H & M Powermaster controller

[sagaguy]

My 50/60 year old Powermaster has finally let me down,locos will run bacwards but not forward.I suspect it`s the rectifier as these are a variable transformer unit & the track supply is rectified on the supply to the terminals.I`m not certain of the rating of the rectifier to replace it with a modern equivelent,can any one help?.

 

 

                               Ray.

[PatB]

I don't know the rating of the original H&M rectifier but I would have thought that something like this or a locally available equivalent would be more than beefy enough for the job.

[Il Grifone]

IIRC fom the last time I opened mine, there is a selenium (or copper oxide?) finned bridge rectifier on the RHS. Since the unit has 'Variwave' rectification four separate diodes will be necessary for a replacement - Anything with a rating of 100 V @ 5A or more will do. (IIRC the unit is rated at 3A, but overkill won't hurt).

 

However rectifier failure (usually accompanied by a strong smell with these types of rectifier) would result in permanent half wave output, which would result in slow running. The reverse function is carried out by switch contacts on the control knob and it is probably these that have failed. With luck, they just need cleaning and/or adjustment.

 

In the worst case a separate reversing switch can be installed using a DPST switch, though this is not ideal IMHO.

 

Ensure the unit is unplugged from the mains before opening the case. I believe modern regulations would require the case to be secured with rivets and not screws to prevent, or at least hinder, access.

Edited January 16, 2017 by Il Grifone

[sagaguy]

Thanks Griff,no smell or burning,i shall investigate the reversing switch,good job i have another controller,Hornby dublo locos need a good supply of amps to make them run properly as they age.To replace it,i think the Gaugemaster 2.5 amp for 0 gauge would be preferable to the 1 amp outputs of my WW handheld units.

 

                       Ray

[5050]

Great controller.  I always lusted after one when I was a lad - and now I have one!

 

It's tucked away in a drawer along with other 'collectable' controllers but I would dig it out and use it if the situation ever arose.

[hayfield]

My 50/60 year old Powermaster has finally let me down,locos will run bacwards but not forward.I suspect it`s the rectifier as these are a variable transformer unit & the track supply is rectified on the supply to the terminals.I`m not certain of the rating of the rectifier to replace it with a modern equivelent,can any one help?.

 

 

                               Ray.

 

 

Ray

 

Could it not be the mat (no idea what its called) with the wire wound around it, on the inside behind the control knob, if it works one way it should work the other. I would guess its a bad or loose connection. Failing that if the mats are the same, buy a cheap control panel mat and get it fitted by a competent person

[Il Grifone]

Even suffering from old age, Dublo locos shouldn't draw more than about 600 mA.  Most Dublo power units were rated at 9VA - 750mA. If they draw more they will tend to overheat. The usual causes for this are excessive brush tension, crud gumming up the gears and bearings and/or a tired magnet. A faulty armature is also a possibity.

[sagaguy]

IIRC fom the last time I opened mine, there is a selenium (or copper oxide?) finned bridge rectifier on the RHS. Since the unit has 'Variwave' rectification four separate diodes will be necessary for a replacement - Anything with a rating of 100 V @ 5A or more will do. (IIRC the unit is rated at 3A, but overkill won't hurt).

 

However rectifier failure (usually accompanied by a strong smell with these types of rectifier) would result in permanent half wave output, which would result in slow running. The reverse function is carried out by switch contacts on the control knob and it is probably these that have failed. With luck, they just need cleaning and/or adjustment.

 

In the worst case a separate reversing switch can be installed using a DPST switch, though this is not ideal IMHO.

 

Ensure the unit is unplugged from the mains before opening the case. I believe modern regulations would require the case to be secured with rivets and not screws to prevent, or at least hinder, access.

 

It was the reversing switch that caused the problem,for some reason the P/B contact lost contact with the switch disc & had to be bent back to the correct position!!.All seems OK now.

 

 

                               Ray.

[sagaguy]

Ray

 

Could it not be the mat (no idea what its called) with the wire wound around it, on the inside behind the control knob, if it works one way it should work the other. I would guess its a bad or loose connection. Failing that if the mats are the same, buy a cheap control panel mat and get it fitted by a competent person

 

Powermasters are a different animal to their other controllers,they have a wiper that moves across the transformer windings(Variable transformer) & appears to rectify the voltage to the output terminals.These really were Quality products,still going strong after 40/50 years & will probably still be working when solid state units have given up the ghost.

 

                                                       Ray.

Edited January 17, 2017 by sagaguy

[Il Grifone]

The variable transformer technique ensures the source impedance of the power supply is as low as possible giving good control of the motor. It is possible to simulate this with electronics, but the simple mechanical method works well and is very reliable.

 

I have a Hornby electronic controller* that has failed but it's only a quarter of the age of my Powermaster. There's not much in it - a couple of semiconductors, so it shouldn't be difficult to fix.

 

* I've read these are feedback controllers but there's no sign of any feedback circuitry

Edited January 17, 2017 by Il Grifone

[Southernman46]

Powermasters are a different animal to their other controllers,they have a wiper that moves across the transformer windings(Variable transformer) & appears to rectify the voltage to the output terminals.These really were Quality products,still going strong after 40/50 years & will probably still be working when solid state units have given up the ghost.

 

                                                       Ray.

Mine is as old as me - 54 and I still use it regularly - great product and I love that the slight smell of "burning electrickry" it produces

[GoingUnderground]

I always liked the idea of the Powermaster, but using Triang catenary, I needed 2 independent supply controllers, and the Duette gave me that. But I still hanker after a Powermaster from the rounded case era.

