Bush TUG26.

[FERNSEH]

Presenting the Bush TUG26. Electrically, this set contains certain circuit features as found in late production models TV22A and TV24A/C. Also in some respects the 14" TV32 is a development of the TUG26, the switched width control for example.
The set has been in the workshop for many years so it's about time it received some attention. We are convinced the 16" metal cone CRT is a dud, but the first stage of the repair will be to return the chassis to a working condition, then the state of the CRT can be determined. If the tube faulty we must accept the fact any chance finding a good bright MW41-1 or EE T901A is remote. The American near equivalent is the 16GP4A but what's chances of finding on of those?
A long time ago there an article in the Practical Television magazine about substituting the round faceplate MW41-1 with an MW43-64/9 rectangular CRT.
Instructions were given on how to make a wooden cradle to mount the front of the tube. Now this something we can consider for the TUG26, instead of wooden supports hooks, springs and webbing could be considered.
There is a spare MW43-69 in the shop.

DFWB.

[bobhowe]

Hi David could you wake the tube up slowly & give it a little Tickle & if no good use the MW43-69 but this restoration must involve your famous ADAPTER PLATE regards Bob

[high_vacuum_house]

Good evening,
I presume the common failure of the metal cone CRT's would be the slow outgassing of the metal cone itself along with rather large glass to metal seals slowly leaking.

Christopher Capener

p.s I presume a lot less messy or hazardous should you accidently drop it !!

[FERNSEH]

Hi Bob,
We're convinced there is some life in the round tube. To fit the bigger tube there'll be all sorts of adaptor blocks, plates and straps. It's never been done to this model. A lot of Ferguson sets were modified in this manner.

DFWB.

[bobhowe]

Yes I'm sure you will have this one working regards Bob

[FERNSEH]

Showing the chassis of the TUG26. Note the similar appearance as the TV22A. Uses the then newly introduced PL83 pentode in the video and audio output stages. Much of the rubber insulation wiring is perished, been a few flashes and bangs. There's going to be a lot of work done to this chassis to return it to working order.

DFWB.

[FERNSEH]

The chassis is now on the bench. As can be seen in the attached picture there is plenty evidence the set has received attention in the not so distant past. Well, it was the spring of 2011 if you consider that not long ago.

DFWB.

[FERNSEH]

The attachment shows the possible cause of those pyrotechnics six years ago.
A rubber insulated lead between the brightness control and the control grid of the CRT was found to be perished and was coming into contact with the top of the heater chain. Those familiar with the TV22 will have on occasions met similar wiring problems.

DFWB..

[FERNSEH]

More perished wiring replaced today. The red and green mains voltage adjusting leads were in a bad state and have been replaced. Also some wiring in the heater chain. The chassis is at present still on the bench for it's initial tests. The heater chain thermistor was found to be faulty, you do expect this component to have a high resistance when cold but this one was reading 140Kohms. Also the resistor in parallel with it was O.C. indicating that it has been overloaded. The replacement thermistor is a Mullard VA1026, this components reads 1.2Kohms when cold, no parallel resistor required.
First tests: Pins 1 and 12 of the CRT base connector shorted out for heater chain continuity. Chassis connected to the variac and the voltage brought up in stages to give the electrolytic capacitors a chance to recover after their long slumber. Finally, after the full mains voltage is supplied there is present at the anode of the EY51 a healthy spark and it seems the two EHT Visconols are OK because there a nice big spark present there as well. CRT base voltages are: G1 0 to 112 volts depending on the setting of the brightness control. CRT cathode is 120 volts and the first anode volts are 313volts. Don't forget the scan coils are not connected so the line timebase will not be working a full efficiency. The frame timebase is also working and oscilloscope waveforms present at the secondary of the output transformer prove that the oscillator is operating at 20mS.
This chassis is ready to reinstalled into the cabinet.

DFWB.

[FERNSEH]

Today the chassis was installed in the cabinet, the link between tags 1 and 12 on the CRT socket removed. We're going to find out if the MW41-1 is any good.
Well, I think it is safe to say that the CRT is useless. The EHT is 12KV, the CRT base voltages are: first anode 300volts, cathode 121V and the grid 110V. The ion trap magnet was lined up with pin 3 and moved about this position. Next, the magnet rotated 180 degrees just in case it had been fitted the other way around.
If the CRT had any emission there would be a raster. Also, the heater voltage measured at pins 1 and 12 read only 3.2 volts which tells us the tube has a partially shorted heater.
To sum up, the tube is without doubt useless and the only alternative is to install the all glass MW43-69. But I don't think anyone has ever done this tube substitution in the TUG26?

DFWB.

