Red coloured getter in CRT - UK Vintage Radio Repair and Restoration Discussion Forum

high_vacuum_house · 14th Mar 2010, 12:18 am

Hello there,
Whilst having a look at my latest aqusition, a GEC BT1091 I noticed that the getter is rather red in colour and slightly transparent. I have not seen a getter that colour before. I presume as it is not silver in colour then it is likely suffering from gas. What make is the CRT and what would be a sittable replacement type.
Many thanks,
Christopher Capener

Skywave · 14th Mar 2010, 3:51 pm

Hi Chris,

Your CRT may not be faulty. If the getter used was a barium compound, it will leave a red deposit of the glass wall of the tube.

Al. / Skywave.

Heatercathodeshort · 14th Mar 2010, 7:48 pm

Two types of CRT were used in the BT1091. The most common type is a GEC 6504 with a strange 'pip' type EHT connector. A few Mullards were also fitted. As Skywave has said the getter need not be a hard 'mirror' and still give very good results. The 6504 is a 9" 'flat faced' triode and requires a higher focusing field than the Mullard tetrodes. Any 9" tube will fit providing you are willing to do a few mods such as maybe changing the base, fitting an ion trap, and arranging a mechanical fit. The 6504 has a 6.3v heater. The EHT potential is not critical and is given as 6.5kv in the GEC manual for the BT1091. Hope this helps? have you got as far as a picture yet? Regards, John.

Danny · 14th Mar 2010, 10:28 pm

These tube do go down to air sadly and i have at least four tubes that have suffered from this. but still worth trying it as you may be lucky. I bought a bt1091 at harpenden its getter is still silver so i have fingers crossed for this one. ferranti tubes work well as a replacement. but as stated above most 9" tubes can be used with simple mods. good luck. Danny

Heatercathodeshort · 15th Mar 2010, 9:53 am

Another problem with these GEC tubes is an intermittent or permanant O/C cathode connection within the tube. A sharp tap on the neck usually brings the picture back for a short period. It's a pity because these tubes are capable of giving a superb picture, very bright and contrasty, if you can find one....J.

14th Mar 2010, 12:18 am	#1
high_vacuum_house Octode Join Date: May 2003 Location: Belper Derbyshire Posts: 1,936	Red coloured getter in CRT Hello there, Whilst having a look at my latest aqusition, a GEC BT1091 I noticed that the getter is rather red in colour and slightly transparent. I have not seen a getter that colour before. I presume as it is not silver in colour then it is likely suffering from gas. What make is the CRT and what would be a sittable replacement type. Many thanks, Christopher Capener __________________ Interests in the collection and restoration of Tefifon players and 405 line television

14th Mar 2010, 3:51 pm	#2
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Red coloured getter in CRT Hi Chris, Your CRT may not be faulty. If the getter used was a barium compound, it will leave a red deposit of the glass wall of the tube. Al. / Skywave.

14th Mar 2010, 7:48 pm	#3
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Red coloured getter in CRT Two types of CRT were used in the BT1091. The most common type is a GEC 6504 with a strange 'pip' type EHT connector. A few Mullards were also fitted. As Skywave has said the getter need not be a hard 'mirror' and still give very good results. The 6504 is a 9" 'flat faced' triode and requires a higher focusing field than the Mullard tetrodes. Any 9" tube will fit providing you are willing to do a few mods such as maybe changing the base, fitting an ion trap, and arranging a mechanical fit. The 6504 has a 6.3v heater. The EHT potential is not critical and is given as 6.5kv in the GEC manual for the BT1091. Hope this helps? have you got as far as a picture yet? Regards, John.

14th Mar 2010, 10:28 pm	#4
Danny Heptode Join Date: Jul 2003 Location: North Walsham, Norfolk, UK. Posts: 516	Re: Red coloured getter in CRT These tube do go down to air sadly and i have at least four tubes that have suffered from this. but still worth trying it as you may be lucky. I bought a bt1091 at harpenden its getter is still silver so i have fingers crossed for this one. ferranti tubes work well as a replacement. but as stated above most 9" tubes can be used with simple mods. good luck. Danny

15th Mar 2010, 9:53 am	#5
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Red coloured getter in CRT Another problem with these GEC tubes is an intermittent or permanant O/C cathode connection within the tube. A sharp tap on the neck usually brings the picture back for a short period. It's a pity because these tubes are capable of giving a superb picture, very bright and contrasty, if you can find one....J.