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Old 20th May 2015, 3:38 pm   #1
dazzlevision
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Default The GEC BT342 television receiver, with VHF/FM radio facility.

Hello,

I thought you might like to see the innards and cabinet of one model in the final range of true GEC designed and built television receivers, the BT342. This BT342 came to me “for spares”, having a severely disintegrating and very tatty cabinet, no back cover, no LOPT/EHT rectifier compartment cover and the wrong timebase PCB fitted (it’s actually from a BT302). Luckily, I already have a restored and complete BT342 in good cosmetic condition.

The BT342 is a 19” set with VHF/FM radio built in and was, I think, made in 1961-2.

There were three basic models in this range: BT336 (a 19” table model), BT346 (a 23” consolette model on a stand) and BT342 (the only one with VHF/FM radio). The two “TV only” models could also be supplied with an extra common sound and vision IF amplifier stage, for use in fringe areas (and they were then given a different model number).

The main chassis is very similar to the earlier and familiar bow fronted 17” and 21” GEC TVs, starting with the BT302. However, this last true GEC TV range incorporated a “piano key” style of VHF TV tuner. It was made by AB Metal Products and employs 30L15 and 30C15 frame grid valves, which provide greater sensitivity. The left hand side customer controls also feature four piano keys, to provide symmetry in the cabinet presentation. Their functions are: on-off, sharp picture, soft picture and treble cut.

VHF/FM radio is provided by an entirely separate VHF radio tuner unit (PCC85) with two stages of IF amplification (EF85 + 6F23) followed by an EB91 FM detector.

The Mazda CME1901 CRT tested borderline on my CRT tester, but I decided to try and get the set going, in order to subjectively assess the CRT’s condition whilst showing a picture (and to get an idea of what else was wrong with the electronics).

You will see that I have replaced many Hunts “Moldseal” metallised paper capacitors, two Hunts wax capacitors and the original Hunts HT reservoir/smoothing “can” electrolytic. These replacements are “lash ups” as I wasn’t intending to fully restore the chassis, rather do just enough to get a picture on the CRT.

In fact, the CRT seems reasonable, albeit with a somewhat smeary Test Card C.

As a result of the GEC and Radio & Allied Industries (Sobell) merger that took place in 1961, this long standing GEC cabinet and chassis design was jettisoned with the next range of GEC badged sets, in favour of a Sobell design. However, the first range of “Sobellised” GEC sets did retain some GEC features, such as single sided PCBs, the use of Mazda type valves and a blocking oscillator in the line timebase (rather than the typical Sobell multivibrator).

Regards,

Dazzlevision
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Old 20th May 2015, 3:41 pm   #2
dazzlevision
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Some more pictures
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Old 20th May 2015, 3:53 pm   #3
dazzlevision
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Here is a scan of the front cover of the GEC service manual for this range of sets. You will see that the address is GEC (Radio & Television) Ltd, Langley Park, Slough and not The General Electric Co Ltd, Magnet House, Kingsway, London. This reflects the merger of the GEC and Radio & Allied Industries radio and TV set manufacturing operations (Radio & Allied/Sobell was based in Langley Park, Slough).

Regards,

Dazzlevision
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File Type: pdf GEC BT342 etc service manual front cover.pdf (542.4 KB, 130 views)
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Old 20th May 2015, 4:50 pm   #4
mark pirate
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

It is certainly worth restoring, I have taken on a lot worse!
I am sure some similar material can be found to tidy up the front panels, although making a new back could be a bit of a challenge.
The tube will probably improve when it has been used for a few hours, this was certainly the case with my Pye V210.

Mark
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Old 20th May 2015, 8:32 pm   #5
dazzlevision
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Hello,

I've noticed the LOPT has been replaced in the past. I have checked the dc resistance of the windings against the values given in the service manual and it isn't the correct LOPT for the BT342. It also shows the usual failure mode of most pitch dipped LOPTs - boost HT gradually reduces with time and the EHT overwind gets hot.

The CRT base pins are corroded at the point where they meet the glass neck and I fear this may lead to loss of vacuum in time.

Taking all this into account, I have decided to dismantle the chassis and cabinet and keep only the specialist parts that I may need for my restored BT342.

Regards,

Dazzlevision
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Old 20th May 2015, 9:11 pm   #6
Colourstar
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Hi Dazzlevision

I wonder if you saw my recent thread on a BT336?

https://www.vintage-radio.net/forum/...d.php?t=116195

Like your set, my tube read decidedly down on a tester, but in actual use is perfectly watchable, albeit with the same rather smeary picture as yours! Other than that, interesting sets and rare survivors. I think your BT342 has more of a family resemblance to the original bow-fronts than my 336.

Steve
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Old 20th May 2015, 9:43 pm   #7
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Great result Dazzlevision. I saw an identical set outside a van at the NVCF before the main event opened. I remember telling Steve I saw a set similar to his own GEC in some respects. Same set I wonder?

Cheers
Brian
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Old 21st May 2015, 8:31 am   #8
dazzlevision
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Quote:
Originally Posted by Colourstar View Post
I wonder if you saw my recent thread on a BT336?
Hello Steve,

Yes, I did see your thread and I'm pleased to see that another example from this rather rare range of GEC sets has been preserved.

My restored BT342 does give a very good picture. One thing I would suggest it to replace the GEC made vision detector (GEXxx) diode with a Mullard type (e.g. OA70), as the GEC diode can produce some strange picture effects, but do test OK with a basic Ohms forward/reverse measurement.

I agree that the BT342 is more like its predecessors, whereas the other two sets in this range are of the more conventional "box" shape.

Regards,

Dazzlevision
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Old 24th May 2015, 4:14 am   #9
The teleman
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Hi Dave , nice to see you got it working , I never got round to doing anything with this set it had been in my to do pile for so long it had to go . I didn't know it had the wrong time base panel or the wrong lopt sorry about that .

Brian , it was the same set you spotted outside my van at the NVCF

Chris
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Old 24th May 2015, 8:28 am   #10
dazzlevision
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Hello Chris,

Not to worry about the incorrect timebase PCB and LOPT; you weren't to know. It will still yield plenty of chassis and cabinet set-specific parts to keep my restored and complete BT342 going.

I have since been working on the Sobell ST197-DS set you let me have and I hope to obtain a picture today or tomorrow (just reforming the two HT electrolytic "cans" at the moment). Luckily, I have a good LOPT for it. This will be documented in a new thread.

Regards,

Dazzlevision
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Old 24th May 2015, 9:44 am   #11
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

A very long production run for an obviously successful design. A descendant of my BT318. Well done.
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Old 24th May 2015, 11:59 am   #12
The teleman
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Default Re: The GEC BT342 television receiver, with VHF/FM radio facility.

Here is the transportable version the BT326. It uses the same chassis but laid out differently & a narrow crt is used
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