Ekco TVs with FM radio. - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 13th Nov 2013, 12:13 am

A common fault on certain Ekco and Ferranti TVs is a burn out of the FM/TV switch. Usually it's the HT switch. On TV operation all the valves are in use. When FM is selected the timebase valve heaters are switched out and a resistor is inserted into the heater chain. Lower down in the heater chain the CRT heater is switched out and a lamp to light up the fine tuning control is switched in instead.
On FM the HT supply to the timebase is removed and a 2.2K resistor is connected across the HT supply to maintain a similar load as the timebase valves. About 100mA.
So what does one do when the FM/TV fails? The part is almost impossible to find. I experienced this problem recently on a Ekco TC267/1. My solution was to remove the HT routing wires to the switch and rewire HT to the timebase on a permament basis. The same goes for the heaters of the timebase valves.
So now when the set is on FM radio the timebases are still running. The CRT heaters are switched off as before.
It's not a very green solution but neither is connecting a 2.2Kohm resistor across the HT supply. The truth is using a TV set as an FM radio receiver is not all that green anyway.

DFWB.

Heatercathodeshort · 13th Nov 2013, 9:10 am

A very common fault back in the 60's David. Customers very rarely used the FM section and I used to remove the offending wires from the burnt switch section and disable the operating lever from the trombone switch. It was a simple matter to connect the H.T. and heater connections for TV only operation. I must admit I'm not entirely happy with leaving the line timebase working during FM reception. OK if the LOPT is in 100% condition! John.

ntscuser · 13th Nov 2013, 5:36 pm

Quote:

Originally Posted by FERNSEH

My solution was to remove the HT routing wires to the switch and rewire HT to the timebase on a permament basis. The same goes for the heaters of the timebase valves.

I'm surprised Ekco didn't do it that way in the first place. Seems logical to me.

German Dalek · 13th Nov 2013, 6:51 pm

What do you think about a relay solution?
Switching higher currents with a relay will save the original switching contacts.
It has to be powered from a source where it makes no sense to run
the set with 12V DC or mains.
I shall keep this in mind, if I find the time to restore my Ekco.

Best regards,
German Dalek

mark pirate · 13th Nov 2013, 8:48 pm

I have an Ekco T310 with the offending switch, but it is working as it should with no sign of any damage or overheating.
Should it be treated like a system switch, I.E. power down the set before switching?

Mark

Heatercathodeshort · 13th Nov 2013, 9:05 pm

It's the Paxolin that breaks down Mark and I doubt if switching off would offer much protection. Not the best material for insulation between H.T. and A.C. heaters. It's only resin bonded compressed paper I believe. It used to go pop in the GEC BT300 I.F. plug and the tag strip supplying the mains dropper in the Thorn 850. On the whole it was very reliable and did sterling service in millions of radio applications. J.

13th Nov 2013, 12:13 am	#1
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Ekco TVs with FM radio. A common fault on certain Ekco and Ferranti TVs is a burn out of the FM/TV switch. Usually it's the HT switch. On TV operation all the valves are in use. When FM is selected the timebase valve heaters are switched out and a resistor is inserted into the heater chain. Lower down in the heater chain the CRT heater is switched out and a lamp to light up the fine tuning control is switched in instead. On FM the HT supply to the timebase is removed and a 2.2K resistor is connected across the HT supply to maintain a similar load as the timebase valves. About 100mA. So what does one do when the FM/TV fails? The part is almost impossible to find. I experienced this problem recently on a Ekco TC267/1. My solution was to remove the HT routing wires to the switch and rewire HT to the timebase on a permament basis. The same goes for the heaters of the timebase valves. So now when the set is on FM radio the timebases are still running. The CRT heaters are switched off as before. It's not a very green solution but neither is connecting a 2.2Kohm resistor across the HT supply. The truth is using a TV set as an FM radio receiver is not all that green anyway. DFWB. Attached Thumbnails

13th Nov 2013, 9:10 am	#2
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Ekco TVs with FM radio. A very common fault back in the 60's David. Customers very rarely used the FM section and I used to remove the offending wires from the burnt switch section and disable the operating lever from the trombone switch. It was a simple matter to connect the H.T. and heater connections for TV only operation. I must admit I'm not entirely happy with leaving the line timebase working during FM reception. OK if the LOPT is in 100% condition! John.

13th Nov 2013, 6:51 pm	#4
German Dalek Hexode Join Date: Jan 2011 Location: Düsseldorf, Germany. Posts: 368	Re: Ekco TVs with FM radio. What do you think about a relay solution? Switching higher currents with a relay will save the original switching contacts. It has to be powered from a source where it makes no sense to run the set with 12V DC or mains. I shall keep this in mind, if I find the time to restore my Ekco. Best regards, German Dalek __________________ And now something completly different: MARC BOLAN, he was/is the real king of Pop Music!

13th Nov 2013, 8:48 pm	#5
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Ekco TVs with FM radio. I have an Ekco T310 with the offending switch, but it is working as it should with no sign of any damage or overheating. Should it be treated like a system switch, I.E. power down the set before switching? Mark

13th Nov 2013, 9:05 pm	#6
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Ekco TVs with FM radio. It's the Paxolin that breaks down Mark and I doubt if switching off would offer much protection. Not the best material for insulation between H.T. and A.C. heaters. It's only resin bonded compressed paper I believe. It used to go pop in the GEC BT300 I.F. plug and the tag strip supplying the mains dropper in the Thorn 850. On the whole it was very reliable and did sterling service in millions of radio applications. J.