Hornby HST lights upgrade - Black Cat Tech

[Graham108]

I have a pair of HST's which are somewhere between 45 - 50 years old - still going strong. However the lights only worked in a forward direction and were very weak.

 

I saw an advert for an upgrade with a PCB supplied by the above. Fitted fairly simply by removing the bulbs and replacing with the PCB - I decided to remove the pins from the wires and solder direct to the relevant places on the board and also removed the diode which worked the lights according to direction of travel.

 

The non-powered units work fine, but in the powered cars both sets of lights are appearing at the same time, regardless of direction.

 

I know the PCB's work as I've powered them direct - but when powered by the wheels the fault appears.

 

Anybody used these and either not had the problem or managed to correct to make them work properly please?

 

Graham

[cliff park]

removed the diode which worked the lights according to direction of travel.

but in the powered cars both sets of lights are appearing at the same time, regardless of direction

um................

[andyman7]

43 minutes ago, cliff park said:

removed the diode which worked the lights according to direction of travel.

but in the powered cars both sets of lights are appearing at the same time, regardless of direction

um................

The diode needs removing because LEDs are literally Light Emitting Diodes and don't need an additional diode in the circuit - they will only work with the polarity in one direction.

 

Although I've used these units myself I'm at a loss without seeing the wiring in the power car to explain why both red and white LEDs seem to be illuminating in both directions - there must be some current contamination upsetting the pure DC path to the lighting board

[Kris]

I've used these without any issue. 

[Graham108]

10 hours ago, andyman7 said:

The diode needs removing because LEDs are literally Light Emitting Diodes and don't need an additional diode in the circuit - they will only work with the polarity in one direction.

 

Although I've used these units myself I'm at a loss without seeing the wiring in the power car to explain why both red and white LEDs seem to be illuminating in both directions - there must be some current contamination upsetting the pure DC path to the lighting board

I'll try and get some photos if you don't mind taking a look for me

Edited November 23, 2020 by bartram108
Additional info

[Graham108]

11 hours ago, cliff park said:

removed the diode which worked the lights according to direction of travel.

but in the powered cars both sets of lights are appearing at the same time, regardless of direction

um................

The original diodes are there so they white lights don't illuminate when the unit is trailling - i.e. at the back of the train

[andyman7]

5 hours ago, bartram108 said:

The original diodes are there so they white lights don't illuminate when the unit is trailling - i.e. at the back of the train

If it's the same lighting board I'm thinking of, it provides directional red/white lights so both ends are always lit red and the front/white at the back

 

[Pete the Elaner]

I've not had this problem but I am trying to think of what may be going on.

A motor is also a generator, with the generated voltage being in the opposite direction to the applied one. It is a little spiky as the brushes pass from 1 pole to the next. Could this be causing the LEDs to come on in the wrong direction?

The suppression capacitor is there to absorb some of the spikiness. I wonder if this has failed? Have you tried changing it?

[RAF96]

From memory you have to spot drill through the PCB track for various lighting variations. All noted in the instructions.

[Graham108]

23 hours ago, RAF96 said:

From memory you have to spot drill through the PCB track for various lighting variations. All noted in the instructions.

Think that's only for DCC operation via a chip.

[Graham108]

On 23/11/2020 at 14:25, Pete the Elaner said:

I've not had this problem but I am trying to think of what may be going on.

A motor is also a generator, with the generated voltage being in the opposite direction to the applied one. It is a little spiky as the brushes pass from 1 pole to the next. Could this be causing the LEDs to come on in the wrong direction?

The suppression capacitor is there to absorb some of the spikiness. I wonder if this has failed? Have you tried changing it?

What's a suppression capacitor?

[Graham108]

So here's a photo or 2 - 1 wire runs from the front wheels on the front bogie to one end of the original  bulb - this has been soldered to one side of the PCB ('A'). Another wire runs from the rear wheels on the front bogie to the motor - a wire from the rear bogie is also linked to the motor. A wire then runs back to the other side of the original bulb - this has been soldered to the other side of the PCB ('B'). The diode originally in this wire has been removed and the 2 ends soldered together.

