Philips 209U R18 - UK Vintage Radio Repair and Restoration Discussion Forum

See_Mos · 4th Nov 2019, 11:53 am

Hi All,

I have a Philips 209U with a damaged R18, the inrush resistor for the heater chain.

Does anyone know the cold and hot values or any ideas about a replacement please?

Obviously the set isn't worth much so cost could be an issue.

ms660 · 4th Nov 2019, 12:08 pm

5k cold, 160 ohms hot (approx.) according to the Trader sheet.

Check the thermistor data on the electrojumble site for the nearest specs if looking for a NOS or a good used replacement:

http://www.electrojumble.org/techdata.htm

Lawrence.

Herald1360 · 4th Nov 2019, 12:23 pm

Confusion for a while- there is no R18 in the Philips data. So.... Trader then.

R18 is likely a NTC thermistor of some sort- it's there to protect the scale lamp from switch on surge current through the heaters. The lamp is an odd 25V 100mA type. If you can't find any useful info on R18 (bear in mind unless it's open circuit, it can look pretty distressed and still be OK electrically) then I would suggest taking it out of the chain and fitting a value of R18 calculated to give the right heater current. The lamp could be fed from a dedicated series capacitor dropper straight across the mains or even its own small 24V transformer. If the lamp is a common size/shape you could use any voltage ~2.5W rated lamp with suitable supply arrangements.

See_Mos · 4th Nov 2019, 12:37 pm

Thanks Lawrence, I should have read the Trader sheet more carefully!

R18 is an NTC and it is broken in two so yes it's definitely faulty.

I have 120 and 240 volt MES lamps so another option would be to put the lamp across the heater chain to dim it down a bit and use a readily available NTC or even a fixed resistor to replace R18.

4th Nov 2019, 11:53 am	#1
See_Mos Hexode Join Date: Nov 2003 Location: Ossett, West Yorkshire, UK. Posts: 483	Philips 209U R18 Hi All, I have a Philips 209U with a damaged R18, the inrush resistor for the heater chain. Does anyone know the cold and hot values or any ideas about a replacement please? Obviously the set isn't worth much so cost could be an issue.

4th Nov 2019, 12:08 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Philips 209U R18 5k cold, 160 ohms hot (approx.) according to the Trader sheet. Check the thermistor data on the electrojumble site for the nearest specs if looking for a NOS or a good used replacement: http://www.electrojumble.org/techdata.htm Lawrence.

4th Nov 2019, 12:23 pm	#3
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Philips 209U R18 Confusion for a while- there is no R18 in the Philips data. So.... Trader then. R18 is likely a NTC thermistor of some sort- it's there to protect the scale lamp from switch on surge current through the heaters. The lamp is an odd 25V 100mA type. If you can't find any useful info on R18 (bear in mind unless it's open circuit, it can look pretty distressed and still be OK electrically) then I would suggest taking it out of the chain and fitting a value of R18 calculated to give the right heater current. The lamp could be fed from a dedicated series capacitor dropper straight across the mains or even its own small 24V transformer. If the lamp is a common size/shape you could use any voltage ~2.5W rated lamp with suitable supply arrangements. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

4th Nov 2019, 12:37 pm	#4
See_Mos Hexode Join Date: Nov 2003 Location: Ossett, West Yorkshire, UK. Posts: 483	Re: Philips 209U R18 Thanks Lawrence, I should have read the Trader sheet more carefully! R18 is an NTC and it is broken in two so yes it's definitely faulty. I have 120 and 240 volt MES lamps so another option would be to put the lamp across the heater chain to dim it down a bit and use a readily available NTC or even a fixed resistor to replace R18. Last edited by See_Mos; 4th Nov 2019 at 12:43 pm.