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Offline luckas  
#1 Posted : 15 April 2021 13:47:40(UTC)
luckas


Joined: 06/02/2002(UTC)
Posts: 174
Location: ,
Greetings friends,

I've recently upgraded my 7286 turntable with a 7687 decoder. In the process I've noticed that the small turntable motor is really struggling. I've disassembled, noting that even the very slightest finger pressure on the cog while the motor is operating produces motor 'straining'.

I wonder if it's a power issue. As per the instructions, I'm running it entirely from my CS3, which in turn powers my entire layout. I had previously run the turntable via a 6021 and separate transformer (yellow and brown power directly from a separate transformer to the 7286 controller).

If it is voltage related, is there an alternate way of connecting the 7687 to take advantage of an unused transformer? It's not obvious to me that the 7687 can be cabled in any way other than directly to the B & O of the general layout.

In every other way, the motor and it's solenoid appear to be working perfectly. It just appears suddenly 'underpowered', if that makes sense.

Many thanks,

Paul
Offline twmarklinfan  
#2 Posted : 15 April 2021 17:45:41(UTC)
twmarklinfan

United Kingdom   
Joined: 08/05/2015(UTC)
Posts: 235
Location: Tunbridge Wells, Kent, United Kingdom
Hi Paul,

You could be into something about the total power requirement of the layout. Can you disconnect all your other solenoids etc and only have the turntable conncted to your CS3? If you can and it works fine you have reached the limit and you will need to think about adding a booster to your layout. If the turntable is not happy then you know the issue is with the turntable or perhaps the decoder

Adrian
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Offline luckas  
#3 Posted : 16 April 2021 10:46:18(UTC)
luckas


Joined: 06/02/2002(UTC)
Posts: 174
Location: ,
Thanks Adrian, that sounds logical enough.

Interestingly, I was mucking around with 'programming' the turntable in my CS3 again, and noticed that motor speed suddenly improved. This left me wondering if my previous attempts at programming had somehow affected motor speed? It seems unlikely, but perhaps anything is possible given the voodoo associated in setting up the turntable for digital operation.

Paul
Offline mvd71  
#4 Posted : 17 April 2021 01:05:33(UTC)
mvd71

New Zealand   
Joined: 09/08/2008(UTC)
Posts: 1,352
Location: Auckland,
It’s possible the mechanism was a bit stiff and the more regular use while programming has helped free it up
Offline JohnjeanB  
#5 Posted : 17 April 2021 12:38:00(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 1,518
Location: Paris, France
Hi Paul
If the 7286 turntable (TT) mechanism is clean and (lightly) lubricated there are many things which may cause friction:
  • Installation issue: the cut in the base plate is not circular and the plate is not exactly plan and horizontal. The result of improper installation is friction between the bridge and the circular pitt

  • Some tracks leading to the TT are straining the TT. This may lead to tracks pushing or pulling to the TT or exerting an angular torque

  • There are many contacts between the TT and the frame: inside contacts that you seldom access but more you have the outside contacts at bridge track extremity. If not used, cut them or bend them downward so that they don't add friction

  • make sure that the spring pushing the entire motor and gears is not too strong

  • Lubricate gently the large gear axle where a lot of friction occurs

7286 Motor2.jpg
I have a 7286 since 7 years which is used very heavily and works like a charm
Here it is in operation with a sound module and DSD2010 decoder


To be honest in all these years I never had to clean or lubricate the mechanism but using the DSD2010 decoder, the feeler "sword" and the unlaching relay is removed and replaced with a photo-coupler and signal disk for position (where to stop). See below on the left the optical disk for positioning. Here it is shown without the signals and soud modules (added later)
7286 Buhne mit Decoder.png (3,152kb) downloaded 17 time(s).

I hope this helps
Jean
My layout videos
latest vid
hump yard
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Offline luckas  
#6 Posted : 19 April 2021 02:34:05(UTC)
luckas


Joined: 06/02/2002(UTC)
Posts: 174
Location: ,
Thank you Jean, that's an impressive video. My rotation has returned to normal, and I'm not sure why, though I suspect it has something to do with my early attempts to program the decoder, as well as a general disassembly and clean.

I'm now at the stage where I'm trying to program events with the turntable. I am having some success, but I've found that the ability to select track position isn't working reliably. Single step movements left and right work perfectly, which provides some ability to program events but relies in the bridge starting at a known position.

I wonder if this is a known issue? I haven't been able to find very much information on event programming with the 7286 / 7687 combination.

Paul
Offline JohnjeanB  
#7 Posted : 19 April 2021 08:13:55(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 1,518
Location: Paris, France
Hi Paul
I don't have the 7687 decoder (rather the DSD2020) but I heard some forum members complain about the turntable (TT) position at start-up on some 7687 (or 7685?) not being properly memorized.
To be honest, I had the same problem initially when setting up my TT with Rocrail and on occasions when starting the layout, I may have to correct my TT position manually. After that all is OK.
I will look further to see what they say on Stummi Forum (Largest train forum in Germany)
Cheers
Jean



My layout videos
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