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Heljan 7mm Class 20


brian daniels
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So, I finally got around to breaking into my 20 to install the decoder etc.  I literally broke the steps getting the body off.  These are flimsy plastic affairs so I will look into replacing them with brass from my scrapbox.

 

However, I'm feeling daunted by the plethora of connections on my replacement circuit board.  I can match up the motor and rail connections but there are a bunch more, for the lights I assume.

 

Can anyone give me guidance.

 

Here's mine:

 

P1010021-001.JPG.1ada3d253544a90d69435ea1b2048294.JPG

 

It is the Zimo from Digitrains:

 

P1010024.JPG.5ffeac355b53ac6623a9dba96648d465.JPG

 

Thanks

 

John

 

To clarify, the Stay Alive connections are clear but the speaker connections are not.  The F0x connections on the board are probably for lights.

Edited by brossard
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Hello John,

 

I'm not familiar with using an adapter board, but what actual sound decoder have you plugged into the adapter board?

I'm wondering if the adapter board has a multiple use for both sound and non-sound decoders?

If so, it might be that you would have to use the speaker outputs on the actual sound decoder, just a suggestion though John.

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Hi Robin, the decoder came to me plugged into the board.  It is MX644C.

 

I'll hang on a bit to see if anyone else can enlighten.

 

It seems to me that Heljan are unique (certainly in my experience) in needing a replacement board.  All my other locos (Dapol) have just needed the decoder plugging into existing board.  I have two that I had to hard wire.

 

John

Edited by brossard
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I have made some progress.  I found this on the Digitrains site:

 

https://www.digitrains.co.uk/shop-by-product/sound/uk-sound/diesel/class-20/class-20-activedrive-sl.html

 

There is some useful information and a function list.

 

I made a sketch of the analogue board connections and wire colour.

 

I then disconnected the wires and unscrewed the board from the chassis.  The replacement board is not a fit so I made a plasticard adapter and fitted all that.

 

I have done the track and motor connections, splicing extra wire on because there never seems to be enough.

 

The only lights on my model seem to be red.

 

Still hoping that someone can show what they did.  I am not in my comfort zone with this.

 

John

Edited by brossard
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Hi John,

 

Have a look at pictures on the YouChoos website for this decoder

https://www.youchoos.co.uk/Index-Detail.php?L1=Detail&Item=MX644

 

Under the photo of speaker wires attached directly to the decoder it says, " For models that do not have speaker connections, purple wires can be soldered directly to decoder socket pins (WARNING - invalidates Zimo warranty)"

 

Probably not what you wanted to hear, but I had to do some thing like this with with the Heljan Class 128 DPU.

 

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John,

 

Sorry, just come across your post.

 

Don't solder anything to the decoder, it will not be required. All the connections you require should be available on the screw terminals, that's the purpose of the adapter.

 

I can't shed any light on the Heljan wiring loom, you'll have to find out where each wire is connected.

 

Looking at your photos above, it looks like the current limiting resistors for the LEDs may be on the Heljan PCB. I don't see any at the LED end of the wires.

 

If you remove the PCB in such a model, you must put series resitors in all the LED circuits, say 1-2K Ohms, to protect them. Without these, they will blow instantly and will need to be replaced.

 

If you know you haven't added resitors there are none fitted already, I would suggest testing each LED before going much further.

 

If the LEDS are OK and protected, there is another matter to consider.

 

The potential issues you may be having are that on the MX644C, Function Outputs 3 and 4 are Logic Level only.

 

You are most likely wiring for Open Collector (aka Normal, Full Power), 'cause that's what most of us would expect, but 21MTC has two versions of the same standards.

 

You will need to amplify these outputs with a couple of transistors. (circuits for these are easy to find).

 

Alternatively, it would be easier to use lower FOs (if any are unused) or higher FOs which are Open Collector, then remap the function keys accordingly.

 

I can guide you through the mapping, but you need to get the wiring correctly connected first.

 

When you have wired the positive leads of individual sets of lights at each end to a positive terminal on the adapter and negative leads to the terminals of your chosen Function Outputs (probably marked FA 6, FA 7 and so on) , let me know what is connected to what and I'll give you the CVs to change.

 

Also, make sure you have the respective motor wires correctly connected. It's not unusual to find the wheels in each bogie turning in the opposite direction to each other!

 

Best regards,

 

Paul

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Happy to hear from you Paul.  Flippin' 'eck what a palaver.  Heljan really do need to up their game in this mostly DCC world of ours.  Dapol have done that and their locos are a doddle to fit sound in comparison.

 

I never thought about the diodes so that's a good point.  I might have some resistors lurking somewhere.

 

There are only red lights on the model so these need to be switchable on/off.  They will be mostly off I think since these are only needed light engine.  If all else fails the lights can be left off.

 

I spliced the motor leads of the same colour to each other so that should be OK. 

 

Oh dear, when you use words like "transistor", my eyes glaze over.

 

The other thing that occurs to me is power to the fan motor.  The connector is on the Heljan board so wondering how that would go.  I'm thinking that raw power from track isn't right.

 

Thanks for responding.  I will update on any progress.

