White Ibbotson Worries - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

Radio Wrangler · 22nd Dec 2015, 9:55 am

I think the cabinet designer must have been the same guy who did the "Stevenson Shield"

Though the projection lens porthole gives it the appearance of Captain Nemo's TV set.

David

Duke_Nukem · 22nd Dec 2015, 10:45 am

Just occured to me, what did you use to clean the optics ?

TTFN,
Jon

julie_m · 22nd Dec 2015, 9:18 pm

That test card looks superb!

What's the sound like? It appears to have a decent-sized speaker.

I can imagine such a set in use in a gentlemen's drinking establishment ...

Mikey405 · 22nd Dec 2015, 10:07 pm

Quote:

Originally Posted by Hunts smoothing bomb

I never thought the images produced by these receivers could be so good, glad you had a spare tube that appears to be very serviceable. Whats the valve count on this electric beehive?

Thanks Lee - Yes the picture quality is very good - I've been quite amazed myself to be honest. This is the first front projection set I've ever repaired.

As for the valve count, including the tube and the EHT tripler there are 26 valves. Quite a selection really and lots of different valve bases. Octal, B9A, B7G, B8A and whatever that funny connector is called on the CRT.

Thanks old mate and have a tip-top Christmas too.

From Mike.

Mikey405 · 22nd Dec 2015, 10:12 pm

Quote:

Originally Posted by Duke_Nukem

Just occured to me, what did you use to clean the optics?

Hi Jon.

Well I haven't actually cleaned them. The corrector lens on the front looks a little bit grubby inside but it doesn't seem to detract from the picture quality so I was going to leave it. The mirrors look fine but apparently you can clean them if you make up a small "jig" so that they remain aligned with the corrector lens after you've removed the lens from the front. The trader sheet (1118 / T45) tells you all about it but it looks far too much like hard work to me.

Quote:

Guess I'm going to get nagged about a certain Etronic now, no excuses

Perish the thought Jon.

Mikey405 · 22nd Dec 2015, 10:13 pm

Quote:

Originally Posted by Radio Wrangler

I think the cabinet designer must have been the same guy who did the "Stevenson Shield"

It does look like that David (or a bee-hive).

Mikey405 · 22nd Dec 2015, 10:16 pm

Quote:

Originally Posted by julie_m

That test card looks superb! What's the sound like? It appears to have a decent-sized speaker.

I can imagine such a set in use in a gentlemen's drinking establishment ...

Yes indeed. It does look like that kind of a thing Julie. Probably not very practical in most people's living rooms (including mine)...

The sound is very good and loud although the sound circuit isn't anything particularly special. It uses an EF80 / EL41 combination with a fairly big (7" ?) speaker.

Mikey405 · 22nd Dec 2015, 10:20 pm

One thing I forgot to mention in the write-up and possibly it might be unique to White Ibbotson sets (unless anyone knows differently) is that there is no frame hold control in the set. The circuit looks reasonably normal to my simpleton-brain but somebody might be able to shine some light on why it doesn't need a frame hold control...

FERNSEH · 23rd Dec 2015, 1:38 am

Hi Mike,
You are certainly right, there is no frame hold control. Reading through the circuit description of the frame timebase we are informed that it is of unique design. The frame timebase has two controls, VR4 the height control and VR5 the linearity control. VR4 simply adjusts the voltage supplied to the triode section of V11, an ECL80. The slider of the linearity control VR5 is connected to the grid of the pentode section.
Perhaps the unique circuit feature is the way the frame sync pulse is supplied to the frame timebase. The 100 volt negative going frame sync pulse is supplied to the suppressor grid of the pentode section of V11. The text goes on to tell us that the -ve sync pulse causes the pentode to cease conducting which in turn because of the inductance of the primary of the frame output transformer the positive going pulse produced at V11 pentode anode is by means of the feedback capacitor C32 causes the triode section to be turned hard on. The sawtooth forming capacitor C38 is connected across the triode, this capacitor is discharged by the heavily conducting triode, thus the flyback part of the scanning waveform is created.
The ECL80 V11 is essentially a cross coupled mutivibrator. The values of the components will have been calculated so that the free running timebase operates at a repetition rate which is greater than 20mS (50Hz).

These notes apply to the Mark 1 and 2 models.

DFWB.

Peter.N. · 23rd Dec 2015, 11:05 am

The picture quality is far superior to the Philips back projection sets, I think the screen must have degraded the picture. I did have a Decca forward projection set many years ago but disposed of it when we moved down here so never did get it going.

Peter

unitaudio · 23rd Dec 2015, 2:54 pm

It looks like a scaled-down Leslie speaker (a la Hammond organ). What a strange device! There can't be many left. Excellent work and superb write-up, as usual.

Regards,
Paul

FERNSEH · 23rd Dec 2015, 5:27 pm

Quote:

Originally Posted by unitaudio

It looks like a scaled-down Leslie speaker (a la Hammond organ).

That's it, I knew I'd seen something like it elsewhere, the Leslie speaker of course.

DFWB.

Heatercathodeshort · 24th Dec 2015, 9:19 am

I don't think Mummy would have let me have one of these in 1960..
'No! You're not having the thing. Far too big and heavy and it looks dangerous to me!' [Mum usually gave in..] John.

