15-02-2014, 10:38 PM (This post was last modified: 15-02-2014, 10:42 PM by Refugee.)
The inverter I had a look at some time ago looks like it dates from 1967 from the date codes on the transistors and has some degree of regulation provided by the negative HT connection being made via the biasing circuit for the transistors. The unmarked resistor is 3.6 ohms. The writing looks a bit rough on the 150 ohm resistor too.
It is a very rough reverse engineering diagram I am afraid. All the windings are on a single core but it is not clear in the diagram.
The secondary of the transformer is sadly open circuit and I did an experiment to see if all the lams can be extracted from the transformer and got all but one or two out intact.
The transformer winder needs the top bearing finished off and then I will fix the transformer and start a new thread.
PNP germaniums, got to get my head around the upside-downness of it! I guess a transformer would work backwards. Just a slight concern as to the current taken - maybe a more robust transformer than the one I used would be needed. It'll make an interesting thread, one I'll watch out for.
Tony
I elected to draw it that way to show how the regulation works. The negative HT output goes through the biasing resistor for the two transistors and it smoothed at the center tap with a 50uf capacitor base to negative.
It is difficult to work out if it is a currant limiter or a voltage regulator.
It is clear that there are 4 windings and to get to the fault 3 will have to come off the bobbin.
The collector windings are wound over and under the secondary push pull audio style and lead out as two pairs to be linked on the tag strip. The transformer has been wound for the job so it is not just a backwards mains part.
The 6.3V heaters go across the battery directly.
Then you'll need to know the turns ratio of each winding to the whole, presumably both collectors have the same winding size. Will this make for a more complex winding job, and is your winder going to handle it, as its probably not worth having the thing rewound by a specialist. Assuming it can, it has the makings of an unusual rebuild/restoration.
Tony
Well the transformer winder is an almost complete ice cream maker conversion with a turns counter and an electronic auto stop on a preset count.
It unlike commercial units has a vertical chuck. The upper bearing is yet to be finished as are is the bobbin mounting parts. The counter works and does generate the stop signal as does the bobbin drive from below the deck.
The photo of the transformer coil and lams was taken on the deck of the winder with the feed bobbins visible.
The first job after what is on the bench now is a scope that needs the PDA rewound so it is looking good to get the winder finished off soon.
I will do a proper thread for the winder as I have all the photos including doing the counter and auto stop parts.