Bush TV1 rectifier query - UK Vintage Radio Repair and Restoration Discussion Forum

chipp1968 · 11th May 2008, 8:45 pm

I have a nicely working TV1, but wanted to fit a new rectifier valve. The valve fitted is a U52. The documents state a GZ32 or a UU8.

Sean Williams · 11th May 2008, 8:59 pm

Chipp,

The UU8 is a mazda octal, whereas the GZ32 is an International octal (as is the 5U4) - hence they are not interchangeable without a valve base change.

Personally I would leave the 5u4 in there - however, a GZ32 isnt that difficult to come by - try Colomor - they will have them in stock.

Cheers
Sean

mickjjo · 11th May 2008, 9:00 pm

The UU8 has a Mazda octal base and a 4 volt heater, The GZ32 has an international octal base and a 5 volt heater, so they are not interchangeable.....

Regards, Mick.

Heatercathodeshort · 13th May 2008, 7:36 am

H.T. rectifier valves were in short supply after the war and it is not unusual to discover various types and makes fitted as standard. The Pye D16T is a typical case either using a UU8 or GZ32 as original equipment. The U52 is an ideal replacement with a directly heated filament but this will make little difference as the valves warm very quickly in AC receivers. Service manuals show different part numbers for the mains transformers or tapped heater winding to suit the various valves employed. J.

chipp1968 · 15th May 2008, 6:22 pm

Just fitted a brand new GZ32. I really didn't think there would be any difference, the picture is definitely a little better, and the focus control actually works towards the centre of its movement, whereas it was right at the end of travel before, which means this also has improved.

Why should a new rectifier improve this out of interest?
The new valve is a lot smaller than the old one .

Heatercathodeshort · 15th May 2008, 7:15 pm

Hello Chipp,
The focus coil's strength is directly effected by the HT supply line voltage. If the HT was a little down the shunt adjustment pot would be a bit one ended. The supply to the eht section would also be slightly low resulting in reduced eht and this would effect the optimum focus setting. Hope this makes some sense. Regards, John.

11th May 2008, 8:45 pm	#1
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Bush TV1 rectifier query I have a nicely working TV1, but wanted to fit a new rectifier valve. The valve fitted is a U52. The documents state a GZ32 or a UU8.

11th May 2008, 8:59 pm	#2
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,517	Re: Bush TV1 rectifier query Chipp, The UU8 is a mazda octal, whereas the GZ32 is an International octal (as is the 5U4) - hence they are not interchangeable without a valve base change. Personally I would leave the 5u4 in there - however, a GZ32 isnt that difficult to come by - try Colomor - they will have them in stock. Cheers Sean __________________ Engineers make things work and have spare bits when finished

11th May 2008, 9:00 pm	#3
mickjjo Rest in Peace Join Date: Jul 2004 Location: Dartford, Kent, UK. Posts: 1,661	Re: Bush TV1 rectifier query The UU8 has a Mazda octal base and a 4 volt heater, The GZ32 has an international octal base and a 5 volt heater, so they are not interchangeable..... Regards, Mick.

13th May 2008, 7:36 am	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Bush TV1 rectifier query H.T. rectifier valves were in short supply after the war and it is not unusual to discover various types and makes fitted as standard. The Pye D16T is a typical case either using a UU8 or GZ32 as original equipment. The U52 is an ideal replacement with a directly heated filament but this will make little difference as the valves warm very quickly in AC receivers. Service manuals show different part numbers for the mains transformers or tapped heater winding to suit the various valves employed. J.

15th May 2008, 6:22 pm	#5
chipp1968 Rest in Peace Join Date: Jul 2006 Location: Somerset, UK. Posts: 2,356	Re: Bush TV1 rectifier query Just fitted a brand new GZ32. I really didn't think there would be any difference, the picture is definitely a little better, and the focus control actually works towards the centre of its movement, whereas it was right at the end of travel before, which means this also has improved. Why should a new rectifier improve this out of interest? The new valve is a lot smaller than the old one . Last edited by Mike Phelan; 30th Oct 2009 at 5:32 pm. Reason: Typos, FSB & FSK.

15th May 2008, 7:15 pm	#6
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Bush TV1 rectifier query Hello Chipp, The focus coil's strength is directly effected by the HT supply line voltage. If the HT was a little down the shunt adjustment pot would be a bit one ended. The supply to the eht section would also be slightly low resulting in reduced eht and this would effect the optimum focus setting. Hope this makes some sense. Regards, John.