Dynatron TV32

[high_vacuum_house]

Also as a peculiar coincidence, the set was picked up from Pearsons storage yard!! Would be ironic if it was run by the same family!

[high_vacuum_house]

There is good news for the TV32 restoration.

I found that the concentric volume on/off and brightness pot was broken. The centre spindle just spun around inside seemingly not connected to much. I found a replacement one which was replaced. An IEC lead on a dangly bit of wire cobbled in behind the mains Belling mains socket was removed and the missing screws and nuts for this were found and fitted.

After cleaning the top of the chassis, cleaning all of the valveholders and checking all was well underneath, I powered it up slowly with the variac whilst monitoring the HT. The VHF radio worked, There is a bulb that lights when the 13 channel tuner is switched to one of the three radio positions. The heaters to the timebases and CRT are switched off also.

Bringing it up on a television channel brought a nice sweet sounding EHT whistle with quite a low mains voltage and measuring EHT eventually got 19KV DC from the anode cap. The LOPT was already dried out and the area cleaned from dust.

Next is to reinstall the chassis back in the Meccano angle iron frame properly (several screws were missing) with the CRT and connect up the CRT anode and see if I can get something on the screen. Then to look at replacing the various wax capacitors around the chassis which for once look fairly healthy and not sticky!

Pictures of the chassis being tested. The purple glow on the left in the dark is the EHT cavity connector fizzing with corona discharge as it has sharp points!

Christopher Capener

[high_vacuum_house]

I managed to get the chassis back into the frame and screwed down this evening, Not easy due to the weight of the chassis.

With everything connected back up, I wanted to get "first light" before replacing wax capacitors. I ran it up on the variac and got a nice quite bright raster that is a bit squashed vertically. Connecting up the Hedghog converter and fiddling with the line, frame contrast and brightness controls, I get very off test card!! Not bad as none of the waxies in the set have been changed yet! The test tone comes through fairly clear as well.

Christopher Capener

[Colourstar]

Well done Christopher- What a set! That chassis is a truly thing of beauty!

Incidentally, as a Nottingham lad, I remember Pearsons very well indeed. It was a really splendid department store. Their lift had a uniformed attendant, who used to let me press the illuminated buttons as a special treat on the rare occasions when I went there with my mum or dad. I suppose that must have been in the 1970s.

Steve

[Laurence Smith]

Excellent. Looks like the CRT has plenty of emission left in it too.

[high_vacuum_house]

I have been slowly working on the chassis carefully replacing capacitors in the frame timebase and sync separator. This has tamed the raster and is considerably more stable and controllable. All of the wax paper capacitors (Plastiseal?) have been pretty poor with a couple being near 50K resistors than capacitors.

Last night I replaced several capacitors in the AGC circuit which has improved the operation of the tuner, although I have an odd problem which I haven't come across before.
The picture below shows the picture when tuned in.
The contrast is obviously too low at this point. If I increase the contrast from this point even slightly more, the contrast increases (giving a correct picture for half a second or so) the line and frame scans balloon outwards and the picture is lost completely either with a grey raster or blanks out the raster altogether. Reducing the contrast control back and then advancing it will cause the same effect.

Also the timebase sync is lost when the picture balloons out and fades away.

I am thinking there may still be an issue in the AGC circuit or the surrounding area, Or another possibility could be the original EY86 rectifier running out of steam if there was an increased beam current with higher contrast present. There are still a couple of waxies in the line timebase to tackle as well but was working through the various sections of the chassis methodically.

Many thanks,
Christopher Capener

[high_vacuum_house]

The EHT rectifier was replaced this evening after a struggle.

The first NOS Mullard EY86 was cracked
The second NOS Mullard one glowed purple and not a dot was seen on the CRT
Third NOS Mullard EY86 turned out to be a DY86 instead (who at Mullard wrapped that one up as it hadn't been disturbed in the original wrapping paper!) although it didn't matter as this was cracked as well!

Sometimes boxes of NOS telly valves are not all what they were cracked up to be (pun intended!)

So I found a NOS Brimar EY86 which was duly fitted and although has a slight purple glow at zero beam current works much better than the rectifier which was in there. This was a Pinnacle branded KY80.

The brightness and contrast controls are still very critical and seem to adjust each other, but at least the video is better. The width is too great, although there are still several wax capacitors to be replaced in the line timebase circuit. This I will tackle next.

Christopher Capener

[high_vacuum_house]

Good evening,
Good progress has been made on the TV32 this week.

With the EHT overwind baking gently with 6mA current flowing through it for approx. 6 watts dissipation. Nice and warm to the touch. This was set up and left for 5 days.

