DIGITRAX DS74 PROBLEM

[TEAMYAKIMA]

I regret that I am still getting problems with DIGITRAX (in general) even though tens of thousands of people around the world rave about the brand.

 

Specifically today with a DS74.

 

I bought a DS74 a couple of months back when I had hoped to buy a DS64 - only to discover that they are discontinued. So I tried the DS74 and found it just didn't produce enough power to throw a crossover using two PECO points. At that point (no pun intended) I was desperate, as my next show was only days away and when I found a UK dealer with stock of DS64's I bought one and just forgot about the DS74.

 

Last week I needed to resurrect the DS74 and sure enough it just made the PECO point motors twitch - and not throw. So I spoke to the dealer who sold it to me and he asked me to send it back. I did and he replaced it. Before sending it to me he tested it with two PECO points fitted with PECO point motors and sent me a video of it firing them successfully - and YES, he did activate the internal upgrade 'for sticky motors'.

 

The new DS74 arrived yesterday and I fitted it today - and on test it most often didn't produce enough power to fire one PECO point let alone two.

 

I phoned the dealer, who is VERY good with regards to customer service and I explained that the unit which worked perfectly in his shop wasn't on my test bed - just one fiddle yard board with three points. We spoke and I told him that I was powering it from my 12volt DC bus and he thought that must be the problem as he was using a DIGITRAX PS-14 which deliver 14.9 v DC.

 

We left it there, but I have now looked at the DIGITRAX instructions and it says 'any DC power source from 10v to 22v'.  So, on that basis my 12v DC should be OK. The instructions then confuse matters somewhat when they seem to say that you can power the DS74 with 10v to 22v OR track power which implies that track power is an alternative, but the diagram shows the DC power going in with no comments , but the track is shown as OPTIONAL which would imply that it is an optional addition, not an alternative.

 

So, what are people's experience? Does the 12v power source (as opposed to 14.9v) explain the problem?

 

Would replacing the 12v Dc power input with track power improve matters?

 

I need to understand DIGITRAX's mindset, because at the moment I am so depressed/deflated by the constant problems I seem to have with this brand. 

 

 

[kev]

I would put it on a separate power supply

 

[peach james]

I too would recommend a separate power supply, pain in the back side that it is.  I would suspect that it is using a voltage multiplyer internally to charge the capacitors.  Might a pair of ds52s work?  (And they do charge off track).  Or can you find any NOS DS 64’s?  ( no, I don’t have one…my spare is running my floor level N layout)
 

TBH, I use torti for the most part. 
 

James

 

[TEAMYAKIMA]

2 minutes ago, peach james said:

I too would recommend a separate power supply, pain in the back side that it is.  I would suspect that it is using a voltage multiplyer internally to charge the capacitors.  Might a pair of ds52s work?  (And they do charge off track).  Or can you find any NOS DS 64’s?  ( no, I don’t have one…my spare is running my floor level N layout)
 

TBH, I use torti for the most part. 
 

James

 

 

Hello James

 

Thanks for that - yes it would be a pain. Being an exhibition layout, the more things we have to plug in or set up, the more the time taken.

 

The confusing/annoying thing is that DIGITRAX say 10v to 22v and, in that sense, I have complied with that. What do you think about feeding it with track power? In addition to 12v, or instead of 12v?

[WIMorrison]

The key to this is the type of turnout motor that you are using and also the weight of wire that is between the decoder and the motor.

 

The Peco/Seep motors are incredibly power hungry compared to almost any other style of motor and few decoders can provide sufficient power to shift them consistently without the addition of CDUs. I think that the DCC Concepts ADFX units are one of the few decoders that will do this reliably.

 

if the wiring is too light then you will also have issues switching, and finally the alignment of the motor with the tie bar is critical, the slightest misalignment can be sufficient to cause these motors to stall, especially when the power supply is inadequate. 
 

finally, on power supplies it is not the voltage that is important, it is the power available which is the factor that decides whether it will work. 

[Nigelcliffe]

1 hour ago, TEAMYAKIMA said:

The confusing/annoying thing is that DIGITRAX say 10v to 22v and, in that sense, I have complied with that. What do you think about feeding it with track power? In addition to 12v, or instead of 12v?

 

Volts input are likely to relate to volts out of the device.   So more volts in will give more volts out.     If the motors need more volts to move, then you'll have to put more volts in.  

 

Track power (alone) may show you that more volts is the answer (if you don't have a 15v or 18v power source around for testing), but its not something I'd use for exhibitions on a large layout: keep track power for powering the track.   

 

 

Once you have solved the input voltage issue, then there are devices which can multiply input voltages.  So, 12v input and more volts out.   Pololu is one manufacturer of such devices.    That may be a solution if your layout supply is 12v: fit a voltage multiplier next to the DS74's. 

 

 

( To Iain's comment on CDU's - the DS74 is supposed to have one, it is enabled by a setting in the DS74's op-switches.   I've not used a DS74, and I don't use Peco point motors, so can't comment on how it works in practise ).  

 

 

  

- Nigel

[TEAMYAKIMA]

6 minutes ago, Nigelcliffe said:

 

Volts input are likely to relate to volts out of the device.   So more volts in will give more volts out.     If the motors need more volts to move, then you'll have to put more volts in.  

 

Track power (alone) may show you that more volts is the answer (if you don't have a 15v or 18v power source around for testing), but its not something I'd use for exhibitions on a large layout: keep track power for powering the track.   

 

 

Once you have solved the input voltage issue, then there are devices which can multiply input voltages.  So, 12v input and more volts out.   Pololu is one manufacturer of such devices.    That may be a solution if your layout supply is 12v: fit a voltage multiplier next to the DS74's. 

 

 

( To Iain's comment on CDU's - the DS74 is supposed to have one, it is enabled by a setting in the DS74's op-switches.   I've not used a DS74, and I don't use Peco point motors, so can't comment on how it works in practise ).  

 

 

  

- Nigel

 

Nigel

 

As always, many thanks.

 

I was asking these questions, because I wanted to be cautious before doing anything, but I will now try the track power idea as you have endorsed it.

 

As regards the CDU, I asked my dealer to activate it when he was testing the replacement and so I assume that it has been activated. 

 

 

[AndrewC]

A couple of other points. (pun intended) 

 

1: are the points wired in parallel or series? If they are always going to be thrown in pairs, then wire them in series. That's why the Peco motors isolate each coil. 

2: yes more oomph from the power supply. You may have enough voltage but do you have sufficient current. 12v with a 2a output is better than 19v with a 0.5a output. 

3: how stiff are the motors and the point spring? When I used to use solenoid motors, I found that a bit of light oil on the moving parts of the motor as well as backing off the point spring to reduce the tension worked well. Have you tried throwing 2 points from the unit on your bench? If that works it is likely the points themselves are too stiff. 

 

As in the pic below a screwdriver is used to increase the distance between the tie bar and the spring retention clip. This reduces the force needed to throw the point but at the same time retaining the spring's function to keep the point blades pushed against the rails. 

 

[Uksid]

I have a DS74.  I’m not impressed.

 

When I bought it new it wouldn’t throw a Peco Pl10 at all, even one dangling in the air, not attached to a set of points.

 

I’m in the US, so Digitrax had me send it to their Florida HQ for repair.  Now it’s back it just manages to throw the points, but it’s only just!  I’m using it with a Digitrax 14v PSU the internal CDU switch is on.

 

I won’t be buying any more of these.  I managed to get a DCC concepts decoder (a little difficult here in the US) but it is way better than the Digitrax.