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Old 30th Dec 2011, 8:42 pm   #1
Heatercathodeshort
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Default ETRONIC HV203 10" console. [1949]

This 1949 ETRONIC HV203 has been on my pile of 'to do 'sets for around four years. Time had come to do something about this lazy approach and during the last couple of days I decided to do something about it. The little [?] console receiver was hauled into the workshop with the hope of getting something, if even just a glow from it's CRT.

The Etronic HV203 was manufactured by the Hale Electrical company based in London in 1949. The company appears to have had a very short life failing around 1952 but little actual history is known. They existed pre war but very few products seem to exist in preservation so I guess production numbers were small. They produced a number of television receivers immediately after the war, the first model being a 12" console model ST12 with mains derived EHT supply. They appear to have been well constructed as were their radiograms.

The HV203 is a neat console with a ten inch Cossor 108K picture tube. It is designed to work from AC mains, a transformer being fitted to supply valve and CRT heater current. The massive Cossor 53-KU H.T. rectifier valve is fed from the primary of the mains transformer thus rendering the chassis live, so all the usual precautions regarding AC/DC technique have to be taken into consideration when servicing. The Cossor company certainly had a strong influence on the design of this receiver supplying all the valves and the CRT. It has similarities to the Cossor 916 series but only similarities.

The TRF receiver unit is mounted separately on an angle to the main chassis with three 4BA self tapping screws. It can be removed for service work as the connecting leads are long enough to allow this, a nice touch. The unit employs B7G based 6AM6 valves [EF91, W77, CV4014, 6F12] for vision and sound amplification and another for sound output, quite a common occurrence with early AC/DC television receiver design. Used as an audio output valve you would think it would deliver a poor performance! Think again, that little valve delivers a huge amount of non distorted sound. Maybe I should re badge a few as mini PX25's and make a few bob..

The timebases are somewhat strange, more in valve types than circuit complexity. The line timebase is of the self oscillating type employing a 807 high power tetrode of WW2 fame on a UX5 pin base. EHT is derived from the flyback pulse and a EY51 EHT rectifier. The LOPT is a very early flyback type of strange construction dipped in pitch.
The frame timebase is fairly conventional using a 7C5 Cossor valve for frame output which is basically a 6V6GT on a loctal base. Now here comes the weird bit. Another 7C5 is used as a blocking oscillator. Why they used the EF91 for sound output and a 7C5 for frame oscillator we will never know but this is what I enjoy with these quirky receivers. Much more interesting than a TV22.

A quick inspection showed the chassis to be very original and probably laid to rest around 1959. I do not have a circuit for this particular model so had to trace out the relevant sections as I progressed. In an attempt to find the mains filter capacitor I traced the mains lead from the switch to the underside of the mains transformer and then to the unused tags of the H.T. rectifier valve Nasty! I don't like this method of construction and it can lead to valve base leaks and odd symptoms. The usual waxie .1uf was in fact a.002uf in this model and it was clipped out of circuit to prevent an unwanted display of party poppers.

With the mains applied the valves lit followed by the familiar buzz of the frame output transformer. A few seconds later a line whistle could be heard but this soon died leaving just the frame buzz for company. There is only one capacitor employed in the self oscillating circuit providing feedback from the line output stage to the grid of the 807. It was a big fat waxie that was printed .5uf but was in fact a 100k resistor in disguise. Replacing this resulted in a constant line whistle but still no 'first light'.

Attention was directed towards the line output section and a spark test was carried out between the tube anode and chassis. Nothing! The EY51 was not lit but a small spark could be obtained from the single wire anode. You have guessed it..Hidden just under the tube bowl was that brown Bakelite thing called a VISCONOL EHT smoothing capacitor. Unhooking its top connection from the EHT supply resulted in the EY51 fully heating producing full AC at it's anode and Healthy EHT at the cathode. The resulting spark test startled me somewhat as I was not expecting such a good result. Still no screen illumination! The Cossor 108K is a very reliable tube and I doubted it would have zero emission. It is one of the very first tubes to employ an ion trap, a device invented by Cossor themselves but the magnet on this tube was covered in dust and had obviously not been slipped out of adjustment.

