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1963 Ever-Ready experimental all-transistor TV set.  

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PYE625
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An especially interesting set indeed. The CRT screen seems very square faced and flat, an early "FST" perhaps.

To understand the black art of electronics is to understand witchcraft.
Andrew.

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Posted : 19/03/2020 6:49 pm
jjl
 jjl
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Posted by: @till

Four 5000uF parallel connected capacitors are used to ensure the supply voltage to the scanning PCB is dead smooth.

ER TV 4X5000uF

Those are the largest value capacitors I've seen in equipment of this age. I imagine that this television would have cost an absolute fortune to make and would never have been viable as a commercial product.

 

John

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Posted : 21/03/2020 10:29 am
Nuvistor
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Presume the capacitors were specials unless they were in the computers around that time.

 

Frank

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Posted : 21/03/2020 11:18 am
Till Eulenspiegel
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The Pye TT1 all-transistor TV set of 1960/61 employed two 10,000microfarad capacitors to ensure that the 10 volt supply line was dead smooth. Such high value capacitors were well known and used in industrial and computer equipment.

I'm presently tracing out the circuit of the frame timebase and will post up my interpretation of circuits later today. The oscillator is of the blocking type, that has been confirmed. Two Lucas diodes are employed, one as a over-swing damper across the transformer collector winding. The other diode is an isolation diode between the collector of the 2G302 oscillator transistor and the sawtooth forming capacitor. You'll see something similar in the all-transistor BRC 1590 chassis which was introduced ten years after the Ever-Ready set was made. A 2G302 transistor is employed as a frame sync pulse clipper, another 2G302 is employed as the buffer between the sync separator which again is a 2G302.

The line output stage is of the type invented in the 1930s by A.D.Blumlein. The 2N1046 functions as a switch and the sawtooth waveform is generated in the high inductance scanning coils. The OA5 diode is the flyback damper.

The positions of the line and frame hold controls has been found.

Till Eulenspiegel.

Mod Note: Fixed post formatting 👍 

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Posted : 21/03/2020 4:23 pm
Jac Janssen
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@till

What an amazing set David!
I'm looking forward to see how it performs.

Jac

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Posted : 21/03/2020 7:37 pm
Till Eulenspiegel
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Hello Jac,  I'm sure this will turn out to be a truly excellent receiver. But before that happens every stage of the circuit will have to be traced out and documented. Tomorrow, I might be in a position to test the timebase panel in isolation from the main chassis. The attachment shows a rather rough and ready circuit diagram of the frame timebase.

ER TV FTB cct

 Till Eulenspiegel.

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Posted : 21/03/2020 11:04 pm
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Till Eulenspiegel
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The Ever-Ready experimental transistor TV set was developed with participation of the Thorn laboratories. Compare the circuit of the frame timebase circuit of the 1961 Ferguson 743T with the FTB of the ER set.

ER TV 743 FTB

The timebase repetition rate is determined by C117 and R134, R134 and R135. Note the isolation diode W7, also the damper diode W6. The sawtooth forming capacitors are C121 and C122. 

Till Eulenspiegel.

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Posted : 22/03/2020 12:12 pm
Till Eulenspiegel
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Those 2G302 transistors close to the line output transistor are used in the frame and line sync blanking circuit. Ref. to previous post.

ER TV BLKG detail

 Having established what the transistors do I'll move on to tracing out the sync separator stage. 

Till Eulenspiegel.

 

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Posted : 22/03/2020 3:16 pm
Till Eulenspiegel
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The sync separator stage.

ER TV Sync Sep

 It can be seen that the sync separator transistor is in a conductive state and will be turned off when positive going sync pulses are applied to the base.

Till Eulenspiegel.

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Posted : 23/03/2020 10:06 am
Till Eulenspiegel
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Attention is now turned to the line oscillator and the indirect sync system.

The line oscillator has three windings. Two are the collector and base windings in the blocking oscillator, the third winding is the base drive for the 2N1046 line output transistor.

The method of controlling the frequency and phase of the oscillator quite different to anything I've ever seen in a domestic television set.

 A 2G302 transistor accepts the differentiated sync pulses and conducts on the negative going leading edge. The transistor shares the same 22Kohm collector load resistor with another 2G302 transistor. This transistor accepts the flyback pulse from the line output transistor. It's here where the strangeness begins. Common logic would suggest the that voltages on the common load resistor will provide the control of the line oscillator. Not so, instead the controlling voltage is derived from the 15K emitter load resistor. In series with the base winding of the line oscillator transformer is an adjustable inductor, this is obviously a key component is the flywheel sync system, if one can call it that.

Later today I will submit my interpretation of the line oscillator and sync circuits. A diagram and more suggestions on how the circuit works.

Till Eulenspiegel.

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Posted : 25/03/2020 1:16 pm
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Till Eulenspiegel
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The line and frame blanking mixer circuit.

ER TV BLKG

 

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Posted : 25/03/2020 2:46 pm
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Till Eulenspiegel
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The circuit of the line sync system.  I reckon it's a comparator. The transistor which receives it's drive from the line output transistor is effectively shunted across the sync amplifier transistor. The control voltage is developed across the 15Kohm emitter resistor.   The adjustable inductor is possibly the phasing coil. Adjust to centralise the picture.

ER TV Line Sync

 Till Eulenspiegel.

 

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Posted : 25/03/2020 6:21 pm
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Till Eulenspiegel
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Testing the timebase  panel.

Power supplier was set for 8volts and connected across the 5000uF capacitors.

20mS sawtooth waveform at the collector of the OC200 frame output transistor.

ER TV FTB wfm2

The waveform across the sawtooth forming capacitor in the line blocking oscillator.

ER TV Line Sync wfm1

 The line timebase is running too slow.

 Waveforms are present at the base and collector of the 2N1046 line output transistor.  

Till Eulenspiegel.

 

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Posted : 26/03/2020 12:25 pm
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Nuvistor
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How slow, is it waiting for sync?

 

Frank

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Posted : 26/03/2020 12:53 pm
Till Eulenspiegel
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Posted by: @nuvistor

How slow, is it waiting for sync?

Hi Frank, that may well be the matter.  The line sync discriminator is not the usual balanced type and may well need the presence of sync pulses to bring it up to the correct operating frequency.  According to the oscilloscope the repetition rate is 443Hz.  As the EHT is generated by separate circuits the free running line timebase frequency is not important.

Till Eulenspiegel.

 

Mod Note: Fixed post formatting 👍 

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Posted : 26/03/2020 1:25 pm
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