I lost the circuit diagram my TM-1000 some time ago and opened the case to try and figure out the circuitry and the diagram below is my best attempt. ...

The TM1000 antenna tuner has been round for many years, it is a very old design which has stood the test of time. It is not often that a really good piece of engineering comes along and does exactly what it says on the tin. The tin or chassis of this unit is a substantial piece of steel finished with a crackle paint job. All electrical parts are big and strong well up to the job. It will take 500 Watts all day long and easily handle 1000 Watts for short periods of time. It will also work very well as a QRP tuner as the internal losses are very low.

There are two versions one with and one without an internal balun. With the balun installed it is simply a matter of moving a jumper bar (link) to the output you need either balanced or unbalanced. The ferrite toroid transformer has a very substantial core with reasonably stout Enamelled Copper Wire (ECW) which looks to be about 1mm diameter.

The soldered joints are all very well made and should not fail under heavy operating conditions with wide temperature fluctuations. Any instrument which is constructed from metal will eventually tarnish and the bearings will eventually dry out. Where dissimilar metals come into contact there may be a small amount electrolysis this is not a problem at high power but will become apparent at very low power. On an old unit it is well worth checking that these connections are in good condition and a drop of oil on the bearings.

Do not be fooled into thinking that this is a simple piece of equipment the schematic circuit diagram would lead you to believe. Mechanically it is a work of sheer genius and must have taken years to develop. Circuits like this have been round since Marconi’s time and the mechanics have evolved over this time. This is not a piece of junk it is the Rolls Royce or Quad of the species. If you can pick one up grab it at any price and get to work.

The balun board is simplicity itself, switching between balanced and unbalanced is by moving the position of the jumper bar see # 01. Dust is another curse a soft brush is the best way to remove it from between the capacitor plates. The remainder can be removed with a vacuum cleaner. Hopefully anyone finding this blog will get in contact and swap ideas and perfect the circuit where it is not correct.

I had a search on the internet and I found this US Patent which looks exactly like the TM1000 circuit schematic.
I have re-drawn it using the UK parts I understand, the only difference is that the twin gang tuning capacitor is not split by the rollercoaster inductor, only the lower half of the tune capacitor goes to earth.
Note the Nevada TM1000 predates this US patent by several decades.

Data de publicação   29 maio 2007   The patent reads:- Resumo In a T network tuner, a variable shunt capacitor is provided between the signal input and ground that is ganged to the variable input matching capacitor. The operation is mechanically arranged such that, as one decreases the capacitance of the variable input matching capacitor, one increases the capacitance of the shunt capacitor to assist in high frequency matching, both to increase the maximum matchable load resistance and to decrease the minimum matchable load resistance. The variable shunt capacitor therefore assists at the high frequency ranges to bring the antenna impedances down to the transmitter output impedance, thus to establish an extended matching range tuner capable working between 160 and 10 meters.

We still have the potential for circulating RF on the earthy side of the inductor.

On 29/04/2018 18:40, Antony Nailer G4 CFY wrote:
Dear Adrian.
The solution to the rotary inductor is on course a coil with a number of taps. You don't really need infinite increments as the capacitors make up the incremental bit. All you need is lots of taps on your old inductor and a rotary switch. The taps need to be at half, quarter, eighth, and sixteenth turns. That overcomes the problem of bad connections through the bearings.
Regards,
Tony



Hi Tony, Many thanks for the good information regarding tapping the coil at various increments using a ceramic Yaxley switch. If I can get hold of one of these switches I haven't seen one of these excellent switches since I retired from X-Ray Engineering.





All I need is one wafer the rest are redundant but can remain resident within the TM1000 as spares. The ideal way to connect the tappings to the switch would be to use the silver ink pipes from a redundant Mingograph EEG recorder. ..... but I'll make do with copper wire. Yours is a good solution as it removes the problem of squeaking verners and dry rotary connections.
I have redraw a section of the circuit to show the implementation of a Yaxley switch. The incriments can be evenly spaced depending upon how many contacts are on the switch. The switch and silver pipes are of the period..1960's... only the best will do. Have I your permission to publish your e-mail below, Please. Kindest Regards
Adrian
The printed circuit board has now been made more obvious. We may be getting closer to the original circuirt schematic which would be a good thing as this machine can tune a barn door.