Next a quick check was made on the tube electrode voltages. It is a simple triode with a strange base with four 'wander' sockets' for heaters grid and cathode. No grid voltage could be detected with the AVO8 so the wire was traced back to the slider of the brilliance control. This was decoupled to earth with the usual .1uf wax capacitor that read exactly 10k on the meter. With a replacement fitted the screen fired into life with a very distorted 'first light'. It is very bright and the future looks good. It is going to be a marathon waxie changing saga. There are dozens of them..We will see.
To be continued. John.
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Old 30th Dec 2011, 10:17 pm   #2
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Default Re: ETRONIC HV203 10" console. [1949]

Enjoyable read as ever John, nice to see the old tube wearing its string vest!

Any pics of said 'first light'?

Greg
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Old 31st Dec 2011, 12:13 am   #3
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Default Re: ETRONIC HV203 10" console. [1949]

Agreed. A very enjoyable first chapter and if I'm not mistaken, is there not some illumination around the edge of the CRT in picture 2?
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Old 31st Dec 2011, 12:23 am   #4
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Default Re: ETRONIC HV203 10" console. [1949]

Indeed there is, I've always had a soft spot for Etronic equipment as one of the first valve radios I got was an Etronic, I've always had a hankering for an Etronic tv but they don't come on the market that often.
Looking forward to seeing an image on the screen.

Jay
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Old 31st Dec 2011, 12:26 am   #5
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Default Re: ETRONIC HV203 10" console. [1949]

Wow this is a true jem with the valve line up . Go on get it done before the new year and lets al see pictures of this set doing its stuff. Danny
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Old 31st Dec 2011, 8:33 am   #6
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Default Re: ETRONIC HV203 10" console. [1949]

It looks promising so far. I note the chassis is a triangular shape, just like the Pye LV51 I am working on at the moment.

I love the sock on the CRT, presumably to contain the glass if (when) it implodes!
Nice to know that the LOPT is ok, there is something very appealing about single channel sets of this era. I will be watching your progress with great interest.

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Old 31st Dec 2011, 10:22 am   #7
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Default Re: ETRONIC HV203 10" console. [1949]

Yes that illumination is indeed 'first light' after disconnecting the Visconol and wiring in a 10kv replacement. I will sort the pictures and let you see the first signs of success and hopefully if I can find the time this afternoon, some sort of picture. John.
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Old 31st Dec 2011, 12:02 pm   #8
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Default Re: ETRONIC HV203 10" console. [1949]

Quote:
Originally Posted by mark pirate View Post
I love the sock on the crt, presumably to contain the glass if (when) it implodes!
I'm not sure it would contain the glass though, I may be wrong but I bet that thing would go off like a grenade if it did let go! Still it's lasted this long so hopefully it'll last forever!

Great write-up John, looking forward to the next instalment and some more pictures. Amazing to see something that's been asleep for over 50 years being slowly woken up!
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Old 31st Dec 2011, 3:57 pm   #9
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Default Re: ETRONIC HV203 10" console. [1949]

Excellent to see a rarer brand being brought back to life. John, I totally agree that these oddballs and little known sets are what its all about, and will help to stretch our grey matter a little.
I seem to remember Chas E Miller writing an article under the occasional 'Vintage TV' heading in 'Television' magazine many years ago regarding a receiver manufactured by Hale Electrical Co. I don't remember what model it was, but seem to recall that the chassis was made up from surplus parts, so this could have been an early post war set.

Looking forward to the next instalment.

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Old 31st Dec 2011, 7:18 pm   #10
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Default Re: ETRONIC HV203 10" console. [1949]

great post, look forward to reading more. Can we see some pics of the underside of the chassis please.

Steve
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Old 31st Dec 2011, 10:44 pm   #11
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Default Re: ETRONIC HV203 10" console. [1949]

Who opened Pandora's box?