Whilst this was left alone, the Garrard 4SP record player was serviced. The speed controller was seized and the whole mechanism stiff from old grease. The mechanisms were stripped down and degreased and carefully lubricated with either fine clock oil or fine instrument grease. The motor was also stripped and relubricated.

The whole lot looked a lot better and went back together easily enough. The rubber idler tyre is in good condition and is nice and supple.

The only components to have deteriorated here were the main record player suspension rubbers. These had crumbled and caused the player mechanism to sink. This caused the rim of the turntable to come into contact with the motor board. New grommets have been ordered to replace these.

Back to the chassis, the sound output stage 32uF HT decoupling capacitor was getting warm and was replaced. The original capacitor was poking through the chassis and was left disconnected and a replacement routed alongside using a spare unused tag.

With the final couple of wax capacitors replaced, testing has been in progress today and the chassis ran for nearly 5 hours without any deterioration in vision or sound quality.

The cabinet has been moved indoors (whilst wife was away!) and the record player lid has been removed. This is the only item that needs some tidying up work. This will make refitting the chassis much easier as not only is it damm heavy, but a tight fit in the cabinet! The cabinet remainder just needs a good clean and polish.

The board which fits behind the controls had the decals unscrewed and polished up. The decals were cleaned. There is a bracket for a lamp which lights up the radio stations on the channel selector when the set is tuned to the Home Light or Third VHF radio channels. This also disconnects the HT and heater supplies to the timebases and CRT, Hence the lamp to show that the set is switched on. This had become detached and was glued back on.

Christopher Capener

[high_vacuum_house]

Good evening,
More progress today on the Dynatron. The front control panel was reassembled and glued back onto its mounting blocks which had come unstuck over time.

I managed to find an exact date whilst cleaning up and refitting the aluminium bowler hat (Tube base protector) to the CRT framework. 19 November 1957 A nice find!

The chassis went in easier than when it came out. The record player motor board and top lid were not fitted, so that made lifting and manhandling the chassis much easier with access through the top.

The record player motor board is steel and covered with a felt material. This was pretty filthy, possibly a sticky drink got spilt on it years ago, and under the record platter there were signs that some of the grease from the mechanism had crept over the years. This has now been cleaned with foaming carpet cleaner and looks much better, and is currently drying.
I am waiting for the grommets for the suspension to arrive to mount the record player mechanism to it before it can be fitted back to the cabinet.

Finally, this set is pictured next to an Ekco TCG316 which is a similar tele-gram console set with a smaller CRT and built in 3 channel VHF radio. This set is not in the best condition, but hopefully restorable.

Christopher Capener

[TonyDuell]

Originally Posted by high_vacuum_house

With the EHT overwind baking gently with 6mA current flowing through it for approx. 6 watts dissipation. Nice and warm to the touch. This was set up and left for 5 days.

Those figures imply your overwind has a resistance of about 160k Ohms and you've connected 1kV across it. Neither of which I believe.

[Colourstar]

Crikey, the Dynatron is a beast! It positively dwarfs the Ekco TCG316. Well done on your restoration work so far, it's a lovely set and still exudes an air of quality all these years later.

Steve

[high_vacuum_house]

The EHT overwind has a resistance of around 15K which surprised me why there was little current flowing when I set up my bench power supply.

With the rubber grommets delivered, I was able to reassemble the record player mechanism onto the motor board and refit it to the top of the cabinet. The lid was then refitted along with the spring operated lid stay which had some grease to its pivots as it made boinging noises when the lid was raised!

It uses a car aerial plug and socket for the crystal pick up and a 2 pin American mains plug and socket for the mains supply to the motor.

With all reassembled, The record player worked faultlessly first time, A bit sluggish for a minute or 2 until it settled down.

First record played was Dvorak's new world symphony, Makes me think of the "television comes to London" film every time I hear it! The sound quality is pretty good considering the push pull output stage.

You can see the lamp lighting up the radio channels behind the turret tuner controls as when any of these 3 channels are selected the CRT and timebases do not operate. There is a further switch on the front to select either Gram or TV/VHF next to the tone control. The Ekco TCG316 does not have a tone control.

Christopher Capener

[dave walsh]

That's all a very long way from post 40 Christopher but it looks [and evidently sounds] great! It is surprising how heavy some of this vintage gear can be. Having watched you shift the B28 from Rammy, though, you are certainly the man for the job. I disassembled a wall of Radios from there recently only to discover that they had suddenly become much heavier and higher up than before after 20 years-or is it just me I liked the way that you linked in the TV32 with a Dvorak vinyl, on the first go with the record deck. I suppose that the weight does help a lot with the audio output? If you do send an article to the Bulletin I'm sure it will go down very well.

Dave W
Bexhill [at present]