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Old 22nd Sep 2017, 5:03 pm   #61
Heatercathodeshort
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Default Re: And the next one! a GEC BT2147

Without doubt, the resistor experts. J.
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Old 22nd Sep 2017, 11:03 pm   #62
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Default Re: And the next one! a GEC BT2147

Quote:
Originally Posted by Heatercathodeshort View Post
To be honest there is little skill involved with a receiver of this type. Being able to follow a circuit diagram and component layout is 60% of the task.
Watch any 'Master' of their craft and they will make it look effortless and easy! One of the great things about this community is the skill and knowledge that people contribute- especially some of the older folk who were actually there on the ground when these sets were new
So I would echo Matt's praise of your work to resurrect this set- 'well done sir'!!
All the best,
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Old 23rd Sep 2017, 7:52 am   #63
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Default Re: And the next one! a GEC BT2147

It ain't finished yet till the fat lady sings!

Seriously thanks for your very kind comments. I'm not worthy! It's more of a 'knack' than skill.
Kind regards, John.
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Old 23rd Sep 2017, 8:42 am   #64
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Default Re: And the next one! a GEC BT2147

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Originally Posted by Heatercathodeshort View Post

I must admit, bringing these old receivers back to life is a little like walking in dead mans [and women's] shoes. Everyone involved with this receiver, built at the Coventry works of GEC is unlikely to be still with us. The design office, assembly line, testing, packing, transport and finally the agent that sold it to his very lucky customer, now just a memory as are most of the shops and the factory that built it!
I hope I'm not straying too OT here.

This quote sums up so well one of the reasons why I love finding and trying to resurrect old TVs. Being able to connect to the past in a way not possible by merely visiting a museum or web site. To someone born in 1969 these sets really do come from another world and I hope we try and save some of the consumer electronics of the past for future generations. A tribute to the hard work and ingenuity of these people, and a little but important 'two fingers' to the throwaway 'culture'.
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Old 26th Sep 2017, 7:14 pm   #65
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Default Re: And the next one! a GEC BT2147

Hi John and Matt,
that's a great result in the end.
I had a very good look and am 99.9% certain that I must have disposed of my spare Brummy GEC RF unit a few years ago.

I wouldn't mind having a go at back converting the RF unit you have there though. I like a challenge. Those proximity coupled inductors are a nice touch, a bit like the PYE LV30 which in my mind is the ultimate TRF design...

Cheers
Andy
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Old 26th Sep 2017, 8:50 pm   #66
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Default Re: And the next one! a GEC BT2147

Might be difficult with this unit Andy. It appears to be a purpose built IF unit. There are no holes drilled for the RF/Mixer bit! Could be done of course but it's a labour of love of course.

I guess GEC could produce a simple I.F. unit in less time than it took to strip and modify the originals. I expect demand overpowered the time factor.

Got the busy weekend over and with a bit of luck will install the new pot panel.

I will then investigate the tuner. Regards, John.
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Old 27th Sep 2017, 9:17 pm   #67
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Default Re: And the next one! a GEC BT2147

Thanks for your very generous offer Andy, it would be great to return the set to its original spec one day. For the time being I'll run the GEC with whatever tuner John chooses, but as the rf deck is easily removable I will certainly keep this in mind for a future project.
I'm looking forward to having a play with it myself and reinstating it in its cabinet, once I've sorted the mask out!
John you are way too modest!!! I never expected you to go as far as you have done with the set. I'll be forever in your pocket after this!!

My kindest regards to you both

Matt
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Old 30th Sep 2017, 9:26 am   #68
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Default Re: And the next one! a GEC BT2147

With the new control panel in place [definitely not a job for Interlace] and wired up [urghhhh!] we were getting to the final conclusion of the 'Bakelite Bitch.'

Some small control knobs were sorted and filed down to allow their grub screws to contact the very short spindles on the new presets.
A good test card was displayed with all controls set mid way.

Attention was directed towards the sound or rather complete lack of it. Turning the volume control to minimum resulted in an almost dead HT short!
Metering the control grid voltage on the N78 audio output valve showed the full HT voltage...To cut a long story short the valve has a screen grid/control grid dead S/C. A visit to the valve store will be required.
I usually send Interlace into the loft to sort through the boxes but he is scared of spiders and usually grabs the first valve he sees and returns with everything but the valve you require.
How can you mistake a PX25 for the tiny N78?

Once the sound is sorted it should be about complete. Just a more suitable tuner and I think I know where one is lurking.

The pictures show the rebuilt under chassis and the control panel wiring. Space is very tight!

The last episode soon. [Ha ha!] Regards, John.
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Old 30th Sep 2017, 3:56 pm   #69
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Default Re: And the next one! a GEC BT2147

A little more progress. The output valve by the way is an N37 not an N78 as mentioned earlier.

I hunted through my valve stock but gave it up as a bad job. I have a couple somewhere but 'somewhere' refuses to load into my SatNav.

I decided to make up an adapter that even David would be proud of. Simply a B7G plug and a B9A valve base cross wired to take a PL82.

We now have good sound but too much, due to being uncontrollable. The dead short in the N37 has blown the bottom end of the volume control O/C....