The saga continues. I have posted the original pictures of the chassis after removing it from the cabinet after 50 years or so of slumber.
Note the thick film of static dust on the face of the tube. Picture must have been a bit hazy looking through that lot. Smoking and coal fires have certainly done their worst.

The first picture shows the first light after turning the chassis around.
It is very bright the reasons for which will become obvious from the second picture showing the EF91 video output valve with a massive amount of oscillatory voltage on it's poor control grid. Poor thing looks a bit over driven.The cause of this is due to breakdown of the decoupling capacitors mainly on the screen grids of the TRF amplifiers.

There are four .005uf waxies per stage making a tidy number to replace. The whole strip bursts into oscillation producing a massive signal at the vision detector. I decided to remove the final vision amplifier valve and attempt to make some progress with the raster shape.
The blocking oscillator transformer had been replaced in the 1950's together with the output valves bias capacitor so I made a start on replacing the capacitors in the frame stage. All were of good TCC make but of course the wax had become waterlogged over the past half century and all had to be replaced. This resulted in a reasonable raster but the rear sliders controlling height and frame linearity were useless and temporary miniature Ekco pots of the same vintage were wired in allowing the timebase to be evaluated. With the scan coils straightened and the three centering screws correctly set the raster looks very good.

The next job is to tackle that R.F. strip and see if it is capable of amplifying a 45mc/s signal without shrieking it's head off. The tube is only a little 10" 108K baby. Nothing to be scared of despite it's formidable looking anti implosion protection. [Long before the days of rimbands, Ha ha!] I thought we had toughened up all the 'Wendy Woos' scared of telly tubes by now..
Be patient, guys. More to come.

John.
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Old 31st Dec 2011, 10:49 pm   #12
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Default Re: ETRONIC HV203 10" console. [1949]

Another two pictures showing the dirty screen and underside. J.
PS. The third pic is my secret agent. [Just to keep the pussy guys awake.]
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Old 31st Dec 2011, 10:51 pm   #13
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Default Re: ETRONIC HV203 10" console. [1949]

Wow, that EF91 is certainly sweating well!
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Old 1st Jan 2012, 10:29 am   #14
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Default Re: ETRONIC HV203 10" console. [1949]

Amazing what you can do with an EF91.

It's looking good, John.
The only one of this make I've ever seen was a projection, if I recall. Can't wait to see a test card on-screen.

Like your B-Y cat!
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Old 1st Jan 2012, 1:16 pm   #15
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Default Re: ETRONIC HV203 10" console. [1949]

That mains tx looks Identical to the the ones used in Etronic radios right down to the press studs used to select the mains input voltage. Work seems to be progressing well, not long now before we see Test Card C on it.

Jay
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Old 1st Jan 2012, 1:19 pm   #16
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Default Re: ETRONIC HV203 10" console. [1949]

Quote:
Originally Posted by Mike Phelan View Post
Like your B-Y cat!
Unless John has been out catnapping it's not his cat. Sherry (for that is her name) lives with Gerry at the Museum in Dulwich.
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Old 1st Jan 2012, 2:10 pm   #17
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Default Re: ETRONIC HV203 10" console. [1949]

The article Chas Miller wrote on the Etronic brand appeared in the September 1981 issue of Television magazine. The article mainly covered the ECV1523 & ECV1527 which were 10" & 12" consoles.

There were London and Birmingham versions but the chassis layout appears to be the same as John's chassis and still uses two 7C5 valves but they had swapped the 807 line output valve for an EL38.

Really enjoying reading your restoration of this set John and it's really interesting to hear about the less well known sets .
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Old 1st Jan 2012, 11:03 pm   #18
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Default Re: ETRONIC HV203 10" console. [1949]

Good read so far John,

That EF91 sure looks a little hot under the collar!!
I like the quirkiness of using the EF91 as an audio o/p bottle, kind of reminds me of the Thorn 980 chassis using the EF80 IIRC.

Looking forward to the next instalment, all the best!