 

John

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3 minutes ago, brossard said:

Happy to hear from you Paul.  Flippin' 'eck what a palaver.  Heljan really do need to up their game in this mostly DCC world of ours.  Dapol have done that and their locos are a doddle to fit sound in comparison.

 

I never thought about the diodes so that's a good point.  I might have some resistors lurking somewhere.

 

There are only red lights on the model so these need to be switchable on/off.  They will be mostly off I think since these are only needed light engine.  If all else fails the lights can be left off.

 

I spliced the motor leads of the same colour to each other so that should be OK. 

 

Oh dear, when you use words like "transistor", my eyes glaze over.

 

The other thing that occurs to me is power to the fan motor.  The connector is on the Heljan board so wondering how that would go.  I'm thinking that raw power from track isn't right.

 

Thanks for responding.  I will update on any progress.

 

John

Heljan with suggestions from us an others 'ARE' changing this, Ben is their UK guy and with thanks to him alone, things will be getting dead easy.

 

The Class 17 is due soon I believe.

 

Charlie dckits-Legomanbiffo

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7 hours ago, brossard said:

Happy to hear from you Paul.  Flippin' 'eck what a palaver.  Heljan really do need to up their game in this mostly DCC world of ours.  Dapol have done that and their locos are a doddle to fit sound in comparison.

 

I never thought about the diodes so that's a good point.  I might have some resistors lurking somewhere.

 

There are only red lights on the model so these need to be switchable on/off.  They will be mostly off I think since these are only needed light engine.  If all else fails the lights can be left off.

 

I spliced the motor leads of the same colour to each other so that should be OK. 

 

Oh dear, when you use words like "transistor", my eyes glaze over.

 

The other thing that occurs to me is power to the fan motor.  The connector is on the Heljan board so wondering how that would go.  I'm thinking that raw power from track isn't right.

 

Thanks for responding.  I will update on any progress.

 

John

 

John,

 

You may be lucky in not having had any sizeable power to the LEDs yet due to unfinished circuits!

 

The red light, which you now infer is 'always on' is a clear indication that it's connected to a Logic Level only FO.

 

I agree things can be a little complicated, but don't panic, we'll sort it.

 

You wired the motors colour for colour. Well, whether that's OK or not depends on the age of your model. In early versions, the bogies are wired identically, but of course they are deployed in mirror image. That's what can give rise to the wheels rotating in opposite directions.

 

I've not handled a more recent model, but they may have made the colour coding a bit more intuitive.

 

In any case, test, test, test! Don't make any assumptions.

 

So, disconnect the red LEDs from the FO you have used and find other unused FOs to connect to. When you have connected the negatives for your LEDs etc to FOs (FAs) and positives to the common positive on the decoder, report back.

 

The fan can be connected to the adapter in the same way, just find a spare FO, avoiding 3 and 4 as described in my earlier post. Us ethe fan's PCB if there is one, to regulate the speed using the small variable pot on the board. (Small screwdriver slot).

 

Good work by Charlie and many others to finally get Heljan to 'get with the programme' re plug and play. It should make things much easier in the future.

 

This will not make any difference, though, if you intend to use the smaller decoder types, since the new Heljan O gauge plug and play solution is designed for large scale decoders. Worry about that when it happens. LOL.

 

Best regards,

 

Paul

 

 

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Hi again Paul.  The first thing I did was disconnect everything.  I haven't tested yet so no power has been applied.  Your notes for the ZS20ASL provide advice on where to connect the lights so I was going to follow that.  There's a link above.

 

I have seen other descriptions of adding sound to this model and a couple of them talk about removing one motor.  I gather that is because of current limits for smaller decoders.  I'm not sure where the MX644C fits.  I plan to leave things alone unless advised different.

 

Cheers for now

 

John

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I was a bit worried when I started this conversation that I was being thick.  However, after what Paul has said, I think my concerns about adding sound are well founded.

 

Today's work session:

 

- I took Paul's advice and tested the track/motor connections.  Sure enough, the motors were turning in opposite directions when I applied power.  I rewired, splicing orange from one motor to the grey of the other.  Now the loco runs properly.

- My next task was to fit the speaker.  True to form the speaker is just a smidge too wide to fit in the slot under the chassis.  I removed material (easier said than done with mazak) until the speaker just went in and I could get the fuel tank over it.

- I glued the stay alive to the chassis next to the board.

 

John

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17 hours ago, charliepetty said:

Heljan with suggestions from us an others 'ARE' changing this, Ben is their UK guy and with thanks to him alone, things will be getting dead easy.

 

The Class 17 is due soon I believe.

 

Charlie dckits-Legomanbiffo

Aww shame I got very used to the rats nest of wires from the decoder to the lighting in the 7mm Heljans, it only took me about three weeks to work out a wiring diagram and veroboard layout as well as finding out the origin of the Heljan sockets and order a batch from RS.........doesn’t seem like 10 years or so ago :lol:

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I'm feeling a bit better today.  I've wired in the stay alive and speaker.  I did a test run and sound works!  :smoke:

 

Here's where I am with it:

 

P1010022.JPG.45cc75864c8675e88e0f82f400dd2d96.JPG

 

I won't win any prizes for my wiring.  I spliced the motor and track wires but it would have been neater if I had used the duplicate connector bank on the right.  I only twigged to this after I had done the wiring.  Stay Alive is on the right next to the board.  I've no idea how to test this but I don't think it is essential.

