Defective 51070 (5A Controller) - Stuck in Boost Mode

[LittleRedTrain]

Hi all,

I just picked up an LGB 51070 (5A Controller) cheaply off eBay. It was sold as spares/repairs but I thought I'd have a punt as at the very least, it could provide spares for my other one.

Upon testing, it appears that it is stuck permanently in 'Boost Mode', i.e. sending full power to the track regardless of the setting of the control knob.

Has anyone had anything similar, and if so, how did you fix it?
Also, what's the easiest way to get inside one of these units? There don't appear to be any obviously visible screws (though I haven't investigated it too closely yet).

Thanks in advance for any tips.
Regards
Daniel

 

[nicebutdim]

Afraid you have to pop out the little plastic rivets around the base. They're not reusable, I just put small screws in after. Be careful as you take it apart, note where the bits go as you take the top off as the buttons have springs that tend to fly off during the process. It could be a case that the microswitch has failed that is worked by the button. Try un-soldering the contact that would be normally closed when the button is depressed and test again.
The knob itself also has a finger spring that will escape when fiddled with.

 

[LittleRedTrain]

Many thanks that's really useful, especially the warning about the springs!

Probably won't get a chance to look at it today as I've got to prepare for 14 people invading my one bedroom bungalow.

 

[dutchelm]

The easiest way to get the little red plugs out is to drill a small hole in them. Then you can screw in a small screw a few turns & pull out the plug. It can then be reused.

 

[LittleRedTrain]

Well, I managed to get it apart and test it today (with help from my Electronic Engineer mother).
The Boost microswitch seems to be functioning correctly and we couldn't see any other obvious faults (shorts, burnt components etc), so it looks like the problem might be more serious.

Does anyone know whether I'd be able to get this serviced by LGB (or Massoth?) and what the likely cost would be?
Is there a service agent in the UK?

Thanks
Daniel

 

[Tim Brien]

Daniel,
I had the signal box version of this controller. It suffered the same fate after I accidently shorted out the power leads (full power at all times). Obviously, I fried the onboard electrics. The signal box is now a non-functioning building gracing my railway.

 

[vasim]

LGB Controllers are junk. I bought a brand new one, worked fine but then had a derailment. The electronics inside fried and that was the end of that.
When opening (as described in previous posts) I found all sorts of unnecessary electronics inside, none of it available from LGB as spares. Surely only a simple potentiometer is needed, and what happened to the safety cut off switch? LGB seem to make things over complicated for the sake of it.
Needless to say, it was £100 down the drain and I replaced it with a Maplins Bench Power Supply Unit for £50 http://www.maplin.co.uk/bench-power-supply-with-lcd-screen-219129 which has proved to be far better. I know of two others who had the same problem after a derailment.

 

[funandtrains]

These controllers do have a reputation for going wong if you want analoue the Aristo-Craft version is better value, having said I have one of the LGB ones and it has not caused a problem.

 

[vasim]

These controllers do have a reputation for going wong

Is that just the Chinese made ones ?

 

[Brixham]

The 2 amp versions of the controller use readily available components, a few resistors, a couple of low power transistors, and a high power transistor in a simple voltage regulator circuit. Complicated by the boost, and reversing microswitches.

From a brief inspection of the gubbins some time ago, the 5 amp controller is a switching device. It does have built in protection, as any minor short causes a shut down, to restore the power, the controller has to be reset to 0, and then power increased. Repairing one of these units is tricky without a circuit diagram or parts list. However, as yours is faulty, you have nothing to loose by replacing the 'switching' component of the circuit. This is likely to be a 3 legged power device in series with the inductor mounted on a small heatsink. I suspect that is has failed 'short circuit', giving full power at all times. A quick way to prove this is to snip all 3 legs, and then there should be no output. Then read the product data on the device, and google a replacement, which would be unlikely to be more than £2-3.

If all else fails, a month or so ago GRS had a 5A chassis mount controller which would be a replacement, think it was £50ish.

Good luck....I too saw this on an internet auction site...but decided against it as I already have too many 'projects'!

Malcolm

 

[LittleRedTrain]

Thanks folks. As mentioned, without a circuit diagram, trying to do any kind of repair of the 'clever bits' is going to be a nightmare, which is why I was interested to know whether there was any chance of getting it professionally serviced.
The switching component is a MOSFET I think, so replacing that might be a possibility.

I mainly wanted the 51070 so I could use it for wireless operation with the handlheld remote etc. It's unfortunate that LGB don't do a box which is just wireless-only, unless you are using MTS.

 

[alecescolme]

I mainly wanted the 51070 so I could use it for wireless operation with the handlheld remote etc. It's unfortunate that LGB don't do a box which is just wireless-only, unless you are using MTS.

Have you looked into the Aristo TE, I personally see no reason for buying LGB.

Alec

 

[matthew]

I replaced it with a Maplins Bench Power Supply Unit for £50 http://www.maplin.co.uk/bench-power-supply-with-lcd-screen-219129 which has proved to be far better. I know of two others who had the same problem after a derailment.

We use 2 of these bench supply's ourselves, they're great, especially when they were on offer at £50 as you said.

 

[Zerogee]

These controllers do have a reputation for going wong

Is that just the Chinese made ones ?

"Two wongs don't make a wight...."

 

[LittleRedTrain]

Have you looked into the Aristo TE, I personally see no reason for buying LGB.

Alec

I've got a (very old) TE, which is my backup. However I much prefer the traditional dial offered by the LGB 55016 rather than the 'faster/slower' buttons of the TE.
Also, I already have a working 51070/55016 combo set up, this one was to be for a second controller.
It also future-proofs me if funds ever permit me to go down the MTS route.

As I said, it was just a punt, and I knew there was a fair chance it might not work, so I'm not overly upset.