Cheers
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Old 2nd Jan 2012, 10:49 am   #19
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Default Re: ETRONIC HV203 10" console. [1949]

Hello Lee,
I don't know, after all my efforts at enlightening you young lads to the delights of 405 television receivers. When did the PCF80 triode/pentode turn into a EF80 screened pentode? Answers on a post card please.

I spent a considerable time recapping the R.F. unit on the Etronic. There are four capacitors, .005uf per amplifying stage on both sound and vision. Heater, screen grid, anode supply and cathode. They were all leaking heavily and the ones connected to the H.T. supply turned into frying sausages literally in front of my very eyes. I clipped them off in turn as they bubbled away while working on the frame timebase. They almost won the race but I'm an ace with the side cutters.
I fitted nice ceramic types with a lower value actually .001uf. The vast majority of TRF strips use this value with complete stability and as I had a reasonable stock they were put into service. Switching on resulted in complete calmness, even the EF91 video output valve stopped showing off and the application of a signal from the Aurora resulted, after adjustment to the contrast and gain controls, the results you see in the pictures. The frame sync was very weak and could just about be locked with very critical adjustment to the front mounted control. The original waxie sync chain capacitors had all been replaced but a check with the scope revealed a very low level pulse at the screen grid of the frame oscillator. Tracing the circuit showed a .1uf connected from the sync input to earth, a very high value that resulted in 90% of the sync pulses being shunted to earth. The circuit is very basic lacking an interlace filter as such. Replacing this capacitor with a .047uf resulted in solid sync that remains locked for an extended period. All very odd as the receiver must have operated ok with the original .1uf which is still sitting on the bench..
After about a minute there was a snap and the nasty sound of an H.T. overload. The picture reduced in size considerably and the sound completely vanished. That was the clue..After investigation it was discovered that the tone correction capacitor, yet another .005uf waxie was connected from the anode of the sound output valve EF91 to chassis rather than across the primary of the audio output transformer which is a more common practise. It was hidden away under some wiring but was soon extracted and a replacement fitted. I then washed my hands in petrol to remove all traces of wax slime, similar I guess to a police surgeon after carrying out an autopsy.
The results are very good made possible by the excellent Cossor 108K picture tube. Cossor were a most under recognized company producing some of the best valves and CRT's of the period. The same could be said of many superb British companies the names of which have faded from the technical pages over the last 50 years.
The line linearity is very poor on the test card and I must admit I have cast a very suspicious eye at the rather odd LOPT. It is getting slightly warm and the pitch covering appears to be loosening from the windings probably caused by a shorted turn on the primary rather than EHT winding. It looks a fairly easy job to rewind should it fail as the pitch it was dipped in back in 1949 is almost completely detached from the bobbin.
I have a Douglas/AVO wave winder, in fact the very one I used as a school lad. I overhauled it a year or so back and it works well but it lacks the wire reel holder and tension arrangement. I can't remember what it looks like but will no doubt be able to take a few pictures of one that is rigged up and working. I must mount this on a board complete with the motor and make use of it. I think it will be my project for the coming year or at least one of them.
We will see if the LOPT holds up over the next few days. The devil is sitting on my shoulder. All the best for 2012, John.
PS. Yes Jeffrey, the pussy cat is indeed Sherry from the VWM.
Regards, John.
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Old 2nd Jan 2012, 3:31 pm   #20
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Default Re: ETRONIC HV203 10" console. [1949]

Quote:
Originally Posted by Heatercathodeshort View Post
Tracing the circuit showed a .1uf connected from the sync input to earth, a very high value that resulted in 90% of the sync pulses being shunted to earth. Replacing this capacitor with a .047uf resulted in solid sync. All very odd as the receiver must have operated ok with the original .1uf which is still sitting on the bench.
Now that's exactly the sort of thing that sorts out those with a decent grounding in proper television theory from nits like me who would have hit a dead end there and run away sobbing like a schoolgirl.

I mean if you can't trust what the manufacturers put in 'em then what hope is there?

Steve J
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