 

Next up the lights.  You can see the loose wires for these.

 

John

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I just spent some time with the light wiring.  I spliced the blue wires (COM) together and put them in the COM + input.  I spliced the #1 and #2 wires together and inserted them in FO1 and FO2.

 

I also inserted 1K resistors into the wires for the lights in the body.

 

Still need to find a spot for the fan motor.

 

John

Edited by brossard
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On 05/02/2021 at 16:36, brossard said:

Stay Alive is on the right next to the board.  I've no idea how to test this but I don't think it is essential.

 

Just read in the 7mm modelling thread Improving Heljan Mogul slow running, Simon D mentioned pressing a piece of paper down to test stay alive and run it over that. If it gets most of the way across it's working!

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1 hour ago, Hal Nail said:

Just read in the 7mm modelling thread Improving Heljan Mogul slow running, Simon D mentioned pressing a piece of paper down to test stay alive and run it over that. If it gets most of the way across it's working!

I normally just stick a bit of masking tape over one rail.

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A couple of issues you raised not yet addressed, and another that I recall from some time ago.

 

1. Disconnecting one motor. The motors on these models are huge and power hungry. If you intend to operate at low/medium speeds with low weight on the hook, the MX644C or D will provide 1.8A continuous max which will probably be sufficient.

 

If you wish to be sure, or run at higher speeds with greater loads, you might find it beneficial to remove one motor and the gears from one of the bogies. (Compared to sorting the wiring, this is pretty straightforward, Lol).

 

If you intend running flat out in the garden with a heavy train in tow, then keep both bogies powered (for the improved traction) and replace the decoder and adapter with a large scale decoder like the MX696KS which will give you 6A continuous, more than enough.

 

2. Stay Alive testing. Power up the track, give a few seconds for the stay alive to charge up, then switch on the lights. Either turn off the power or lift the loco/rock to one side. With the stay alive pack you have fitted, the LEDs should be illuminated for a minute or more.

 

Do the same test with sound also on and you might be looking at 20-30 seconds.

 

Lift the loco with the motors running, and you should expect a few seconds until the motors stop, then the sound fizzels out the finally the LEDs extinguish.

 

It's pretty obvious if the Stay Alive is working.

 

3. I remembered that the early versions of this adapter, the caption on the board was incorrectly printed. It's probably been corrected on yours but if you have a terminal marked 'Cap +' on the long side then this is incorrect. It is, in fact, the 'Cap -'. so this is the terminal to which the ground or negative lead from the stay alive (black wire) should be connected. (Blue wire goes to Common Positive).

 

Best regards,

 

Paul

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Hi again Paul. 

 

On the motor, my layout is not large so trains will likely be 5 or 6 wagons or 2 coaches.  Speed will be low also.  Therefore, I will leave things alone unless I have issues.

 

Thanks for the tip on stay alive.

 

I will review what my board says, hoping it is correct since my board is new.

 

Cheers

 

John

 

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On 07/02/2021 at 02:11, boxbrownie said:

I normally just stick a bit of masking tape over one rail.


i just lift it off the track. No trees killed or glue from tape left on the rail in my method lol

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  • 4 weeks later...

Although the vast majority of my stock is OO I’m also building up a small fleet of O gauge locos and wagons. 6 months ago, I bought one of the last few pre TOPS Blue Class 20s. I would have preferred a TOPS model but couldn’t find one. Running it in shortly after buying it, the loco cut out on a couple of occasions but otherwise seemed ok. In total it ran for circa 45 mins. Reading various threads on here I did wonder if the cutting out may have been due to a split gear causing a motor to stall and draw too much current for my basic DC controller (I am DCC but have a Combi for running in) even although the 20s don’t feature in the list of suspect locos. I did a cursory investigation by removing the keeper plate from each bogie at the time. All seemed fine.

 

I had some time this weekend so decided to remove each bogie and do a proper investigation. After a considerable effort(!) I managed to remove the body (fortunately only damaging a cab step in the process) and unwired each bogie. On one bogie upon turning the flywheel very occasionally I felt some resistance and then heard a click, before the flywheel moved freely again. Closer investigation indicated that one of the gears, the one next to the wheel furthest from the motor, seemed to be binding. Not every time and not in the same place. However, the gear seemed fine. No obvious split and the teeth look fine.

 

I decided to try some further running in. A further 30 mins each way and the resistance has gone. Or more correctly I’ve not been able to reproduce the occasional resistance.

 

I’m going to run the particular bogie some more over the next several days just to be sure. Should I be concerned and is the above a possible indication of further problems or did the loco just need an extended period of running in? I have the option of returning the loco under warranty but with spares not available I wonder if it’s worth it.

 

In the event that I keep the loco I aim to change the headcodes for Dominos and move the double arrows to the bodyside. Has anybody had any success removing the supplied headcodes?

 

Thanks in advance

 

PJ10

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