 

Hopefully the pictures show all this - any help to solve my problem will be gratefully appreciated.

[andyman7]

The wiring from the chassis looks fine - one feed from the motor block, and one from the leading bogie block which will be opposite polarity. How neat is the soldering to the PCB? is it possible that solder is bridging something it shouldn't? I attach pics of a Lima dummy car chassis wired with these showing red and white in operation.

[Dagworth]

Can you try connecting the track feed directly to the motor brushes with crocodile clips and see whether the lights behave then? 

 

Is the problem that both red and white lights show constantly or that they flicker? 

 

What is your controller?

 

Andi

[Pete the Elaner]

3 hours ago, bartram108 said:

What's a suppression capacitor?

 

The component inside the yellow circle.

Since it is your photo I've borrowed to show this, it is obviously physically there. I was wondering if it had failed.

A replacement would cost pennies but it is really not worth placing an online order for, especially as it is just something worth trying.

If you know someone keen on electronics, they may have one or more spare which they will just let you have.

[John ks]

I not sure that this has already been suggested or tried

Remove the brown wire as shown in the picture, this should disconnect the motor from the circuit 

Put the loco on the track & test it 

The motor should not run & the lights should work as expected

if the lights do not work as expected then there is a problem with the lights

If the work OK then reconnect the motor & try again

If the results are the same as the original post then as Pete suggests it could be some sort of back EMF problem or possibly dirty track

On 24/11/2020 at 00:25, Pete the Elaner said:

A motor is also a generator, with the generated voltage being in the opposite direction to the applied one. It is a little spiky as the brushes pass from 1 pole to the next. Could this be causing the LEDs to come on in the wrong direction?

 

 

 

In the last week i have just installed DCC to one of these HST's & when I removed the capacitor I saw that it was held in place by doubling its leads & squashing them against the brush retainers. after time these may become loose

before replacing the capacitor try squeezing the leads against the brush retainer

John

[Graham108]

@andyman7 - as in my original post the dummy cars work fine - although it looks like I've inserted the PCB's the other way up

 

@dagworth - will try your suggestion - probably be tomorrow now - it could be more of a flicker with the 'wrong' lights rather than constant; I'm using a Morley 4-track controller through the hand-held extension

 

@Pete the Elanerthanks I now know something I didn't before

 

@John ks- will try your suggestions if necessary

Edited November 25, 2020 by bartram108
Additional info

[Dagworth]

12 hours ago, John ks said:

If the results are the same as the original post then as Pete suggests it could be some sort of back EMF problem or possibly dirty track

That's exactly what I'm thinking too. 

 

Andi

[Graham108]

So last night I isolated the motor and the lights worked correctly in each direction. So I guess I need to look at the capacitor as the next step.

[delticman]

Did you manage to get this sorted? I have just fitted Black Cat lighting boards to an old Hornby HST on DC and have exactly the same problem as you. The trailer vehicle works fine but on the powered car both white and reds are alternately flickering. The Black Cat instructions state that this could be caused by dirty wheels or track or worn motor brushes, I have cleaned wheels and track but to no avail. I also have a motor bogie that I fitted with a CD drive motor which is very smooth so I might give that a go.

[delticman]

On 24/11/2020 at 18:10, Dagworth said:

Can you try connecting the track feed directly to the motor brushes with crocodile clips and see whether the lights behave then? 

 

Is the problem that both red and white lights show constantly or that they flicker? 

 

What is your controller?

 

Andi

As usual Andi you are spot on. I connected croc clips directly to the motor and the lights behaved. I thought the wheels were clean ( I had used Isopropyl Alcohol) but I suppose on an over 40 year old model the grime must get ingrained so out came the rotary wire brush in the Dremel and hey presto, it all worked fine! Thank you sir.

 

Geoff

[Graham108]

@Deltic Man As an interim fix, and as my layout is round & round with the loco always at the front, I just put some black  tape over the red LED's. However thanks for the solution that worked for you - I'll look to clean the wheels next time I'm running the 125's (I have too many trains so they don't get run very often).

 

Graham