Gec Bt302 - UK Vintage Radio Repair and Restoration Discussion Forum

System A · 25th Sep 2006, 8:59 pm

Hi everyone! Work started on my GEC BT 302 on Saturday. I took it over to Fernseh to start work on the restoration.

First of all, it was brought up on a Variac, when the voltage rose to 200v the mains filter blew. We snipped that out, then after 20 mins brought the voltage up to 230.

Line whistle started but the HT was only 140v. The HT finned rectifier was faulty. Fernseh had a Rediffusion pattern made part which consisted of a BY127, 127 Ohm, and a 0.1 micro UF cap.

After replacing this the HT rose to 210v. This produced a raster; still however no signal.
On investigation, the tuner had only channel 3 and 10 coils fitted as the set had come from Scotland. The coils on channel 3 had 2 extra turns of wire fitted, then we could tune in channel 1.

Here are the first pictures produced after that. More will follow when the restoration is complete.

Regards,
G.P.

FERNSEH · 25th Sep 2006, 10:53 pm

The GEC BT302 is one of my favourite TV sets. It was one of the first receivers in 1959 to take full advantage of the newly introduced 110 degree CRTs. The cabinet is truly slim and looks good.
More work has been done on the set. All the Hunts capacitors in the field timebase have been replaced, the result of that action is improved FTB performance although there was just enough height, A replacement PL84 solved that problem.
It was noticed that there had been some strange work carried out on the mains dropper resistor. Further examination showed that one of the HT supply sections had been by-passed and both heater and HT currents were flowing though one of the remaining HT sections. Having sorted that mess out the valve heaters have now got their correct voltage.
The 27 ohm resistor in the replacement HT rectifier assembly has been replaced by a 15 ohm component.

The tuner was supplied with only channel 3 and 10 coils. As Gary mentioned earlier an extra two turns were added to the oscillator coil to permit operation on Channel 1. This morning I added extra turns to the aerial and interstage coils.

The sound output was low, so many capacitors in the audio amplifier have been replaced to effect an improvement. Also the bias resistor of the N369/30P12 output valve was found to be reading 100 ohms. The correct value should be 270 ohms.
The set now delivers more than enough sound.

The original GEC branded CRT is bit dim, but it is improving with use.
The tube is a GEC 7405 = Mazda CME1703. 12.6 volt heater.

There is still work to done on this receiver. A number of Hunts capacitors in the vision AGC require replacement.

DFWB.

Heatercathodeshort · 26th Sep 2006, 8:47 pm

One of my favourites too DFWB. Easy to repair and reliable too. These sets were either loved or hated by the public due to the cabinets 'kidney' shape but sold well on the reconditioned market. Regards John.

System A · 5th Oct 2006, 8:56 pm

Hi everyone!

Here is the latest on my set. The tube is getting better as it's used. The set has not been used since 1966.
The mains dropper had been bodged by a previous repair. These are great looking sets, and are very slim for their time.

Regards

GP

25th Sep 2006, 8:59 pm	#1
System A Pentode Join Date: Feb 2006 Location: County Durham, UK. Posts: 234	Gec Bt302 Hi everyone! Work started on my GEC BT 302 on Saturday. I took it over to Fernseh to start work on the restoration. First of all, it was brought up on a Variac, when the voltage rose to 200v the mains filter blew. We snipped that out, then after 20 mins brought the voltage up to 230. Line whistle started but the HT was only 140v. The HT finned rectifier was faulty. Fernseh had a Rediffusion pattern made part which consisted of a BY127, 127 Ohm, and a 0.1 micro UF cap. After replacing this the HT rose to 210v. This produced a raster; still however no signal. On investigation, the tuner had only channel 3 and 10 coils fitted as the set had come from Scotland. The coils on channel 3 had 2 extra turns of wire fitted, then we could tune in channel 1. Here are the first pictures produced after that. More will follow when the restoration is complete. Regards, G.P. Attached Thumbnails

25th Sep 2006, 10:53 pm	#2
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Gec Bt 302 The GEC BT302 is one of my favourite TV sets. It was one of the first receivers in 1959 to take full advantage of the newly introduced 110 degree CRTs. The cabinet is truly slim and looks good. More work has been done on the set. All the Hunts capacitors in the field timebase have been replaced, the result of that action is improved FTB performance although there was just enough height, A replacement PL84 solved that problem. It was noticed that there had been some strange work carried out on the mains dropper resistor. Further examination showed that one of the HT supply sections had been by-passed and both heater and HT currents were flowing though one of the remaining HT sections. Having sorted that mess out the valve heaters have now got their correct voltage. The 27 ohm resistor in the replacement HT rectifier assembly has been replaced by a 15 ohm component. The tuner was supplied with only channel 3 and 10 coils. As Gary mentioned earlier an extra two turns were added to the oscillator coil to permit operation on Channel 1. This morning I added extra turns to the aerial and interstage coils. The sound output was low, so many capacitors in the audio amplifier have been replaced to effect an improvement. Also the bias resistor of the N369/30P12 output valve was found to be reading 100 ohms. The correct value should be 270 ohms. The set now delivers more than enough sound. The original GEC branded CRT is bit dim, but it is improving with use. The tube is a GEC 7405 = Mazda CME1703. 12.6 volt heater. There is still work to done on this receiver. A number of Hunts capacitors in the vision AGC require replacement. DFWB.

26th Sep 2006, 8:47 pm	#3
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Gec Bt 302 One of my favourites too DFWB. Easy to repair and reliable too. These sets were either loved or hated by the public due to the cabinets 'kidney' shape but sold well on the reconditioned market. Regards John.

5th Oct 2006, 8:56 pm	#4
System A Pentode Join Date: Feb 2006 Location: County Durham, UK. Posts: 234	Gec Bt 302 Hi everyone! Here is the latest on my set. The tube is getting better as it's used. The set has not been used since 1966. The mains dropper had been bodged by a previous repair. These are great looking sets, and are very slim for their time. Regards GP Attached Thumbnails