Centrum 850V ac mains transformer - UK Vintage Radio Repair and Restoration Discussion Forum

sapococas · 20th Dec 2007, 11:20 pm

Hello.

I am restoring an old radio. It is a Centrum 850V made in Sweden, but some parts are missing. My problem is with the AC mains transformer. This component is missing and I dont know the output voltage of the secondary

.This voltage is rectified by a 6X4 valve!

Does anyone know the correct voltage and current for this secondary? I only know about the 6.3V / 2.5A.

Here are 2 pictures to help identify this radio.

I would also like to know the date of production of this radio.

Best regards to all !!

newlite4 · 21st Dec 2007, 10:21 am

The heater winding requirement is as you say 6.3 volt feeding heaters in parallel. Regards the HT winding, select a mains transformer that has a 250V-0-250V secondary or thereabouts. Just select one that will fit neatly on the chassis, a set like this is unlikely to draw an large current from the transformer.
Neil

Ed_Dinning · 21st Dec 2007, 6:37 pm

Yes I would agree with Neil, it is likely to be 250-0-250, probabaly no more than 60mA rated (what type is the output valve?).
I would guess it is probabaly imeadiatley post war, say 1946-50.

Ed

sapococas · 21st Dec 2007, 8:41 pm

Thankyou , this information is most helpfull !The output valve is a "6V6G". With your help this old radio will come alive again!

Ed_Dinning · 22nd Dec 2007, 6:06 pm

The 6V6 is a standard valve for these sets (cheap and plentiful in the late 40's) and probably is not running near its max output so a 60mA transformer should be fine.
With a 6X4 there was often the temptation to run the rectifier from the main heater supply. If it's H-K insulation failed the results could be spectaular.
You may find a transformer with 2, 6.3 V windings. The one with the thinnest wire was for the rectifier, the other one for the rest of the valve heaters. These were quite common.

Ed

sapococas · 23rd Dec 2007, 12:09 am

I have all the information that i need to get the correct transformer for my radio!Thankyou and a mery christmas to all !

20th Dec 2007, 11:20 pm	#1
sapococas Retired Dormant Member Join Date: Dec 2007 Location: PORTUGAL, Palmela Posts: 3	Centrum 850V ac mains transformer Hello. I am restoring an old radio. It is a Centrum 850V made in Sweden, but some parts are missing. My problem is with the AC mains transformer. This component is missing and I dont know the output voltage of the secondary.This voltage is rectified by a 6X4 valve! Does anyone know the correct voltage and current for this secondary? I only know about the 6.3V / 2.5A. Here are 2 pictures to help identify this radio. I would also like to know the date of production of this radio. Best regards to all !! Attached Thumbnails

21st Dec 2007, 10:21 am	#2
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,805	Re: Centrum 850V ac mains transformer The heater winding requirement is as you say 6.3 volt feeding heaters in parallel. Regards the HT winding, select a mains transformer that has a 250V-0-250V secondary or thereabouts. Just select one that will fit neatly on the chassis, a set like this is unlikely to draw an large current from the transformer. Neil __________________ preserving the recent past, for the distant future.

21st Dec 2007, 6:37 pm	#3
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Centrum 850V ac mains transformer Yes I would agree with Neil, it is likely to be 250-0-250, probabaly no more than 60mA rated (what type is the output valve?). I would guess it is probabaly imeadiatley post war, say 1946-50. Ed

21st Dec 2007, 8:41 pm	#4
sapococas Retired Dormant Member Join Date: Dec 2007 Location: PORTUGAL, Palmela Posts: 3	Re: Centrum 850V ac mains transformer Thankyou , this information is most helpfull !The output valve is a "6V6G". With your help this old radio will come alive again!

22nd Dec 2007, 6:06 pm	#5
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Centrum 850V ac mains transformer The 6V6 is a standard valve for these sets (cheap and plentiful in the late 40's) and probably is not running near its max output so a 60mA transformer should be fine. With a 6X4 there was often the temptation to run the rectifier from the main heater supply. If it's H-K insulation failed the results could be spectaular. You may find a transformer with 2, 6.3 V windings. The one with the thinnest wire was for the rectifier, the other one for the rest of the valve heaters. These were quite common. Ed

23rd Dec 2007, 12:09 am	#6
sapococas Retired Dormant Member Join Date: Dec 2007 Location: PORTUGAL, Palmela Posts: 3	Re: Centrum 850V ac mains transformer I have all the information that i need to get the correct transformer for my radio!Thankyou and a mery christmas to all !