Gaugemaster Combi: re. slow running

[philsandy]

My layout is DCC but I have a DC controller to test new locos before fitting the decoder. For this purpose I have a second hand Graham Farish (AGW PE860) bought from my local model shop a couple of years ago.

It works OK but I can not achieve slow running with it, I put this down to it being an old controller, so I've bought a new Gaugemaster Combi after reading good reports on here, but it is no different.

The loco will not begin to move till the throttle is at 20 (range is 0-100), it is slow speed, but not at a constant rate, increase it to 22 and it is a smooth constant speed, but far too fast for shunting. Anything over 50 is just ridiculously fast.

There is just no fine control at the lower end, it seems to be all or nothing.

 

Is it faulty, or is it what I suspect, a basic "Train Set" controller.

[DCB]

The Loco?   Have you tried more than one loco because it sounds more like a faulty loco than a faulty power unit or two

[philsandy]

Hello Phil,

 

I would suspect the controller 80% and 'maybe' the loco 20% I think the controller is one of the two transistor variety with a pure DC output.

 

The GM 'UF' controller with both PWM and Feedback will give you the finest slow speed control possible.

 

If you would lie to make your own the circuit can be found here: http://www.scottpages.net/ReviewOfControllers.html scroll down the page to see the circuit. Replace the obsolete D13T1 with 2N6027 and the 10k preset with a single 22k resistor. 

 

Cheers - Jim

Thanks Jim,

Do you mean by replacing the 2 components it will convert the Combi to a UF model?

Excuse my ignorance, but I'm not electrical, what is a 2N6027? and is the other mod replacing a 10k resistor with a 22k resistor?

[philsandy]

The Loco?   Have you tried more than one loco because it sounds more like a faulty loco than a faulty power unit or two

Yes David I have. Tried several with the Graham Farish controller, and 2 locos with the Gaugemaster, none will run at slow speed.

[H2O]

Just looked up the 'replacement' unijunction transistor but I can only find it on the Farnell website and then only as no longer stocked or no longer manufactured! :-(

 

http://uk.farnell.com/search?st=2n6027

 

Looking up unijunction at Farnell gives 2n4870 and 2n4871 (as well as the obsolete 2n6027), are either of these suitable replacements?

 

http://uk.farnell.com/search?st=unijunction

[Junctionmad]

The 2N6027 is still available , try findchips.com , mouser and diigikey have stock 

 

this is whats listed as a replacement for that device 

 

2N6116

2N6119
MPU131
MPU231
SK3628

 

 

but some of these are just as rare or rarer 

 

 

NOTe that  aliexpress.com has 2N6027 available , 50 for 7 quid or there about !!!!

Edited November 6, 2017 by Junctionmad

[cpman46]

Just looked up the 'replacement' unijunction transistor but I can only find it on the Farnell website and then only as no longer stocked or no longer manufactured! :-(

 

http://uk.farnell.com/search?st=2n6027

 

Looking up unijunction at Farnell gives 2n4870 and 2n4871 (as well as the obsolete 2n6027), are either of these suitable replacements?

 

http://uk.farnell.com/search?st=unijunction

If you are looking for one or two 2N6027 PM me with your address and I can put them in the post.

Mike

[clickertyclack]

Found this listed as a equivalent to the 2N6027 on RS.

 

http://uk.rs-online.com/web/p/ujt-transistors/2508963555/?searchTerm=NTE6402&relevancy-data=636F3D3126696E3D4931384E53656172636847656E65726963266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E2E2A2426706F3D31333326736E3D592673743D43415443485F414C4C5F44454641554C542673633D592677633D4E4F4E45267573743D4E544536343032267374613D4E54453634303226&dym=nte640

 

Hope of interest

 

CC