hornby point motor moves point only one way

[midway]

I have six point motors fitted through a hornby C7024 transformer and into hornby

R965 controler and a CDU. the points are each operated my mini toggle switches and operate okay

apart from one which pushes but will not pull.I have changed the motor

 

with no success,I hasten to add the point works very freely by hand and the motor seems to change okay when not

attached to the point.I wonder if I change the supply to a ac transformer giving an output

of 25v at say i.5 amp and doing away with the

 

Controller would solve the problem and give more

power to the points?

[Flashbang]

Hi

As you're using a CDU ideally the input wants to be ac. 16 volt ac is the norm, but depending on the make of CDU this can be increased to around 24 volts ac.

 

If DC is the chosen input source then it needs to be ideally between 19 and 24 volts

 

dc.

 

Current from the PSU regardless of power type can be as low as 250 milliamperes, but a higher current output will recharge the CDUs capacitors quicker.

 

To note; the reason an ac input to a CDU is preferred is because the CDUs capacitors charge

 

to 1.4 times the measured ac input volts. I.e. they charge to the ac Peak voltage value not the RMS value which is the voltage normally referred to and measured.

 

[Flashbang]

Also to add... All wiring to and from the point motors (3 wires) and the output from the CDU to the switches should be in 16/0.2mm equipment wire or a larger wire size.

[midway]

Hi flashbang, thanks for info but what is "psu" and as I am dcc is there any need for using

the hornby controller or can I go straight from transformer to cdu (gaugemaster).finaly do I need

a 16or25V transformer. Thanks,midway.

[Fishmanoz]

PSU - Power Supply Unit.

 

The usual reason for a motor firing only one way is poor alignment to the point or the whole thing not being perfectly flat. Make sure the motor is not screwed down too tightly and, if not flat, use a little packing under

 

motor or point to make it flat. This is most critical with surface mount motors. And check it is in the correct position with respect to the point.

[Fishmanoz]

And given all your others are working OK, it tends to indicate the power supply to them is OK. However, if this one happens to be furthest from the supply of them all, then too light a gauge wire may be a factor as Flashbang suggests.

[Gregd99]

I suggest lifting the push bar away from the point motor and checking if the motor fires both ways.

 

If it does then the electricals are OK and it is probably an issue with alignment of the motor and the points.

[Fishmanoz]

Greg, he's already told us this works, hence the alignment being the issue.

[Gregd99]

Fishmanoz said:

Greg, he's already told us this works, hence the alignment being the issue.

oops - sorry. I should read more carefully.

[Fishmanoz]

No problem, I certainly can't claim to be a careful reader of things myself. Was fortunate to notice this one.

[Flashbang]

midway said:

Hi flashbang, thanks for info but what is "psu" and as I am dcc is there any need for using
the hornby controller or can I go straight from transformer to cdu (gaugemaster).finaly do I need
a 16or25V transformer. Thanks,midway.

Hi
As

I said in my post 2 & 3 above.. Ideally the power supply to a CDU (Capacitor Discharge Unit) needs to be 16 volts ac or 19 to 24 volts dc from the power source.

The Elite and Select both offer a 15 volt dc output. This is really on the low side

for solenoid point motor operation and will not be increased by using a CDU.
So for example... dc in to a CDU at xx volts equals dc out at the near same xx volts. But ac in at 16 volts equals approx 22.4 volts dc out, 24 volts ac in equals approx 33.6

volts out, less some minor losses due to the rectifaction of the ac by the CDU.

I would initially try doubling up or completely replacing all three wires to/from the point motor with a larger size of wire, plus double up or replace the wire from the

power supply to the point operating switches. As stated previously in my posts the minimum wire size needs to be 16/0.2mm equipment wire or its equivalent or even a larger wire size which won't hurt. Rule is... too larger wire size wont ever hurt but too small

a wire size will lead to and cause problems!
Remember, you need to be able to get as much of the momentary output pulse from the CDU to the motor as easily and quickly as possible without incurring any or as little wire OHM resistance as possible.

Volt drop due to resistance is your enemy!
:-)