Svein,

The best way to think of it is that the loco "forgets" the speed it was going at when it hits a momentary break in track current. It goes straight to speed step zero.

When, a moment or two later, it sees the track current again, it reads what speed it has been requested and proceeds to accelerate slowly up to it.

This is my interpretation of the "alzheimer effect".

Ray

Ray gave a rather accurate description. However, normally the lok remembers the requested speed, it only forgets that it was already driving at that speed. So usually it does not need to get a new command from the control station to accelerate up again, it just needs to get power back. Ray was a bit unclear by saying "it reads what speed it has been requested". It should in most cases mean "it reads what speed it has been requested, from its internal memory".

Per, thanks for the clarification. The effect you see is the same in either case.

The main point is that it makes a sudden attempt to stop, before accelerating slowly up to the original speed again. This is not very desirable, as it makes the interruption more pronounced and noticable.

Ray

Thanks, Ray.

I have other locomotives with the 60760 decoder that runs perfectly.

The advantage (if running OK) with this kind of decoder is that the maximum speed adjustment has a very big range.
I don't care so much about model accuracy, but the max speed as close to prototypical as possible is important to me. That is why I try to use the remotely adjustable decoders in the slow running locomotives.

I will test another 60760 decoder in the orange locomotive.

In the ESU decoders and in at least some Hobby loks, (and I think also in the 60760 but I'm not sure) there is CV 73 which selects whether the lok should remember its current actual speed or not. CV 73 set to 7 gives the "Alzheimer" problem, CV 73 set to 3 causes the lok to start abruptly after a power on, which can also be a problem. You can select which problem you dislike the least. Newer Märklin loks have either the CV 73 set to 3 from the factory or have the problem solved completely.

The "Alzheimer" is a secondary effect of a power drop. It is probably caused by a reset to the processor, followed by a non-optimal start-up behaviour. The Alzheimer may in some cases be cured by a capacitor that prevents the processor to go into reset.

There is of course also the primary effect of the power drop, where the motor stops because it gets no current. DC motors tend to stop more abruptly than the AC motors. That is one reason why you won't see this problem on the Delta and 6080 loks. The reason why DC motors are worse in this respect is that the magnet field is not shut off with the power as it is in the AC motors. There are two ways to compensate for this. Either you add a flywheel, or you add a capacitor. Unfortunately the capacitor needs to be rather big to make any real difference.

This problem is even worse with loksounds. I have a loksound in my ICE and when it gets the interruption, before it starts accelerating it has to go through all the start-up sounds again, which takes a second or two (seems like an eternity). Then it accelerates to speed.

Well, I have one (lokprogrammer). I must look into that

Thanks, Luis

I'm confused about this Alzheimer problem - more directly, how does one "cure" the problem? I have 2 locos with the problem and I want to know how to exactly cure them. Can someone please explain the procedure?

Like the real life Alzheimer's, there is no real cure.

A summary of the suggested fixes in this thread are:

- Replace the decoder with a newer one that is less susceptible (Lokpilot 3, 6091x)
- Set CV73 to 3 and see if that helps
- Apply firmware updates to older decoders - Lokpilot 2. Requires an ESU Lokprogrammer
- Investigate whether a capacitor can be fitted to the decoder to prevent momentary power loss.
- Make sure the loco's mechanicals and electrical connections are clean. Make sure the loco has good grounding
- Keep your track clean and fix any dead spots.

I'd like to add my results to this topic. A friend suggested to me that I setup a small section of track with a MS. I had 2 locos with the problem. I managed to correct one loco and not the other, so I guess there is some chance of rectifing the problem without changing the decoder, etc. I hope this helps someone else.

What did you do?


I placed the loco on the small loop I setup and manually typed in the loco's number - this is all done with the "stop" set on the MS. Then I pressed the "OK" and the loco took off as it has done in the past with Alzheimer's, however, after a few seconds the MS then can control the loco like normal. As I said it worked for one loco and not the other, so it's not a guaranteed cure. I hope this helps.