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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 12th Aug 2017, 9:19 pm   #21
matspar
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Default Re: And the next one! a GEC BT2147

Yes the 9" also has a flat faceplate David. Are these tubes meant to have an ion trap magnet? there isn't one fitted to mine.
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Old 12th Aug 2017, 9:29 pm   #22
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Default Re: And the next one! a GEC BT2147

Hi Matt,

Something wrong there. Has it had a turret tuner fitted (ITV modification)?

It seems that the first RF stage is mostly missing...
I used to have a spare brummie RF unit, I'm really not sur what bacame of it. It will probably be Christmas before I can have a good look for it. Maybe someone else has one to spare? Anyway, don't that stop you from continuing, you can still get the timebases working and check the tube.

Hi John,
I did have a go at a capacitor. This one had only faint markings on it unfortunately. I was surprised to find it actually had quite a strong cardbard tube hidden under all that treacle. It turned out to be one of the easier capacitors to restuff. You never know, I might end up putting them back in my set

Cheers
Andy
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Old 12th Aug 2017, 9:34 pm   #23
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Default Re: And the next one! a GEC BT2147

Hi Matt,
That's correct, no ion trap magnet on these tubes.

Cheers
Andy
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Old 12th Aug 2017, 9:43 pm   #24
matspar
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Default Re: And the next one! a GEC BT2147

Hi Andy,

That is weird! no sign or evidence of a turret tuner having ever been fitted. What on earth could have happened here then?!
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Old 12th Aug 2017, 9:48 pm   #25
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Default Re: And the next one! a GEC BT2147

Hmm,
Maybe the phantom bodger. There was a lot of it about.

It is worth having a look at top of the RF chassis to check if it has its full compliment of beehive trimmers. Anyway there seem to be tell tale marks where the aerial socket used to be...

Cheers
Andy
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Old 13th Aug 2017, 7:03 am   #26
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Default Re: And the next one! a GEC BT2147

The original TRF unit was replaced by an IF strip when ITA conversion took place. GEC supplied an external tuner together with a service exchange panel thus converting the receiver to a superhet.
They did not consider universal converters [Band 3 to Band 1 aerial converters] satisfactory. This made a very high quality and cheap conversion. I think GEC only charged around 2 for the exchange unit plus the cost of the tuner unit that was mounted in a Bakelite box. The original returned units would have been converted to an IF strip making the RF section [that was in the external converter] redundant.
This may well explain the removal of the RF amp in yours. The loose converter was probably lost some decades past. John.

Last edited by Heatercathodeshort; 13th Aug 2017 at 7:20 am. Reason: Added info.
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Old 13th Aug 2017, 8:23 am   #27
matspar
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Default Re: And the next one! a GEC BT2147

That would explain a lot John! may also explain the absence of the pair of N77's. Did this external tuner plug into the pair of valve bases by any chance? Think this is going to present a bit of a problem if I'm successful with the rest of the set
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Old 13th Aug 2017, 4:28 pm   #28
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Default Re: And the next one! a GEC BT2147

The standard GEC band 3 converter had two B7G adaptors that plugged into the RF position to gain power, heaters and H.T. and the second to feed the IF signal to the mixer now acting as an additional IF amp.

It's my guess that when GEC modified the RF plates, converting them to IF plates, they used a similar arrangement. This would have been very convenient as no modifications would have been needed to the heater ballast resistor.

I think the IF frequency is 34/38 mc/s so virtually any tuner from 1956 could be wired in. J.
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Old 14th Aug 2017, 4:14 pm   #29
MonochromeMarc
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Default Re: And the next one! a GEC BT2147

Quote:
Originally Posted by D Cassidy View Post
Hello DFWB.
I also was watching your thread 're the "green" cabinet, I'd like to have seen how you would have tackled that one.
The "Green" cabinet has now reappeared on another forum if you wish to follow it's rebuild.
https://www.radios-tv.co.uk/forum/bl...ation-project/
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