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RGD Deep 17.

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Till Eulenspiegel
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This is the set that was advertised as "tested in the Tyne-Tees Television region". That was late 1958 when the test transmissions started for the new ITV station for the North-East of England.

The RGD Deep 17 was one the most reliable sets ever made. The example we have here doesn't require to much work to return it to it's full potential. The CRT is the excellent Mullard AW43-80 and is one of the best monochrome tubes.

RGD Deep 17

 

Looking for a channel selector knob.

Till Eulenspiegel.

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Topic starter Posted : 27/10/2019 8:44 pm
PYE625
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Reading the sales brochure, I couldn't help wondering how the "In-built automatic focusing" works.

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Posted : 27/10/2019 9:17 pm
turretslug
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Good luck with that set Till, for some reason I rather like the "cube" or "posh tea-chest" presentation of this era of TV sets. It looks like a nice piece of furniture too, with not a lot of TLC it should really look excellent- it's very emblematic of the time and also makes for an instructive contrast (!) with the current hang-on-the-wall picture-frame TVs. I'm sure that one of my old physics teachers had one of these amongst the collection of '50s and '60's sets dotted around the perimeter of the physics lab (early '80s- bit late to try and pinch a selector knob from it now....)

How sturdy is the case?- I wonder if the possibility of someone sitting on what must have seemed a tempting perch to some occurred to the designers. Also, whilst easy on the eye, I wonder if this deep-case format could be a heat-trap.

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Posted : 27/10/2019 9:41 pm
Till Eulenspiegel
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Hi Andrew,

I suppose one could say that the AW43-80 CRT has built in automatic focus but the same tube was used by many other manufactures. Certainly all those signed up to Mullard so that included Ferguson and the other two Thorn brands as well as Bush, Alba, Decca, Pye and other less well brands such as Beethoven and Raymond. The chassis in the Deep 17 was also fitted in the Regentone TR177.  Both sets were designed and made in the Romford works.

Till Eulenspiegel.

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Topic starter Posted : 27/10/2019 9:51 pm
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Till Eulenspiegel
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Hi Turretslug,

The cabinet is quite a robust affair and was used for an earlier model called "The 17".   Whereas the Deep 17 is a quite simple set the "The 17" is a full specification model having gated vision AGC and flywheel line sync. The Regentone TT7 was electrically similar to the RGD "The 17".  Both sets were made in the Regentone works in Romford.

Till Eulenspiegel.

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Topic starter Posted : 27/10/2019 10:05 pm
PYE625
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Seeing this set and reading about the above mentioned AW43-80 persuaded me to fire up the Defiant set I have. (Pleased to say that set is working well).

I am really looking forward to see how the RGD set responds Till.

If you remember, I was very fortunate to aquire a replacement Mullard CRT for the expired Mazda in the Defiant set. I can't believe it is a year ago already !

https://www.radios-tv.co.uk/community/black-white-tvs/defiant-7109/paged/8/#post-93657

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Posted : 27/10/2019 10:27 pm
Till Eulenspiegel
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The Defiant set was fitted with either Mazda CRM173 magnetic focus or the CME1702 electrostatic tubes.  The Mullard AW43-80 was also used in some other Plessey 90 degree chassis so as you say it is perfectly at home in the Defiant.

Looks like as if it's always been in the set.

Till Eulenspiegel.

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Topic starter Posted : 27/10/2019 10:55 pm
Marconi_MPT4
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Looking forward to see how your RGD Deep 17 restoration progresses.

Way back in the 1970's an acquaintance had one of these left to him from a family estate. It was working and he used it for a while. One day it failed and he said to come round and pick it up. In the meantime he then decided to keep the cabinet and speaker just presenting me a 'complete' chassis and CRT  ? No knobs, these had already been recycled! When I finally had a look underneath the main smoothing capacitor block was missing but eventually I did manage to win that back as it was still in a box on top of his coal bunker. When I finally reassembled it and powered up, the PL81 just glowed a menacing red and this symptom was eventually found to be caused by a faulty line output transformer.

Sadly this chassis was scrapped for spares, but the Mullard red label 'Radiant Screen' AW43-80 gave sterling service in another set. Operated within specification these CRT's appear to have a very long life expectancy.

Thinking back however, some line drive was present at PL81 control grid, but was the line oscillator circuit formed by cross coupling the line output stage back into something like an ECL80 triode?

Rich

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Posted : 28/10/2019 2:53 pm
Till Eulenspiegel
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Well at last after all the usual interruptions in this awful shop I've made a start on the set.  As the attachment shows the Mullard AW43-80  CRT is really bright and the only real issues are in the frame timebase. The vertical sync could be better and the HT smoothing is not too good.

RGD Deep17 2

 

The basic design of the Deep 17 was carried forward into the Regentone Ten 4 and the Ten 17 models.

Till Eulenspiegel.

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Topic starter Posted : 28/10/2019 6:03 pm
PYE625
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Crikey, that was quick ? 

