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Old 12th Sep 2019, 7:28 pm   #1
Grubhead
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Default Model Railway Controller HM 4000

Has anyone any experience of dealing with a Hornby HM 4000 power controller?
I have a problem with one side of the controller. It controls two trains. The Yellow side has no response.
I have looked on-line for the circuit diagram with no luck. Tried a model railway forum, which wasn't helpful also.
The link below shows the front image of one. I can see from that somebody must have put a yellow sticker on mine to identify the left-hand controller.
It was purchased knowing it was faulty.

https://picclick.co.uk/Hornby-HM-400...842880044.html

Last edited by Grubhead; 12th Sep 2019 at 7:30 pm. Reason: link test
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Old 12th Sep 2019, 7:47 pm   #2
SiriusHardware
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Default Re: Model Railway Controller HM 4000

Unfortunately that link is broken for me. Maybe post some images of the insides?

Here are a couple of images from Hornby's own web site, the first a view of the base HM4000 controller, onto which two more 'outboard' controllers can be mounted. I take it that what you have is the dual controller base unit without any additional left or right controllers?

The second image is a block diagram. From this we can see that the unit is likely to contain two of almost everything, except for the single mains transformer which appears to have three 16VAC secondary windings. One winding feeds the left side internal controller and the left external controller, where fitted. The second winding feeds the right side internal controller and the right external controller, where fitted, and the third winding feeds the AUX-Out supply terminals.

My first question would be, are you getting 16VAC from the 16VAC output terminals on the D-socket on the LEFT side of the controller? (This same 16VAC feeds both the internal left side controller and the additional left side controller, when fitted).

Edit: The block diagram was drawn by a Hornby forum member, and is not from an official Hornby document, so although the block diagram suggests that there are three individual AC outputs from the transformer, that may not actually be the case.

Edit#2: Your alternative link is working for me.
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Last edited by SiriusHardware; 12th Sep 2019 at 7:56 pm.
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Old 12th Sep 2019, 8:10 pm   #3
Radio Wrangler
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Default Re: Model Railway Controller HM 4000

You could also search under Hammant and Morgan (the H and the M)

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Old 12th Sep 2019, 8:20 pm   #4
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Default Re: Model Railway Controller HM 4000

The Hornby website suggests this unit was withdrawn as it did not perform very well and that it used "feedback control" [not sure what that is] as opposed to DCC [Direct Command Control with an integrated signal in the power line] which has much more flexibility in use and is compatible with all the modern stock. It's a bit beyond me as my Hornby stuff just had the basic variable resistor. but I can see the attraction. I'm sure the 4000 must be more sophisticated than that if you get it going [and the train].!

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Last edited by AC/HL; 12th Sep 2019 at 8:34 pm. Reason: OT aside edited
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Old 12th Sep 2019, 9:31 pm   #5
SiriusHardware
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Default Re: Model Railway Controller HM 4000

Feedback control: Measures the back-emf being generated by the locomotive motor so that it can tell how hard the motor is working, the aim being to keep the motor running at a constant speed even if the loco is going up and down gradients, otherwise it would slow down going up a hill and gallop unrealistically down the other side.

DCC is something completely different, here an constant-amplitude alternating serial digital signal is fed to the track all the time whether the trains are moving or not. In DCC all locomotives receive a common feed from the controller but there is a digital decoder in each locomotive, controlling a local PWM speed controller regulating the speed of the individual locomotive. Confusingly, the loco's internal digital decoder / speed controller may also employ feedback measurement for the same purpose as described earlier.

While more complex, DCC means that you can drive any locomotive anywhere on any track, even where there are several other locomotives resting on the same rails.

I don't expect this to be a DCC controller but it may be a traditional pure analogue controller or it might be a PWM based speed controller.
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Old 12th Sep 2019, 10:12 pm   #6
dave walsh
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Default Re: Model Railway Controller HM 4000

Thanks Sirius a very full explanation and you've filled in a few gaps for me there. The comment about another use of the feedback [in the speed controller] takes me past the point where I was always a bit lost

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Old 13th Sep 2019, 12:51 am   #7
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Default Re: Model Railway Controller HM 4000

Attached is a section from the nearly identical HM2000 manual. I don't know if you can read it but the first section says

Quote:
The 23VA transformer has three independent secondary windings, two of which provide the two isolated, pulsed DC, controlled outputs for train operation
That means the block diagram in post #2 is essentially correct. It also sounds like the speed control method is via an electronic PWM controller rather than an old school analogue rheostat.

The 'D' connector on the left hand side is meant to supply 16VAC to any extra controller you might plug in there but it is also a handy place to check that the 16VAC which should be going to the internal left hand speed controller is actually there, since the 16VAC for the internal controller on that side comes from the same transformer secondary winding.

I doubt whether the D connector carries anything more than one side of the 16VAC and the other side of the 16VAC. If I'd chosen the wiring scheme I would have made all the pins on one row of the connector AC(1) and all the pins in the other row AC(2). Power it up and look for 16VAC first on the RIGHT hand 'D' connector since you know that channel works. Once you know which pins should have 16VAC on them, look for 16VAC on the same pins on the left hand 'D' connector.
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Old 13th Sep 2019, 6:59 pm   #8
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Default Re: Model Railway Controller HM 4000

Thanks guys. Looks like I have some work to do on it.
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Old 14th Sep 2019, 3:31 am   #9
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Default Re: Model Railway Controller HM 4000

The HM4000 is a PWM controller and uses an ST62T60C6 microcontroller.

No service info or schematics around that I know of, but you could try Hornby and ask for the information.

I would be tracing backwards from the outputs and comparing one side with the other.

You might be lucky and it is just the output driver that is faulty.

At worst the micro could be faulty which would be the end of it.
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