Oh no! The dreaded pot boxes will have to be tipped out to find something suitable.
It's a job for Interlace but he says he can't read the small print resistance information despite me spending a huge sum on designer glasses for him. Oh well tomorrow is another day. Regards, John.
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Old 5th Oct 2017, 5:08 pm   #70
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Default Re: And the next one! a GEC BT2147

I think I have gone about as far with the Bakelite Bitch that a sensible approach will allow. OK I could have removed all the components and done a chassis referb but little would be gained and all the originality would have been lost.

As it is, I have had to replace the slider bank with conventional rotary controls together with a large number of passive components but it is 68 years old!

I have wired into circuit a Plessey tuner removed from a scrap Puratone 17" table model. It is quite happy in it's new role and will serve for experimental purposes until another suitable receiver unit can be discovered [and it will].

The IF plate fits well into it's original slot in the main frame so no modifications required. For one moment I had horrors of the replacement FOPT fouling but no worries as there is plenty of room.

Believe it or not it was a lot of fun but I had to take it in small doses to ensure success [and my sanity].

OK Matt, the Bakelite Bitch is all yours! Ha ha! John.

Pictures taken this morning.
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Old 5th Oct 2017, 6:07 pm   #71
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Default Re: And the next one! a GEC BT2147

Nice job as always John.
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Old 5th Oct 2017, 8:09 pm   #72
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Default Re: And the next one! a GEC BT2147

Top marks for effort! I hope your pottery cats weren't temped to nibble on those wirewound doughnuts!

Reminds me of Tim Hunkin who likes to decorate his pcbs with plastic men from model train sets.
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Old 5th Oct 2017, 8:31 pm   #73
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Default Re: And the next one! a GEC BT2147

Hi John,

In a word, Impressed!!! I'm very very pleased with how the bakelite bitch has turned out. Those pictures look fantastic! I really hope your sanity has survived unscathed! I'll Pm you and we'll make a date for a visit. A big thankyou for everything (so far!)

Matt
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Old 5th Oct 2017, 8:42 pm   #74
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Default Re: And the next one! a GEC BT2147

there's a wee snippet of film from a GEC tv factory here, among others.

https://www.youtube.com/watch?v=uH726tE1knA
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Old 5th Oct 2017, 8:57 pm   #75
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Default Re: And the next one! a GEC BT2147

That is a brilliant film Kevin I've got the full BVWS dvd. Always fancied restoring one of these sets. I very nearly bought one at the last nvcf but the chap in front of me beat me to it!
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Old 5th Oct 2017, 9:02 pm   #76
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Default Re: And the next one! a GEC BT2147

Quote:
Originally Posted by McMurdo View Post
there's a wee snippet of film from a GEC tv factory here, among others.

https://www.youtube.com/watch?v=uH726tE1knA
Did you notice how fast the human assemblers' hand movements were? It is almost as if the film was speeded up, a bit like when you see early silent films (filmed at 16fps) shown at 24fps!
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Old 5th Oct 2017, 9:44 pm   #77
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Default Re: And the next one! a GEC BT2147

The Rank Bush Murphy film is certainly running about 20% too fast. Although even at normal speed those women must have gone like lightning. How many could they turn out in a day I wonder?
Although I love old tellies, I think if I had to sit on a line and put the same bits of them together all day I'd seriously want to kill myself by home time.
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Old 5th Oct 2017, 10:01 pm   #78
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Default Re: And the next one! a GEC BT2147

My first work experience was on a production line soldering SMD and winding inductors. The girls there worked just as fast, hands almost a blur.

I've got one of those bakelite b**'s waiting for me on the shelf.
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Old 6th Oct 2017, 8:19 am   #79
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Default Re: And the next one! a GEC BT2147

Don't be put off by this thread! This example was a basket case having been stored in very bad conditions with the complication of the modifications required for Band 3.

The BT2147 series, and this covers are very large number of models, is very straightforward and capable of excellent results with a good standard of reliability.

The only black hole is the flat faced GEC tube type 6505A. It tends to develop heater faults mainly lowering it's resistance together with an O/C cathode connection.

Being flat faced it is difficult to replace from a mechanical aspect with a conventional Mullard MW22-14/16/18 9" type.

This could possibly be overcome with the BT2147 due to the CRT faceplate being spaced a little from the implosion protection screen. The earlier BT1091 is almost touching it so no room for modification here.

The Mullard tubes ar also tetrodes requiring a first anode voltage of around 300v. No problem obtaining this potential from the chassis but they also require a much reduced focusing field needing shunts to be fitted across the focus magnet. [See my Ekco T164 restoration]

Other than the CRT difficulty no problems should be experienced.

I have the full service manual available should you require it.

My pet Orangutan 'Interlace' has been instructed to search all Forum friends vehicles for any Bakelite 'Oh what a lovely cabinet' models and direct their vehicles back onto the A29 or he may pelt you with duff U801's...

Regards as always, John.
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Old 12th Oct 2017, 9:14 pm   #80
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Default Re: And the next one! a GEC BT2147

A brilliant end result. I hope to get something similar soon to have a go at.

Regards, Robin.
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