Hi Walters,

The transformer is a variac, with a slider running across the secondary windings when you turn the knob. Looks like that part of the windings where the problem occurs are either dirty or roasted/oxidized. To solve it you´ll have to take the housing off and clean the windings and the slider. Alternatively you can try to just take off the red knob, if you can see the slider through the opening of the casing use some contact cleaning spray, turn the knob several times and hope for the best.

Robert

Hi Chas,
Had a quick look at my 6647, which is probably the same except for the primary voltage. You will have to take it apart, on the left and right side top half you´ll find 4 small plastic plugs. It looks like they hold the two halves together. How to get them out I don´t know, I would try to drill them out carefully. I don´t have access to any further information as to how the transformer is constructed but judging from the outside I think that once you have removed the top half, the knob will come off with it, freeing up the actual slider mechanism. I pretty sure it is the old type of slider mechanism, when turning the knob you can feel the contact scraping across the wires of the secondary coil. To put it back together again you´ll have to replace the plastic plugs with fitting self-tapping screws taking care that they are of the right lenght so that only the casing is held together without them touching any metal parts inside. Hope this helps you to get it going again,

Robert

I still have yet to try this with my spare tranfo as we discussed in the old thread. Once you got the cover off, were you able to see if there was an easier way to get it opened? To me, it looks like it's a one-way assembly, I don't' think there is any way to open it once it's put together...so a cutting method as you suggest is required. It looks to me like there are four "posts" that hold the cover on, I was thinking about carefully drilling out the holes where the posts connect to the top cover to remove it. Based on your experience what do you think?

-Brandon

"Houston, we have a problem!"

I went to start up the transformer the other morning at it was dead!

I took the unit apart and the copper wire I used broke at the solder joint from too much flexing. It just fell off. The tech in the back had some multi-strand stainless steel wire that he soldered in and the train was back up and running.

I should have known that the copper was going to fail sooner or later. Eventually, I'll find another piece of solid core stainless (like the original) and solder that back into the transformer.