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Posted : 28/10/2019 6:15 pm
Till Eulenspiegel
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The Frame output valve (PCL82) is slow warming up and will be replaced.

Note the frame sync pulse integrator components R70, R71 and C78.  The amplitude of the integrated sync pulse train will have a low amplitude at the junction of these components. Let's see what the oscilloscope reveals.

Till Eulenspiegel.

RGD Deep 17 3

 

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Topic starter Posted : 28/10/2019 10:10 pm
Till Eulenspiegel
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The set I'm working on is the later production chassis which has a redesigned frame timebase. This became all too evident when the under chassis circuits were examined. The interlace diode is omitted and the sync separator is now an ECL80 instead of a PCF80. The frame oscillator is a cross coupled multi-vibrator instead of the cathode coupled circuit in the earlier sets.  The frame sync is supplied to the oscillator by the differentiator capacitor C59.

The frame timebase circuit in the attachment is from the Deep17FM.

RGD Deep17 later FTB
RGD Deep17 under chassis

 

Till Eulenspiegel.

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Topic starter Posted : 30/10/2019 9:47 pm
Nuvistor and PYE625 liked
Till Eulenspiegel
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Can't sign this job off because the interlace is bad.  As mentioned in my previous post the later production Deep 17 uses a differentiator capacitor to couple the frame sync pulses to the oscillator.   The 'scope waveform shows the partially integrated frame sync pulse train.  The sync pulses have a fast leading edge rise time but the trailing edge is delayed no doubt due to stray capacitances in the circuit.  The series resistor R71 (680Kohms) must have some function in the synchronising of the oscillator because a resistor of the same value is present in a similar circuit employed in certain Ferguson sets of the same period the Deep17 was made.

The best plan will be to stop the frame oscillator and examine the waveform at the grid of the triode section of the ECL80. (Pin 2 V7T)

Till Eulenspiegel.

RGD Deep17 sync

 

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Topic starter Posted : 06/11/2019 10:54 pm
Till Eulenspiegel
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Stopped the frame oscillator by grounding pin 1 of the triode section of the PCL82  frame oscillator and output valve, V14T.

The oscilloscope traces were taken from the triode grid of the ECL80 frame oscillator, V7T.   The odd and even fields can clearly be seen at the beginning of the negative going sync pulse.   The positive going trailing edge of the differentiated frame pulse train is suppressed by conduction between the grid and cathode of the triode.

It is now clear why the interlace is bad in this set. There is too much 50Hz ripple on the HT supply. A new smoothing capacitor will be fitted.

Deep17Field sync 1
Deep17Field sync 2

 

Till Eulenspiegel. 

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Topic starter Posted : 10/11/2019 1:54 am
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Nuvistor
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Does the ripple show on the picture in other ways apart from poor interlace?

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Posted : 10/11/2019 11:24 am
peterscott
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Interesting scope pics.

Peter ? 

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Posted : 10/11/2019 11:41 am
Till Eulenspiegel
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Posted by: @nuvistor

Does the ripple show on the picture in other ways apart from poor interlace?

Hi Frank,     indeed it does, the picture "breathes" and as it does the picture can on occasions be seen to drift in and out of near perfect interlacing. But most of the time the picture looks liny because the CRT has such sharp focus. Hopefully, a new smoothing capacitor will solve the problem. 

Hi Peter, the half line difference can be seen at the end of the odd field and the full line at the end of the even field.  I hope I've the odds and evens right.

Just to confirm the frame sync pulse is truly differentiated I'll disconnect the grid connection to the ECL80 triode section.

Till Eulenspiegel. 

  

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Topic starter Posted : 10/11/2019 1:56 pm
Till Eulenspiegel
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The grid wire to V7T is cut and the 'scope connected to the junction of the 150pF sync coupling capacitor C59 and R70. The negative going leading edge of the frame sync pulse is unchanged from the tests taken two days ago. There is a slight lift of the positive going trailing edge but not as much as I would have expected with the oscillator valve grid disconnected.

But the instantaneous output from a CR differentiator is a function of the rise time of the pulse and in the RGD the leading edge of the frame sync pulse has a fairly fast rise time but it is not so with the trailing edge.  

The HT smoothing capacitor will be replaced today. 

Deep17Field sync 3

Till Eulenspiegel.

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Topic starter Posted : 11/11/2019 11:13 am
Till Eulenspiegel
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Replaced the HT  smoothing capacitor and now the max 50Hz ripple on the HT line is <1V P - P, that's a lot better than the 7V P - P it was with the old smoothing can.

Now the interlace is a lot better, but the setting of the frame hold is a bit critical for perfect interlace. 

Till Eulenspiegel.

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Topic starter Posted : 11/11/2019 4:19 pm
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Nuvistor
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I seem to remember with some early sets that it was suggested to use the frame hold to adjust the frame to lock then fine “tune” for best interlace, could this be one of those circuits?

 

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Posted : 11/11/2019 9:08 pm
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