H&M Powermaster transformer/controller (blown capacitor)

I would recommend a polypropylene axial capacitor, like:

Polypropylene caps are rugged and self-healing. The only issue is their max temp of 105C which I hope isn't going to be an issue.

Having a rethink, without knowing more about the device I'm not certain this cap does any more than noise suppression and it's failure may be a red herring. Best check the transformer first or the fuse if there is one.

In message <qpmfm4$4n6$ snipped-for-privacy@dont-email.me, Fredxx snipped-for-privacy@nospam.com writes

Interesting, thanks. Yes, the fuse in the plug blew, so it would be OK to remove the blown capacitor then reassemble, fit a new fuse in the plug and test the output with my trusty analogue multi meter?

Assuming the cap really is only noise suppression, it may not even warrant replacement?

yes

and if so, what?

Yes.

yes

I still would.

Thank you. I wondered afterwards whether noise referred to interference with TVs and radios, or noise as in voltage stabilisation.

The former, although not necessarily very effective. If as it appears this capacitor is across the mains[1] then you should get one specifically rated for this service and preferably the same value (0.1 microfarad). This is generally called an X rated capacitor, suitable for mains filters at 240v, in the description But they are fairly cheap and reliable if from a reliable supplier.

Fortunately I think it is fairly likely that failure of this capacitor caused the original fault.

Graeme wrote on 03/11/2019 :

Noise as in interference to TV and radio, from the train's poor contact with the track and commutator noise.

In message <qpmrmv$f81$ snipped-for-privacy@dont-email.me, Harry Bloomfield <?.?@NOSPAM.tiscali.co.uk.invalid> writes

Thanks Harry. That was my initial assumption, mainly because many locos sold in the 50s (think Hornby Dublo) had a wax capacitor across the centre rail pickup.

It's a paper 0.1uF 750v. The high v rating suggests it's across the mains, in which case replace it with a 0.1uF X2 type cap, they're generally rated to 275v ac. It ought to work ok without the cap.

The unit also has a metal rectifier by the look of it. I hope it's not selenium... :) Best power it up outdoors.

NT

Should be enough,[1] yes, but at this point in the cirtuit - mains input

- a capacitor specifically rated as a mains filter capacitor should be used.

It looks like that was just a mains filter cap. If it was across the mains (as its working voltage would suggest) then it may have failed short and taken out the plug fuse when it failed. If you chop it out, replace the fuse and re-test then chances are all will be well.

You can then replace it with a modern mains input suppressor - these normally have a 0.1uF cap in series with a 100R resistor, like:

Sorry! the EU confused me:

I can't see a proper earth on that thing.

Gaugemaster do nice new ones with a lifetime warranty. I bought a s/h four channel one with one faulty channel and sent it back and they repaired it without question.

The earth is soldered directly to the side of the transformer.

Gaugemaster are good, but not enough amps for 0 gauge. Bench power supplies are great, 0-20v (some 0-30v), up to 5 amps. The Powermaster supplies 0-12v up to 2.5 amps, which is plenty for most locos, and far more than a Duette or other, similar, later models.

the guagemaster do 2.5A

I'll investigate - thanks.

Got the Powermaster reassembled today, after unsoldering and removing the blown capacitor. Good job I took plenty of pictures!

New 3A fuse and yes, it powers up. Checked output with multi meter and all as expected. Left sitting on but with no load for 3/4 of an hour, then used for 5 minutes, drawing about 8v, 0.6 amps. Case slightly warm, as usual, and the usual mild electrical smell, but nothing untoward.

Success! Thank you, all! Two more to investigate, now.

the cheapest option is the panel mounting controllers and a toriodal transformer from somewhere like cpc.

the cased gaugemaster controls are quite expensive.

IIRC an O gauge panel is about £60 and the same thing in a case with transformer about 200.You could buy a 20A 12V PSU of ebay and a 10A buck converter to modify modify (replace the 10 turn pot with a normal one) for about £20 the pair.

In message <ZAawF.1798$ snipped-for-privacy@usenetxs.com, "dennis@home" snipped-for-privacy@invalid.invalid writes

Far and away the most popular option among users today is a unit made by Circuit Specialists Europe :

I have one, and a similar unit from Maplin, and both work extremely well, but are similar in price to Gaugemaster and others, which is why I am trying to use old Powermasters, often available for a fiver.

Many locos, particularly modern production, don't need the power of the bench units, so, with a patch panel and 4mm banana plugs, matching controller to loco is straightforward. The built in volt and amp meters in the bench units are useful, as some locos date back to accumulator days, requiring only 4 or 6v, but a lot of amps.

The problem with those is they current limit and not trip on a short. This means there could be enough current flowing to do some damage if you don't notice and turn it off quick.