Edited January 17, 2017 by GoingUnderground

[sagaguy]

It`s certainly more durable than an ECM Compspeed controller with walkabout that i bought in the late 1970s.it gave up the ghost about 2 years after i bought it & by then,ECM had gone out of business.I never did find anyone who could repair it.It wasn`t cheap either.

 

           Ray.

Edited January 17, 2017 by sagaguy

[Il Grifone]

It`s certainly more durable than an ECM Compspeed controller with walkabout that i bought in the late 1970s.it gave up the ghost about 2 years after i bought it & by then,ECM had gone out of business.I never did find anyone who could repair it.It wasn`t cheap either.

 

           Ray.

 

Perhaps the two occurrences are not unrelated.  

 

The Powermaster is rather built on heavy engineering principles and near indestructible.

[Titan]

The variable transformer technique ensures the source impedance of the power supply is as low as possible giving good control of the motor. It is possible to simulate this with electronics, but the simple mechanical method works well and is very reliable.

 

I have a Hornby electronic controller* that has failed but it's only a quarter of the age of my Powermaster. There's not much in it - a couple of semiconductors, so it shouldn't be difficult to fix.

 

* I've read these are feedback controllers but there's no sign of any feedback circuitry

 

Was it an R965? Gets a good review here, along with an assessment of other types of controller:

 

http://www.scottpages.net/ReviewOfControllers.html

[kevinlms]

It`s certainly more durable than an ECM Compspeed controller with walkabout that i bought in the late 1970s.it gave up the ghost about 2 years after i bought it & by then,ECM had gone out of business.I never did find anyone who could repair it.It wasn`t cheap either.

 

           Ray.

ECM ground off the chip numbers, making it difficult to copy/repair the circuit. All gone with the late owner now.

[5050]

ECM ground off the chip numbers, making it difficult to copy/repair the circuit. All gone with the late owner now.

Don't I know it!  I've got 2 used ones that have 'retired from service' and a NOS one I bought at Manchester Ex. 2015 still wrapped in its box - and this doesn't work either!  All are the Rambler version which I really liked for delicate shunting control, ideal for a small shunting plank.

[Il Grifone]

Was it an R965? Gets a good review here, along with an assessment of other types of controller:

 

http://www.scottpages.net/ReviewOfControllers.html

 

That's the one!. I understand there are different versions. I saw an article on how to beef one up, but it only applied to pre 1995 controllers. Since mine is dated 1999, I didn't bother too much.... One day I'll get around to repairing it.

 

The article also shows the insides of a Powermaster.

[sagaguy]

That's the one!. I understand there are different versions. I saw an article on how to beef one up, but it only applied to pre 1995 controllers. Since mine is dated 1999, I didn't bother too much.... One day I'll get around to repairing it.

 

The article also shows the insides of a Powermaster.

That picture is of a later Powermaster with Variwave slider control,mine are the earlier models.

 

                         Ray

[Il Grifone]

Yes the later ones have thermal cut-outs. The variwave was an optional extra IIRC and replaced the half wave/full wave switch with a substantial wire wound variable resistor. The option may not have been available on the early ones? Removal of the cut-out button, switch and lamp clears a lot of clutter from the panel.

 

I did find mine wasn't giving the full output voltage. This was due to the slider on the transformer not completing its traverse. A little judicious bending of the robust, but rather crude, lever mechanism cured this problem. Replacement of the obsolete rectifier with silicon diodes would help too, Selenium or copper oxide rectifiers have a voltage drop of 2-3 volts, which is why they require fins and/or a heat sink.

 

Germanium diodes have an even lower voltage drop, but are not easy to find these days. Their relatively high reverse current makes them unsuitable for many uses. (There are some on eBay, but they are quite pricey.)

Edited January 19, 2017 by Il Grifone

[roythebus]

I had one of the "intermeiate" angled box Powermasters. The levers for the reversing mechansim fell apart and shorted out the transformer so it got scrapped years ago.it was one of those with the slider type vari-wave control too. 

[brigo]

ECM ground off the chip numbers, making it difficult to copy/repair the circuit. All gone with the late owner now.

 

Chip is a CMOS 4001 Quad NOR gate. I worked out the circuit diagrams of the Compspeeds and Rambler Minor many years ago when I was given some to repair.

 

Brian

[rodent279]

I have an H& M Powermaster, which has been dropped several times, and still worked. Not anymore though, something is causing it to go from 0 to 18V as soon as the knob is turned. Has anyone ever come across a wiring diagram? I know they are pretty simple, and I class myself as competent in these things, but it would be nice to have one. Saves me having to trace it out!

[kevinlms]

1 hour ago, rodent279 said:

I have an H& M Powermaster, which has been dropped several times, and still worked. Not anymore though, something is causing it to go from 0 to 18V as soon as the knob is turned. Has anyone ever come across a wiring diagram? I know they are pretty simple, and I class myself as competent in these things, but it would be nice to have one. Saves me having to trace it out!

I've never seen a circuit. A couple of websites claim to have one, but they don't work!

 

Perhaps eBay for another? There must be plenty around, because in Railway Modeller 1958 November, it was claimed that 10,000 were made in the first 12 months of production!

[Dublodad]

From memory, the Powermaster is a Variable Transformer controller that uses an Auto transformer to give an infinitely variable output from the transformer, rather than a "stepped" output. Perhaps the "slider" has jammed, but this doesn't make sense!!!!

Open it up and have a look!! then trace the circuitry.

 

Terry