[Nuvistor]

This is going to become more of a problem, good valves are relatively easy to find, not so good CRT's.
Must be frustrating after putting all that work in to the set.
Frank

[FERNSEH]

Hi Frank,
that's right at the present time valves are not the problem but with CRTs that's a different matter. I took a chance with the Sobell T143 and the gamble paid off, the CRT is excellent. The truth is after servicing the chassis of the Bush I wasn't expecting any results from the MW41-1 CRT. However, I do have a spare MW43-69 and I'm sure it can be installed in the TUG26 by some means or other. No electrical modifications required except for removing the two TCC Visconol capacitors, these are not required because the CRT aquadag coating will serve as the EHT smoothing capacitor.

DFWB.

[FERNSEH]

At last there is illumination on the screen. The ion trap magnet has been replaced with the type with an arrow embossed on the metal tag so we'll know the correct position and direction the magnet should be set to. The grid and cathode pins of the CRT shorted circuited together so the tube operates at zero bias. After an hour a faint glimmer could be seen on the screen, adjustment of the ion trap improved matters. I still don't there is any useful life left in the CRT but there will be no harm leaving the set switched on over a long period of time.

DFWB.

[simpsons]

Hi DFWB, I have been reading with interest your work on the Bush TUG26 which only recently I was also involved in renovating.

Luckily the CRT was in excellent condition and it was quite something to see a flat screen picture on a 70 year old set!! Test card C looked almost photographic!!

The later rectangular tubes, which of course were convex, didn't have quite the same impact but then they didn't have 12KV on a metal cone waiting to be touched by a serviceman's hand. Not being sexist but I cannot remember a single female service technician when I was in the field but happy to be corrected.

Let's hope that the CRT warms up for although there were more metal coned sets in the USA I don't suppose getting one shipped over here, should you find one, would be easy.

As an aside, this was the first TV my dad bought just to see the Coronation. Living in Mitcham Surrey, you could could pick up Alexander Palace on a shoe string. On the day, the invited guests and neighbours all sat in front of the 16" screen and with much fanfare the set was switched on.

I was only about 6 and so much of the following is historic but anyway, we waited and waited, the sound came on but no picture and so it remained for the rest of the event. I don't know what went wrong but it must have taken the shine off the day and buying a TV. But hey ho it was soon working and I enjoyed many programs including Quatermass and the Pit which was watched more in fear much like the early Doctor Who. I dare not mention Watch with Mother which brings back fond memories as that would be too telling on how much of a softy I was.

I am so glad that my Children watched Blue Peter rather than Grange Hill due in no small part to the number of different TV's brought home for a soak test, which only I was allowed to touch, but I digress.

Let's hope the TUG's CRT wakes up and that you too can see the delight of a flat screen TV. Who knows, one day all TV's will be like that!!

Help Call the Doctor!!

Keep up the good work.

Chris nee Simpsons

[FERNSEH]

Hi Chris,
Not good news this morning, the raster has become much dimmer, the tube is scrap. With regards to the similar 16" metal cone CRTs made in the USA, the once common 16GP4A is almost a direct equivalent to the MW41-1, the only difference is the heater current which is 0.6amp.
However, I think TV collectors and restorers in the States are having the same problems with these old metal cone CRTs.

DFWB.

[Mikey405]

It's a shame about that tube David. The set itself looks very nice and quite striking with that flat CRT. I have two sets that use the same tube - an English Electric table set (16T11 or something like that) which has a watchable tube (if not over bright) and an enormous Invicta radiogram with the equivalent of a Pye FV2 chassis in it. I have no idea what the Invicta tube is like though.

I hope you have a bit of luck with your tube David. Is it boostable? You've probably got nothing to lose...

[simpsons]

For what it is worth, The Early Television Museum across the pond have a 16GP4 showing good emission for sale. Contact them thru info@earlytelevision.org for further details.

Provided that they can box it for shipping, the cost of doing so by sea freight may be viable.

Chris nee Simpsons

[FERNSEH]

Hi Mike,
That's right we have nothing to loose by giving the CRT a tickle with the reactivator. I reckon that the dim raster is a result of the CR tube gun having that partially shorted heater, at present only 3.2 volts can be measured at pins 1 and 12.
Sure enough a ordinary 17" CRT can be installed but it's most likely the mask will have to be replaced to accommodate the spherical faceplate. The set would just become an ordinary 17" and what this set is all about is that unique screen presentation.
Hi Chris,
That's a good suggestion, contact the ETF, a 16GP4 is listed.
http://www.earlytelevision.org/crts_for_sale_b-w.html

DFWB.

[FERNSEH]

In 1953 Philips introduced a new metal cone CRT, the rectangular faceplate type MW43-43. In the UK the tube was marketed by Mullard. It was most likely used by several Continental TV manufactures and in the UK by Ferguson and Ferranti. Can't think of any others. The tube was out of favour by 1955.
Returning to the TUG26. Here's an idea, why not consider the MW36-24/44 as a replacement for the almost impossible to find MW41-1? After all the actual screen area is not much less than the 16" tube and it also has an almost flat faceplate. Same power requirements and deflection angle.

DFWB.