The screen aperture has a 30 degree chamfer around the edges. That part of the job went well. However, things didn't go well when it came to routing out the 5mm recess for the implosion glass. The router tool kinda went wild and ruined the panel. So that panel will join the woodworm damaged parts. Scrap!
Looks good, a lot of skill and hard work to get to this point, onwards they said, what’s next veneer?
Frank
That is coming along nicely! Shame about the new top panel going wrong. One day I'll have a go at repairing the water damaged cabinet on my Stella ST2049a, looks like it'd be dead easy compared to the Baird!
Regards,
Lloyd
It will be possible to repair the damaged CRT display panel but instead I will make a new one which will be constructed from two pieces of 6mm plywood glued together.
I'm now on the lookout for veneer for the front panels.
Till Eulenspiegel.
The cabinet reconstruction is progressing very well. The control panel is the last cabinet part to be made. I'll attempt to do this later this week. In the meantime let's take a look at the vision receiver. Signals are supplied direct to the mixer, no RF amplifier. This was a common practise in early TV receivers. Because the intermediate frequency is low the four stage amplifier should provide excellent gain.
The Mullard TSP4 pentodes have a gm of 4.2ma/V which is a good figure for early television RF pentodes. Because the set employs a large CRT a full wave demodulator is employed in order to avoid a fine dot pattern appearing on the screen. A Mullard 2D4A double-diode is used as the vision detector. A TSP4 is used as the video amplifier.
Positive going video is supplied to the CRT grid via a capacitor. No DC restoration. The later T23 has a DC restorer diode in the EHT supply unit. The brightness control setting provides the sync tip reference.
Till Eulenspiegel.
The control panel is the last cabinet part to be made and it is proving to be a bit difficult to replicate but I will have something show on the forum by the weekend.
The vision receiver and the power supply units are on the bench for servicing. We'll soon find out the intermediate frequency and the passband characteristics of the IF amplifier.
Testing the power supply unit. The 16mfd reservoir capacitor and the 24mfd main smoothing capacitor were found to be useless so for the time being two 8 + 8 mfd capacitors will be used until the correct components can be found.
Under no load and with only 150VAC supplied from the variac the smoothed HT voltage is 300V. Later today the vision and sound receivers will be connected to the power supply.
Till Eulenspiegel.
Today's report is about the good progress I'm making with the sound and vision receiver units. The oscilloscope trace shows the negative going video present at the grid of the TSP4 video output valve. Despite having no RF amplifier the vision receiver has high gain. It has been established that the vision IF amplifier is aligned to the upper sideband which means there is a deep "trough" between the vision and sound passbands. The vision IF is 13mc/s, much higher than I thought it would have been.
Much more work needs to be done on the vision receiver but the results so far are very encouraging.
The 13Mc/s vision IF came as a surprise because as the demodulator is of the full wave type I was expecting an IF in the order of 4 to 8mc/s.
Till Eulenspiegel.
Today the new control panel was test fitted.
The panel is canted back 35 degrees which made it necessary to adjust the angle of the cutting disc on that scary saw bench.
Till Eulenspiegel.
The restoration of the Baird T5 is progressing well. Just two more jobs to do before the wood veneers are applied to the surfaces of the cabinet front panel, the control panel and the CRT screen panel.
First task to do this weekend is make the specially shaped beading fitted between the control panel and the upper panel, see the attached pictures. It might be possible to use ordinary stock beading available from B & Q. Again, the saw bench will cut out the 30 degree chamfer.
The second task is to make the cut out in the front panel for the door to access the timebase controls.
Till Eulenspiegel.
Will you need a new door for the time base controls, it looks like the woodworm have got that piece of wood?
I am not posting much but enjoying the journey.
Frank
Hi Frank, it might be a good idea to make a new door although the original is quite sold. Easy enough part to replicate.
Till Eulenspiegel.
Time to apply wood dye on the side panels, but before any attempt to do this I'll test the various dyes and polishes on wood off-cuts. The attached picture shows that the finish needs to darkened in order to resemble the wood surfaces of the original panels.
Till Eulenspiegel.
The grain should look good with the staining.
Frank
Hi Frank,
After several applications of wood dye on the test piece I'm sure the side panels can be stained and polished.
But the wood dye should be applied outdoors and not in the workshop, nasty fumes given off during the application process.
Till Eulenspiegel.
Hi David.
I remember when you were up here some years ago you were under the influence of the fumes from French polish, it was quite funny in retrospect.
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
Hi Trevor, you've got to be careful applying the wood stain, it also gives off unhealthy fumes so for my well being's sake the panels were taken outdoors.
The attached picture shows that the panel requires more wood dye applied before the dark finish is achieved.
Till Eulenspiegel.
Hi David.
The grain on that wood looks like the BBC weather map with a massive anti cyclone over Scotland...... I wish!!
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
