pawl mechanism moves perfectly freely). I'll look for a less irritating 45 to play.

[Half a Mullard]

Hi David

It was a great pleasure to meet you today and I'm sorry the idler didn't fit. However sounds like you are making progress - a few days break could work wonders!

Thanks again

[paolo]

The symptoms sound exactly like the autoslim problems I had in my Bush SPR31C. Despite the original idler seeming to be pliable and in good condition, it wouldn't run at the correct speed with the tonearm lowered, the turntable could easily be rotated backwards while on and auto operation was non existent despite the deck having been stripped and regreased. I had the idler rebuilt and the problem went away. Good torque, steady speed and flawless auto operation.

[David G4EBT]

Thanks for reading the thread Paolo and for your comments.

Having cleaned up the idler, (which seems to be flexible and in good condition visually), it does seem to work and spin the turntable at the correct speed, but only when used manually. I do now have an N.O.S idler on its way to me, so I'll fit that to see if it solves the problem of the auto-changer not working as it should. If not, despite having followed all the instructions on lubrication etc, I'll methodically strip the mechanism down bit by bit, clean it throughly and reassemble it.

I've been away for several days so haven't had chance to pick up where I left off, but when the new idler arrives it will spur me into action - at least that's the plan!

[Audio1950]

I think one of the most important parts to pay attention to is the eccentric groove in the underside of the large cog. It is most important to the smooth running of the mechanism that it is spotlessly cleaned and greased.

[David G4EBT]

Thanks for reading the thread and for that most interesting advice!

As found, there was no trace of any grease ever having been applied to the groove and the groove was clean. All that's said in the Service Manual about the cam is to 'lightly oil the bearing' - I can't see any mention in the Manual of the need to apply grease to the groove so I left it as it was, but it's a simple job to apply light grease to it, so I'll certainly try that. When I rotate the large cog (known as 'main cam' in the manual) by hand it moves freely, but there is a point at which it operates the levers, at which it meets resistance, which is easily overcome by hand and seems to be caused by the springs on the lever working as they should, rather than due to a lack of lubrication, but grease in the groove of the cam can, I think, only be too the good. I'll report progress/lack of when I've had a chance to get back on the case!

[thebirdman]

I'm also having fun with one of these decks. I had problems with auto mechanism, cleaned out the groove (which had some horrible old grease in it) and regreased, which has solved that problem and seems to have improved the speed of the turntable as well. Unfortunately somewhere in its previous life a spacer from the tonearm assembly has been removed, as well as the switch mentioned in the other thread

[David G4EBT]

I've greased the cam groove, but to no avail. Works on 'manual' and the idler rotates the turntable at the correct speed(s), but won't work on automatic. I'm still waiting for an N.O.S idler (in the post) to try and if that doesn't do the trick (extra 'torque' maybe so that the turntable doesn't stall on automatic?), I think that all I can do is to progressively strip down the mechanism taking pics at each stage, then clean everything up, lubricate as called for and reassemble.

No obvious faults such as springs fallen off, or old hardened grease, but I have just found a small (about 20mm wide I guess) horseshoe shaped hard plastic component in the bottom of the cabinet which has a 'dovetailed' shaped groove around its outer perimeter. It doesn't look damaged (ie, not snapped), but whether or not it has any significance I've no idea. I'm mystified as to what it's role in life is, and I can't see anywhere where it would fit like the last piece in a jigsaw puzzle. I've attached a couple of not very good pics. Reasonable to assume that it does belong somewhere, but quite where . Any ideas anyone please?

[Audio1950]

It slides into the front end of the headshell. These decks were supplied as standard with the Garrard GC8 cartridge, which had a very thick turnover knob shaft, and if another cartridge was fitted, with a thinner shaft, it left a wide gap, which looked unattractive, so Garrard supplied two adaptors, the one you have, and one on which the front was completely filled in, so that cartridges with "flip-under" styli could also be used.

[paolo]

I know what that is! It is a plastic cover from the front of the AT6 headshell. It is designed to cover the hole left from a turnover cartridge knob such as a TC8 when a different sort of cartridge is mounted such as a Sonotone 8TA, for example.

Paul

Damn! Beaten to the punch by two minutes by Audio 1950

[David G4EBT]

To update this thread, I'm happy to report a successful conclusion. Visually, the idler wheel seemed in good condition - pliable, no cracks or indentations and I'd roughened the edge with 180g wet and dry paper, but it still wasn't able to overcome the resistance presented by the heart-shaped cam to make the auto-player mechanism work. I eventually found a 'new old stock' idler wheel on e-bay, which I recently fitted - more in hope than expectation, but it worked right away. Quite pleased about that as I'd gone to some trouble to clean and lubricate all the mechanisms as directed in the service manual, and to restore the amplifier section on this Dynatron Carnival, replacing several resistors that had gone high in value, several capacitors, and fitting a new volume control on which the original on/off switch was open circuit.

