Help with controller fault.

[Clagsniffer]

Hi everyone. I’ve been handed a controller to look at, I’ve no idea why, I can only assume that because I have an interest in model railways that must mean I know how to fix things. I’d appreciate some help if anyone is familiar with the controller in question. It’s a Helmsman Electronics controller, model is MM1/5. The problems with it according to the note are;

 

“speed control not working, running on max speed all the time. Reverse also not working.”

 

Ive attached a couple of pictures. Could anyone suggest a few tests I can do?

 

Thanks.

[kevinlms]

If all else fails.

 

https://peco-uk.com/pages/helmsman

 

It doesn't say which new year.

[lesmond]

These are a beefy controller with enough power to run a Gauge 0 or Gauge 1 controller. Don't plug it in with the lid off unless you really, really know what you are doing (this goes for anything with a mains lead).

 

It sounds as though the mains side of things is ok, but it wouldn't hurt to get this looked at by someone who knows what they are doing to be on the safe side, although it seems to have been PAT tested at some point in its life. This is ok and proves it to be on the day, much like a car MoT, so best to get it checked over.

 

For basic testing of the faults described, with it unplugged from the mains, use a multimeter to test the resistance of the potentiometer / speed control.

 

This should change from low to high as you turn the knob. If it doesn't, its at fault, and will need to be replaced with one of the same value (it has 10K printed on it, so 10K ohms value at full resistance). 

 

Also check the reversing switch (multimeter again) to make sure that it is actually reversing the polarity. It should switch with a good positive click. 

 

Either of these shouldn't be too hard to change if it comes to it, but if you aren't sure about it I can't stress enough to get it to someone who does or give it back with the same advice.

[RAF96]

One of the wires from the reversing switch to the speed control rheostat tag appears to be bent over and touching the component case. Gently bend it upright again. 

 

Edit - there seems to be a lot of hot glue stuff in there. Doesn’t look very professional. At least it has been PAT tested at some time.

Edit again- zooming in on the rheostat shows the tag is well clear. It was just camera angle making it look bent. Getting that earth tag under the bolt when replacing the top will be fun job.

Edited May 28, 2020 by RAF96

[lesmond]

On 23/05/2020 at 16:23, RAF96 said:

One of the wires from the reversing switch to the speed control rheostat tag appears to be bent over and touching the component case. Gently bend it upright again. 

 

Edit - there seems to be a lot of hot glue stuff in there. Doesn’t look very professional. At least it has been PAT tested at some time.

 

Good spot with the rheostat tag. Agreed about the hot glue as well - it doesn't really inspire confidence.

 

Les

[kevinlms]

3 hours ago, lesmond said:

 

Good spot with the rheostat tag. Agreed about the hot glue as well - it doesn't really inspire confidence.

 

Les

Regarding the hot glue gun, looking at the photos most of the blobs seem to be on spade connectors. I wonder if the manufacture has had some warranty returns and it turns out that the spade connectors have fallen out. If that's the case, a cheap insurance policy. As for the blobs on the PCB, probably helps it stop rattling. 

 

I've seen worse PCB designs, where if the device is dropped, the heaviest components (often a coil of some sort), keep going and sheer off the PCB. Thus rendering it useless.

 

Short of the manufacturer drop testing off the workbench multiple times, the design looks not too bad, but room for some minor improvement. 

 

The one thing I don't like at all, is the tight wire which appears to have caused the bent tag! It's hard to be certain, but has that pot rotated slightly?

[lesmond]

14 hours ago, kevinlms said:

 

The one thing I don't like at all, is the tight wire which appears to have caused the bent tag! It's hard to be certain, but has that pot rotated slightly?

 

For the sake on an inch of wire you'd think that there would be some slack. The pot does look to be a little off centre.

[cliff park]

I rather suspect that looking at those pictures is not going to find the fault. Either the OP has the equipment and confidence to get in there and start measuring voltages, or it will have to go to somebody else.