TV_Madness · 29th Dec 2015, 9:59 pm

I missed this for some reason :-(

Excellent write up Mike. I've always found projection sets fascinating.

Brilliant work as per usual!

Matt

Mikey405 · 30th Dec 2015, 3:16 pm

Thanks Matt. My family and I watched an old Norman Wisdom film on it on boxing day and it didn't miss a beat.

Heatercathodeshort · 30th Dec 2015, 4:41 pm

Now that is what 'proper telly' is all about. A real event and something to remember. John.

22nd Dec 2015, 9:55 am	#21
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,903	Re: White Ibbotson Worries I think the cabinet designer must have been the same guy who did the "Stevenson Shield" Though the projection lens porthole gives it the appearance of Captain Nemo's TV set. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

22nd Dec 2015, 10:45 am	#22
Duke_Nukem Octode Join Date: Jan 2003 Location: Birmingham, West Midlands, UK. Posts: 1,268	Re: White Ibbotson Worries Just occured to me, what did you use to clean the optics ? TTFN, Jon

22nd Dec 2015, 9:18 pm	#23
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: White Ibbotson Worries That test card looks superb! What's the sound like? It appears to have a decent-sized speaker. I can imagine such a set in use in a gentlemen's drinking establishment ... __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

22nd Dec 2015, 10:20 pm	#28
Mikey405 Octode Join Date: Jul 2006 Location: Solihull, West Midlands and Beaford, Devon Posts: 1,626	Re: White Ibbotson Worries One thing I forgot to mention in the write-up and possibly it might be unique to White Ibbotson sets (unless anyone knows differently) is that there is no frame hold control in the set. The circuit looks reasonably normal to my simpleton-brain but somebody might be able to shine some light on why it doesn't need a frame hold control... __________________ G7TRF

23rd Dec 2015, 1:38 am	#29
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: White Ibbotson Worries Hi Mike, You are certainly right, there is no frame hold control. Reading through the circuit description of the frame timebase we are informed that it is of unique design. The frame timebase has two controls, VR4 the height control and VR5 the linearity control. VR4 simply adjusts the voltage supplied to the triode section of V11, an ECL80. The slider of the linearity control VR5 is connected to the grid of the pentode section. Perhaps the unique circuit feature is the way the frame sync pulse is supplied to the frame timebase. The 100 volt negative going frame sync pulse is supplied to the suppressor grid of the pentode section of V11. The text goes on to tell us that the -ve sync pulse causes the pentode to cease conducting which in turn because of the inductance of the primary of the frame output transformer the positive going pulse produced at V11 pentode anode is by means of the feedback capacitor C32 causes the triode section to be turned hard on. The sawtooth forming capacitor C38 is connected across the triode, this capacitor is discharged by the heavily conducting triode, thus the flyback part of the scanning waveform is created. The ECL80 V11 is essentially a cross coupled mutivibrator. The values of the components will have been calculated so that the free running timebase operates at a repetition rate which is greater than 20mS (50Hz). These notes apply to the Mark 1 and 2 models. DFWB. Last edited by FERNSEH; 23rd Dec 2015 at 1:50 am.

23rd Dec 2015, 11:05 am	#30
Peter.N. Dekatron Join Date: Jul 2008 Location: Charmouth, Dorset, UK. Posts: 3,601	Re: White Ibbotson Worries The picture quality is far superior to the Philips back projection sets, I think the screen must have degraded the picture. I did have a Decca forward projection set many years ago but disposed of it when we moved down here so never did get it going. Peter

23rd Dec 2015, 2:54 pm	#31
unitaudio Heptode Join Date: Sep 2013 Location: Manchester, UK. Posts: 862	Re: White Ibbotson Worries It looks like a scaled-down Leslie speaker (a la Hammond organ). What a strange device! There can't be many left. Excellent work and superb write-up, as usual. Regards, Paul __________________ ...No, it's not supposed to pick up the World Service, it's not a radio!

24th Dec 2015, 9:19 am	#33
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: White Ibbotson Worries I don't think Mummy would have let me have one of these in 1960.. 'No! You're not having the thing. Far too big and heavy and it looks dangerous to me!' [Mum usually gave in..] John.

29th Dec 2015, 9:59 pm	#34
TV_Madness Pentode Join Date: Jan 2008 Location: Titchfield Common, Hampshire, UK. Posts: 245	Re: White Ibbotson Worries I missed this for some reason :-( Excellent write up Mike. I've always found projection sets fascinating. Brilliant work as per usual! Matt __________________ I don't want anymore junk in this house!

30th Dec 2015, 3:16 pm	#35
Mikey405 Octode Join Date: Jul 2006 Location: Solihull, West Midlands and Beaford, Devon Posts: 1,626	Re: White Ibbotson Worries Thanks Matt. My family and I watched an old Norman Wisdom film on it on boxing day and it didn't miss a beat. __________________ G7TRF

30th Dec 2015, 4:41 pm	#36
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: White Ibbotson Worries Now that is what 'proper telly' is all about. A real event and something to remember. John.