GEC BRT400 Receiver - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

PJL · 30th Aug 2023, 1:57 pm

What LT voltage are you getting?

Alf Fisher · 11th Sep 2023, 11:57 am

Hi PJL,
I'm getting about 6.1 on some and 6.2 on others but the transformer tag has 6.3 on it. I put this volt drop down to another GEC poor design feature of using such skinny single strand wire for the heater supplies. Its not much different to telephone extension wire! slightly thicker insulation.
I've reduced the LT current by 1.5 amps by removing the two KT81 valves (2 x 0.95A) and fitting a less sweaty 7B5 (0.4A) output valve.

The comment by turretslug is very valid - I think that for such a well respected organisation as GEC, the design of the power supply as a whole is poor. Come to think of it, I don't think these radios were ever meant to be repaired. There are some capacitors in very obscure and hidden places. C78 is one that is totally hidden underneath the long tagstrip and you would never see it unless you deliberately went searching for it. C91 is another buried one that's in the cathode circuit of the 2nd IF stage. There are two jammed in between the BFO coil and the chassis that are difficult to get out. These component references are as in the July 1952 manual which agrees with the components in the set I have. There were minor changes over the years and it was here that I found the difference between my radio and some on-line manuals that were different editions and not easy to read anyway.
A big thank you to Chris - onewatt for finding me an original manual.

Ian, I'm surprised to hear that out the ten or so BRT400s you had at Crowsley Park, you only had one smoker!

Alf

30th Aug 2023, 1:57 pm	#21
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,937	Re: GEC BRT400 Receiver What LT voltage are you getting?

11th Sep 2023, 11:57 am	#22
Alf Fisher Hexode Join Date: Sep 2005 Location: Potton, Bedfordshire, UK. Posts: 283	Re: GEC BRT400 Receiver Hi PJL, I'm getting about 6.1 on some and 6.2 on others but the transformer tag has 6.3 on it. I put this volt drop down to another GEC poor design feature of using such skinny single strand wire for the heater supplies. Its not much different to telephone extension wire! slightly thicker insulation. I've reduced the LT current by 1.5 amps by removing the two KT81 valves (2 x 0.95A) and fitting a less sweaty 7B5 (0.4A) output valve. The comment by turretslug is very valid - I think that for such a well respected organisation as GEC, the design of the power supply as a whole is poor. Come to think of it, I don't think these radios were ever meant to be repaired. There are some capacitors in very obscure and hidden places. C78 is one that is totally hidden underneath the long tagstrip and you would never see it unless you deliberately went searching for it. C91 is another buried one that's in the cathode circuit of the 2nd IF stage. There are two jammed in between the BFO coil and the chassis that are difficult to get out. These component references are as in the July 1952 manual which agrees with the components in the set I have. There were minor changes over the years and it was here that I found the difference between my radio and some on-line manuals that were different editions and not easy to read anyway. A big thank you to Chris - onewatt for finding me an original manual. Ian, I'm surprised to hear that out the ten or so BRT400s you had at Crowsley Park, you only had one smoker! Alf