H & M Powermaster controller

[rodent279]

Slider looks ok, seems to move correctly. I replaced the rectifier with a silicon bridge rectifier unit about 30 years ago, but it's seen little use since then. I will give it a good clean and see if that improves matters.

[Il Grifone]

It sounds like the bottom end of the variable transformer secondary has gone open circuit. Either the wire has broken or just disconnected itself from its connection. If necessary a turn less should not make any difference, especially since the nominal mains voltage has been reduced from 240 volts to 230 during its lifetime.

 

Basically (from memory it's ages since I opened mine - no need  ) there is the primary winding across the mains (obviously) and the secondary which has a slider contact driven by the control knob which also functions as reversing switch. Tucked up in the RH corner there is a bridge rectifier with large fins. The centre terminal is one pole of the output and the outer two are the other. These are linked via the half wave/full wave switch (or slider on Vari-wave versions*) somewhere in the secondary circuit there is an overload cut-out and De-luxe versions* had a six lever section switch in series with the output.

*IIRC these two features were optional extras but it was rather a long time ago!

[Il Grifone]

On 16/01/2017 at 07:36, PatB said:

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.

 

Fine but overkill!

IIRC the rating is 3A and a 5A bridge would be more than adequate. I have a feeling I used 4x 3A diodes in mine (or it may have been another unit that needed a new rectifier - we are talking ancient history).

A bridge rectifier is only suitable for units without half/vari wave rectification as the switch/rheostat lives in one arm of the bridge.

[rodent279]

11 minutes ago, Il Grifone said:

 

Fine but overkill!

IIRC the rating is 3A and a 5A bridge would be more than adequate. I have a feeling I used 4x 3A diodes in mine (or it may have been another unit that needed a new rectifier - we are talking ancient history).

A bridge rectifier is only suitable for units without half/vari wave rectification as the switch/rheostat lives in one arm of the bridge.

Yes, looking at the bodge-it-&-scarper way I wired in the bridge rectifier, I bypassed the variwave control.

[Sheffield]

I have a Safety Minor, smaller relative of the Powermaster with the same variable transformer arrangement. Excellent unit and I am still useing it.

[roythebus]

Dublodad's reply sounds about right. There is virtually no circuitry in these old units. everything is visible and easily traceable. All the answers are above. It may be the rivets that operate the wiper have broken or failed.

It will take less time to trace the wires in the unit than it will to go online to find a wiring diagram.

 

[cypherman]

Hi all,

Can any one tell me are the H+M Duette controllers a Variable Transformer controller. I have 3 of them and a H+M Clipper controller. I have found them all very reliable. I have few other controllers from H/D and Triang as well. But the do not tend to get out of the box. let alone used.

Edited December 4, 2020 by cypherman

[roythebus]

Duettes are variable resistor, very reliable units. I have one that i bought in the mid 1960s' still using it.

 

[Il Grifone]

IIRC the Duette is two Clipper units in one box. They are variable resistance units, but a cut above the usual variants of these beasts.

They have a switch to select various fixed resistors to match them to different motors (possibly an optional extra?)

I must have one stashed away somewhere, but I have never used it, having a Powermaster and three Dublo Marshall IIIs.

[Bassettblowke]

I used to work in a “bums on seats” university, to those unfamiliar with the term these are former poly techs that used to major in vocational subjects. Hands on engineering, Mates tickets for merchant navy officers etc etc. Many of the old Poly hands resented being elevated to third rate Uni status issuing degrees in tourism and travel and to their minds various other non subjects designed to pull in the paying punters. One such Character I used to meet on occasion was a technician from the electrical engineering dept and in conversation he told me that he started out in life as a TV repairman. Now in the fifties  as a child I well remember the two day wait with a defunct tele waiting for the man in the van to appear, my dad probably inflicted additional damage by administering numerous whacks on the top before resigning himself to forking out for the engineer. In passing I mentioned to him our central heating control panel had gone on the blink and did he think it was repairable, he fixed it in short order and some time later repaired a Marklin transformer for me so this sort of work would be well within the scope of an old school repairman. Only problem is finding one, the local repairman is now an extinct species with modern electronics being consigned to the bin as beyond economical repair as soon as the warranty has expired.

On the Classic O forum there is at least one electrical engineer who is a service agent for both Ace and Darstaed as well as manufacturing his own controllers and a rolling road. It might be worth an enquiry before consigning the  transformer to history or even worse the bin.

[rodent279]

11 hours ago, Bassettblowke said:

I used to work in a “bums on seats” university, to those unfamiliar with the term these are former poly techs that used to major in vocational subjects. Hands on engineering, Mates tickets for merchant navy officers etc etc. Many of the old Poly hands resented being elevated to third rate Uni status issuing degrees in tourism and travel and to their minds various other non subjects designed to pull in the paying punters. One such Character I used to meet on occasion was a technician from the electrical engineering dept and in conversation he told me that he started out in life as a TV repairman. Now in the fifties  as a child I well remember the two day wait with a defunct tele waiting for the man in the van to appear, my dad probably inflicted additional damage by administering numerous whacks on the top before resigning himself to forking out for the engineer. In passing I mentioned to him our central heating control panel had gone on the blink and did he think it was repairable, he fixed it in short order and some time later repaired a Marklin transformer for me so this sort of work would be well within the scope of an old school repairman. Only problem is finding one, the local repairman is now an extinct species with modern electronics being consigned to the bin as beyond economical repair as soon as the warranty has expired.

On the Classic O forum there is at least one electrical engineer who is a service agent for both Ace and Darstaed as well as manufacturing his own controllers and a rolling road. It might be worth an enquiry before consigning the  transformer to history or even worse the bin.

Oh I'm well capable of fixing it. I took it apart and replaced the ailing metal oxide rectifier with a solid state bridge rectifier back in the early 1990's. Looking at the wiring, I bypassed the variwave resistor when I did this, as mentioned above. My original post was to ask if anyone has a wiring diagram, as it would be nice to put it back to original condition, and a diagram would save me having to work it out. It won't go in the bin, it'll be sold, probably for spares or repair as a non-working unit, as the casing is dented, and the screw connector strip on the back is not complete.

I built myself a 0-15v stabilised DC controller while at University, and I've got an H&M 2000, an old Meccano controller, and a Fleischmann controller.

Cheers N

Edited December 13, 2020 by rodent279

[Bassettblowke]

Back in the day H&M operated its own service facility and actively discouraged third party repair thus I think you will struggle to find a  Pukka H&M one, but never say never they must have had some printed for internal use.

[roythebus1]

Maybe the Tri-ang Group if there is one will have them as I believe Tri-ang took over H&M?