"Yeah... Let's say "exotic" rather than odd ball?" Marion.
Presenting the 7036 gating heptode and the EC70/CV4507 subminiature triode.
The 7036 can be used for functions such as a sync pulse adder or gate. https://www.radiomuseum.org/tubes/tube_7036.html
The EC70 was designed as an oscillator for operation up to 600Mhz. Characteristics are similar to the 6J5. https://www.radiomuseum.org/tubes/tube_ec70.html
Till Eulenspiegel.
The line store unit will have to be solid state, there is no other easy solution to the problem other than an optical system. To date I've never had any luck with Dallas DS2010 FIFO chip. I've still got the application notes for this device and considering the chips were bought in 1988 so it's about time these were put to use. To keep things simple the 625 clock frequency will be 10Mhz and the 405 clock frequency 6.5Mhz. This will give 512 picture elements during the active 52 and 79microsecond video periods. The rather low clock frequencies will restrict the 625 video to 4mhz and 405 to about 2.7Mhz.
Till Eulenspiegel.
Moderator note - Updated post now merged with original.
Well, I guess those vintage chips might just qualify, though I was thinking 'thermionic all the way'. I guess at least if the conversion is thermionic, then solid state stores can be forgiven - plus of course, we no longer have the power stations in the UK to power it up!
Hi Marion, the line store will be hidden away from sight. If interpolation is to be considered we'll have to contrive a 64microsecond delay line.
Till Eulenspiegel.
Testing the TPG11. No HT shorts found so connect up the two units together and just plug it in to the mains and see what happens. No bangs or flashes. 'Scope connected to the various front panel monitor terminals and these show that there is a lot of activity going on. I reckon this instrument is a goer. The transformer in the mains frame sync lock transformer has been disconnected from the 6D2 diodes, refer to the circuit diagram on page three of this topic. Thankfully the windings check out OK. There is a fair bit ripple on the HT supply so the electrolytics in the PSU will need to be replaced.
RF present on the output socket.
Till Eulenspiegel.
Initial tests reveal that the master oscillator is running too fast. The correct frequency should be 20,250Hz, Even with adjustment of the oscillator control the lowest frequency attainable is 22,000Hz. The oscillator may need attention but I'm inclined to think the fault lies in the frame lock discriminator circuit. The master oscillator can be monitored from the front panel as can the control voltage from the discriminator to the master oscillator.
Till Eulenspiegel.
Has yours had the modification for flywheel sync, if you need it i have the 9 page document detailing this.
Found this relating to the oscillator too
Stephen
Hi Steven, any further information about this instrument would certainly be welcome. My info was sourced from Jonz Valvepage website.
Adjustment of P1 (R11) has brought the master oscillator to near correct frequency. Switched to 50Hz lock off shows a steady waveform on the 'scope but jitter is apparent when the 50hz lock is switched on. However, in the locked condition there is a flywheel sync condition and the frequency is maintained over a dwell of 15 to 20 degrees on the front panel frequency control R9.
Till Eulenspiegel.
I particularly like this exert from the 1951 BR&T test report
Summary of today's work on the TPG11.
Each divider has front panel fine adjustment control: 2250c/s, 250c/s and 50c/s. From the slider of the potentiometers is a 470Kohm resistor to the grid of the 6SN7GT triodes. The resistors were found to have gone high and have been replaced. With the master oscillator set to 20250c/s, or as close to that figure as possible the output waveform from the final divider has a repetition rate of 20mS.
However, the line sync generator isn't working properly so that stage is next to receive attention. The pulses from the twice line rate source are differentiated and used to trigger the line multivibrator, the negative going leading edge pulse is applied to the anode of section 2 of V13.
The attachment shows the rubbish line sync pulse.
Till Eulenspiegel.
Hi Steven, in the early 1950s the TPG11 must have been the most complex piece of test equipment ever to be used in workshops to repair domestic TV receivers.
Replaced V11 (6F13) in the half line sync pulse generator. Now have a near perfect waveform for the eight broad pulses in the sync pulse train.
Till Eulenspiegel.
Turned my attention to the divider chains. 50Hz lock switched off and the master oscillator set to 20250Hz, or thereabouts.
Adjust the first divide-by-nine circuit. Oscilloscope triggered by channel 1 and connected to the cathode of section 2 of V3.(6SN7)
Channel 2 is connected to the anode of V11. 2H pulses.
Adjust the divider so that nine 2H pulses are coincident with the duty cycle of the waveform in 'scope channel 1.
Till Eulenspiegel.
Good progress over the weekend.
Video waveforms at the anodes of the sync and video mixer valve V20.
This signal is sent direct to the monitor terminal "VID"+.
Sync height needs slight adjustment.
Till Eulenspiegel.
Have replaced all the TCC paper capacitors in the mains lock chassis. All had leaks in varying degrees. The 'scope traces show the eight frame sync broad pulses are coincident through the 50Hz AC zero crossing point
The mains lock discriminator circuit.
Till Eulenspiegel.
The RF modulator assembly is constructed to a very high standard. The modulator utilises the properties of the Mazda 6F33 pentode. This valve has special suppressor grid characteristics which permit the baseband video to be supplied to the third grid. To prevent the G3 going positive I believe a diode is connected inside the valve to G3.
The lower oscilloscope trace shows the modulated video signal. The sync tips do not go down to zero or almost zero carrier level.
Till Eulenspiegel.