Surprised that there appears not to be a UK firm that refurbishes idler wheels, given the resurgence of interest in Dansettes and the like, which now command prices of £400 upwards 'fully restored' from professional restorers and £200+ 'in need of attention' on auction sites , so I've no idea what they do about idler wheels, but at those prices, there is plenty of headroom to fit re-manufactured ones.

Long gone are the days when this stuff went unsold for a fiver, languishing in damp grass in muddy fields at windswept car boot sales.

[Radio_Dave]

Hi David,

I'm still wondering if you have a problem. Are both parts of the trip pawl free to move?

I've just stripped down and re lubricated a Garrard 2025 and if I turn off the motor, when the record's run off groves are reached the autochanger will operate, lift the tonearm and return it to it's rest with just the inertia of the platter. There's very little force needed to operate it.

Regards
David

[David G4EBT]

Thanks for reading the thread Dave.

Yes, both parts of the pawl move freely and always did, though I did strip it down, and cleaned and lubricated (or not as directed) all of the mechanism of the turntable in accordance with the AT5/6 Service Engineers Manual. If the turntable is in good order and working well, there are two points in the heart-shaped track beneath the cam at which there is a slight resistance as the cam operated the auto-changer mechanism. However given the large diameter of the platter rim compared to the small diameter of the idler wheel, with the 'mechanical advantage' which results from that, if you operate the platter by hand you don't notice the resistance, and with an idler in good condition it has no trouble overcoming that resistance. These two points of resistance can be felt with the platter removed and the cam rotated by hand.

I've attached two pics, the second of which shows these resistance points highlighted. the heart-shaped track in the cam isn't quite so obvious from above. incidentally, those pics are of another AT6 turntable which is unrestored, and I noted that the pawl mechanism was stuck solid, so clearly that is an issue with these turntables which causes them to malfunction. Also, on all of the points which were greased, the grease was solid with age. I was kindly given that turntable by forum member Mark James and had resigned myself to using it as a guide to completely strip down and reassemble the one that I've been working on in case I lost the plot when it came to reassembly. However, now that I've the fitting the new (old stock) idler wheel, the player works faultlessly both with 45 & 33 RPM records. As with your turntable, when the tone arm returns and the player switches off, the platter continues to revolve for a short while on inertia.

In this 'voyage of discovery' I've learnt quite a bit about how the mechanism works and how the pawl operates.

I can't begin to imagine the R& D which went into these really quite complex mechanical devices, let alone the tooling costs, and labour intensive assembly.

I own an apology to Audio 1950 and to paolo in that I didn't spot their helpful posts way back in May, which solved the mystery of the horse-shoe shaped plastic jobby.

The attached (poor quality) pic is of another AT6 headshell and the unsightly hole without the plastic in place is evident.

Many thanks to all for their helpful input to this thread.

[tracypaper]

Hi.
Maybe the inside of the platter is now 'too clean' and the paint on it has become too slippery? what I do is using a very fine wet and dry, lightly sand the inside of the rim, but with and up and down motion, not side to side following the curvature of the platter, re clean, Always works for me.
Gaz.

[David G4EBT]

Thanks for your comments Gaz.

Roughening the inside of the platter was one of the first things I tried, along with removing the glaze from edge of the idler wheel, using 220g wet and dry. I did all the other things mentioned in the Garrard service manual, including ensuring that the pawl moved freely, as it did from the outset. I took a couple of turns off the tensioning spring that tensions the idler wheel. The turntable would rotate and play manually, but the auto-changer wouldn't operate.

As soon as I fitted a new/old stock idler wheel bought off e-bay, that cured the fault and it all works fine. Quite voyage of discovery, but thankfully it's now all sorted and I know rather more about turntables than I did at the outset! I've come to the conclusion that the two most likely problems with turntables is seized up pawls (which mine wasn't) and non-functioning idler wheels, which mine was.

In closing, I should add that the detailed compendium of turntable faults and remedies that Darren put together is first class.

[Nickthedentist]

Yes, three cheers for Darren (and others') hard work.

Yours is not an uncommon tale. See this one from Andy a few years ago: https://www.vintage-radio.net/forum/...ad.php?t=40899

Nick.