The LNER Encyclopedia

Does anyone else find their layout periodically infested with this menace?

Up until this evening my venerable H&M Duette has been damn near 100% reliable. This evening for no apparent reason it refused to work, or more accurately it would work for 10seconds or 1 throw of a point and then the power would cut out….

I did all the usual, pulled all the connectors out, soldered up any connections that looked loose etc etc, to no success and was just about at the point of admitting that after a half century of service the Duette had died, when for no apparent reason everything started working again….

I still have no idea what the actual problem was!

An obvious case of gremlings infestation, which got me to wondering if anyone else had similar stories of otherwise reliable kit/locomotives/rolling stock suddenly acting up for no good reason?

Jim de Griz

Hi Jim

I've had occasions where a track joiner has started arcing even if nothing has run over it, because of that, the cut out would activate as it would be seen as a short even though there was no direct connection between the rails.

There have also been odd occasions where a switch rail would start arcing while in contact with the respective track rail resulting in a bit of smoke and partial melting of the switch rail but luckily the power cut off in my duette controllable have activated and cut off the power until the problems have been resolved.

The thing I find heavily annoying is that a lot of the time when the problems occur, they are not always immediately evident which can lead to a lot of head scratching and the odd choice words while trying to find the cause.

Despite these odd occurrences, I wouldn't swap my duettes for anything else and if they ever reached a point where they were not repairable, I would immediately begin looking for more duettes to run my layout, best controllers I have ever had.

Jim de Griz wrote: ↑Tue May 21, 2024 10:47 pm Up until this evening my venerable H&M Duette has been damn near 100% reliable. This evening for no apparent reason it refused to work, or more accurately it would work for 10seconds or 1 throw of a point and then the power would cut out…

Start from the mains plug, could just be a loose screw on a terminal, if not then the mains lead, and the lead insulation into the casing, and conmections to the transformer, etc.. And if the device tests fine throughout, try on a different mains socket, and be prepared to call in an electrician. Or skip all the above on the Duette, and hand it to someone authorised to perform a portable appliance test (PAT).

I share your approbation for this most unsophisticated controller, it's my bench test for all new mechanisms; if they run smoothly down to dead slow on this device, then they will 'sing' on a more sophioticated control system such as DCC.

Dont open the Duette, the interior has asbestos therein. I binned mine years ago.

Gaugemaster much much better quality. IMHO.

This thread has got a lot more serious than I intended it to....almost to the point of considering changing the title.

Mersey and Hatfield, thank you very much for your suggestions. Reviewing the work I carried out, I suspect Mersey is right, one of the connections I replaced was probably loose and causing arcing, which was causing the Duette's surge protection to kick in. Turning the power off would have reset the protection whilst eventually I removed and refitted the offending connector by pure trial and error. I still don't know which part exactly was the issue, but I seem to have fixed the problem whilst trying to solve another. Getting the controller PAT tested is something I should have got done by now and would have been my next job, except for Mick's comment.

Thank you for the head's up Mick and a timely comment. In frustration I came VERY close to trying to remove the outer shell last night and only didn't because I didn't have an appropriate tool to hand to remove the rivets. Not expecting to find asbestos, I'm sure I wouldn't have recognised it, but I'd certainly have prodded and poked at it whilst working out how the controller worked....

Given the description of 'Air Flow Resistance Mat' I found on RMWeb and some images from the same, I'm quite concerned. In particular, my Duette has taken a few good knocks in its life and the outer case is slightly distorted, leaving a gap between two of the plates, from an air flow perspective it certainly can't be considered a sealed unit. If the Asbestos has been damaged or become frayed, I'd have no way of knowing.

As much as I hate to get rid of a device that has given Trojan service, and pending some advice from a colleague tomorrow who knows about these things, I think this might be a replacement job.

....real shame if so...

Jim de Griz

Had my H&M units apart on various occasions.

Not convinced of any need for abject panic about undamaged, rigid, undisturbed asbestos-containing materials.

I'd not panic either, and the case can easily be sealed.

Even if a signifcant component for the DC side failed (most likely rectifier or resistance mats) provided the unit is a PAT pass, I would keep using it as a low voltage AC supply. The transformer is a good piece of kit.