I assume it is a transformer similar to that shown on the picture of this link.

If your is intact, then there is a small piece of red plastic in the centre of the turning knob and once that is removed then you'll find a screw to remove the knob.

The link leads to an Internet page and even if it is in German, I believe the picture are helpful.

With John's very sound and wise advice in mind, I'll still try to answer your question.

This is probably your Trafo shown below. The Red knob on these will come off with the top cover, it can only be removed once the cover is off but the knob itself probably no need to remove.

There is a reason for the small silver rivets which is to dissuade the curious. I offer this advice only on the assumption that you are either experienced in electrical work, or will give the information to an experienced appliance service person or electrician to undertake for you - SERIOUSLY!!

Also be aware that the 278a Controller is now very old. ie most likely at LEAST c. 50+ years old so not only have you the issue with the speed control but also the mains flex is very likely deteriorated (internal insulation perished) and should also be replaced.

Couple that with it's relatively low power output and you can quickly see that this is the perfect time to consider replacement and perhaps (if the mains flex is ok) relegate this to being a lighting transformer.

But at the end of the day this forum is an information resource and having serviced a number of these myself I provide the following detail for its information value only;

And with that disclaimer out the way we shall proceed....

The rivets will need to be removed, either cut off or pulled through the holes with small side-cutters. The tabs which protrude through the base mnay be twisted also to secure the top and base together and will need to be gently straightened with flat ('duck-bill') pliers.

Then the top cover can be gently and slowly pried off the base - be careful as the wire for the speed control wiper will remain attached and it's only a short section of wire.

If you are lucky, the wiper may only have lost its pressure against the transformer windings in which case only a gentle bit of adjustment (bending), or in IBM-Speak, 'forming' to give additional pressure.

Failing that, the copper windings may have worn too far for reliable contact in which case repair is simply not an option. It would need re-winding of the core. These are done by machine under specific tension etc etc and impractical to even attempt repair and brings us right back to the 'time to replace it' option.

Hope this helps, and please, once again take this advice seriously - if you don't know what you are doing with main voltage, don't even try. It's just not worth the risk.

Kind regards

Steve
Melbourne

Two quick additions to Steve's excellent advice.

In addition to checking the tension on the sweeper arm, check the wire connecting the dial sweeper to the lug at the back of the transformer. At the dial sweeper end, the wire may be broken or cracked. Even if you cannot see a break, it may have deteriorated within the casing from 50 years of turning. If you are experienced with soldering, de-solder the wire from the sweeper, snip off the end where it is constantly bending, solder on and shrinkwrap a piece of new wire at the end, and solder it to the sweeper arm.

A second point is that when you are through, solidly re-seal the transformer. Replace rivets with rivets, and return tabs to firmly closed position. (In the white transformers install new plugs , wooden dowels sanded down to fit being one possibility.) Definitely re-seal the box, no duct tape!

These things are sealed for a reason, and loose reattachment is an invitation to danger.

I respect the warnings -- indeed incompetent hands and transformers could spell disaster -- but frankly do not see the risk in bending the sweeper to increase tension, or fixing a broken sweeper wire, and then fully resealing the box. Unlikely that I would attempt anything beyond that, however.

Bill

Wow, this sounds like it's more dangerous than bungee jumping. I purchased the transformer because it has a nice old plain coloured box and I wanted it for my vintage layout. Perhaps I should relegate it to being a prop with occasional use. Thanks everyone for their advice and warnings.

Mike

Your choice.

There are some strong views on the subject of old transformers, obviously, and in this thread loudly shouted. I keep waiting for factual information about actual problems that have occurred.

However, be assured that there are many train layouts running with these beautiful old transformers. Mine included.

I stand by my comments.

Good luck!

Bill

This debate raised a further valid point that has been made here which I should have addressed, and that is the legality of doing your own repairs.

Each country is different. New Zealand for example relaxed electrical regulations allowing some simple repairs to be undertaken by home handymen, whereas previously any electrical work was limited pretty much to being able to replace the 3-pin plug on a flex, and replacing a blown fuse in the switchboard and that was about it.

When they relaxed the regulations it was broadened so that homeowners could do some of their own domestic wiring etc, and there was the expected hue and cry from the electrical industry and unions warning of dire consequences, fatalities, and so on. The reality was that this did not happen, sure there have still been accidents, but there are no shortage of registered electricians and apprentices who have been injured or worse so having a qualification doesn't immunise you, it just improves the odds that any electrical work will be done in a professional manner.

Homeowners doing their own wiring are still required to have the work checked and certified before the actual connection, and they are not allowed to do any electrical work for another person for payment.

In NZ I held an Electrical Service Technician registration and this mainly covered Appliances which included Office Equipment (my requirement) and also white goods, and pretty much anything else where power is supplied by a flexible cord. It does not include 3-phase equipment and I am not authorised to work on fixed-wiring for payment. But having the certification meant I could also do the testing, certifying and repair of Transformers for the MMRC and this was very convenient for our "Goods for Sale" operation.

The point needs to be made that if your country prohibits any non-certified person from undertaking their own repairs to mains-powered equipment, and someone on this forum gave advise on how to do something which ultimately led to a death, well perhaps manslaughter charges might not quite arise but it would still be most regrettable for all concerned.

In my experience, most people who are not technically or electrically-minded will naturally shy away from attempting any sort of work where there may be a risk, and this is as it should be. We have fear and caution as a strong human condition for good cause. "Fools rush in" and all that.

SO - the assistance or advice given here while given in good faith, is also provided on the clear understanding that not only is the person using it confident in their abilities, but is also legally free to undertake this work in their own country.

Phew, hopefully that has covered things off better.

Edited by user 07 January 2012 23:52:55(UTC)  | Reason: Not specified

Thanks very much to all for taking the time to explain so thoroughly the likely causes of my transformer malfunctions as well as the perils of working on it myself. Even if I let sleeping dogs lie, as I likely will, I have some appreciation of how these devices function, which I find quite interesting. I did wire the basement in my house with the inspection of our hydro authority. If I do choose at some point to open up the old transformer I will take it to a qualified individual for their assessment.

Cheers,

Mike

Hi,

Does anyone know if the 6611 lighting transformer is ok, or if I buy one, should I take it apart and check?

Thanks

The 6611 was a model from the late 1970s/early 1980s and should be better than the 1960s and early 1970s models. As such, it might not deteriorate as much as one of the older models, but you also have to take into account that the construction may not quite be as long lasting as earlier models, meaning that it could age in other ways than what has been discussed for the older ones.

You can probably find a 6002 220V transformer at a good price by shopping around. There are a number on ebay.de

Regards

Mike C