Philips 206A working - UK Vintage Radio Repair and Restoration Discussion Forum

Malcolm G6ANZ · 31st Jan 2009, 6:06 pm

Success
A long post but I hope informative.
My first ‘restoration’ but more of a steep learning curve! I bought the Philips 206A and the seller said it was working and also included a spare case, and the trader sheet, the price was very reasonable.
Visual inspection showed nothing obviously wrong so I powered it up…..silence. Not even a hum. All valves lit and there was HT in the correct places. First fault was the volume control, when measured with a ohm meter it was o/c to the wiper across almost all its range. I took it apart and cleaned the track with IPA and lubricant. This made no difference as a close inspection showed the track to be totally absent. The mains switch is built on the front of the control so I had to rewire the mains to go to a rear mounted mains switch on a new pot. This brought back the audio stage.
Next fault. At this point the set worked quite well although slightly unstable and ‘not quite right’. Also there was an intermittent fault which cut the whole audio off. This was the screened lead to the IF valve grid from the IF transformer. By moving the lead the signal would come and go quite reliably. So.. out with the IF can and off with its case. Unsolder and remove the screened wire, which had indeed broken where it exited from the IF can, and replace it with a new length with some braid from a coax as the screening. This cured the intermittency and the set was working, but it still felt ‘wrong’
Measuring the HT it was a bit low and had more than the expected amount of ripple on it. This was traced back to the mains transformer. The 250-0-250 secondary was only producing voltage on one side. A rescue was considered using a silicon diode and resistor but this gave too much HT so was abandoned. I got hold of a scrap chassis via this forum and proceeded to remove the mains transformer and transplant it. Power up and main house trip blew. Not the RCD I had on the set. Odd I thought. Resistance measurements showed a leak from the primary to the earthy side of the heater winding. Hunt for good mains transformer. A shop on e-bay had a small NOS RS one 250-0-250, 6.3 and 5v secondaries. With the addition of a 1ohm resistor to drop the heater voltage for the rectifier valve it required 4v not 5v. Power up all ok. All three bands lively, no sign of instability.
Too good to last. Short wave stopped working. Long and medium fine. Out with the scope, Local oscillator not running on short wave but OK on medium and long. Resistance measurements around the wave change switch showed various contacts were either high resistance or open. Long think. I tried cleaning with IPA and contact lubricant but to no avail. It seemed that the ‘spring’ had gone from the switch elements. As I had a spare wave change switch and coils from the donated chassis I swopped them over. That’s easy to say but took several evenings work. Switch on, short wave ok medium wave ok long wave nothing. Back to the circuit. Checked the local oscillator running fine on all wavebands. I then checked the coils associated with long wave. L6 was open circuit. This is on a former with three other coils. Obvious answer is to swop over the working bank from the old switch bank. Another few evenings work and radio working on all three wavebands.
It still is not as sensitive as I think it should be but as all bands work and it looks good I think I’ll stop.
As I said at the start this is my first restoration and never thought it would be this difficult but it’s a good feeling when it all starts working.
Thanks to all on the forum, although I didn’t ask many questions there were answers from other problems which helped me solve mine.

The faulty coil L6 is at the top of the photo. Some of the hair thin wires can be seen.

Malcolm

Tim · 31st Jan 2009, 11:19 pm

Blimey, that set provided a few evenings of entertainment even before it was working!

Malcolm G6ANZ · 1st Feb 2009, 11:53 am

Thanks Tim, It did provide a few head scratching moments.The first photo attachment didnt work so here it is again.To make life a lot easier for the small delicate jobs i have now got an illuminated magnifier lamp.

Malcolm

31st Jan 2009, 6:06 pm	#1
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,042	Philips 206A working Success A long post but I hope informative. My first ‘restoration’ but more of a steep learning curve! I bought the Philips 206A and the seller said it was working and also included a spare case, and the trader sheet, the price was very reasonable. Visual inspection showed nothing obviously wrong so I powered it up…..silence. Not even a hum. All valves lit and there was HT in the correct places. First fault was the volume control, when measured with a ohm meter it was o/c to the wiper across almost all its range. I took it apart and cleaned the track with IPA and lubricant. This made no difference as a close inspection showed the track to be totally absent. The mains switch is built on the front of the control so I had to rewire the mains to go to a rear mounted mains switch on a new pot. This brought back the audio stage. Next fault. At this point the set worked quite well although slightly unstable and ‘not quite right’. Also there was an intermittent fault which cut the whole audio off. This was the screened lead to the IF valve grid from the IF transformer. By moving the lead the signal would come and go quite reliably. So.. out with the IF can and off with its case. Unsolder and remove the screened wire, which had indeed broken where it exited from the IF can, and replace it with a new length with some braid from a coax as the screening. This cured the intermittency and the set was working, but it still felt ‘wrong’ Measuring the HT it was a bit low and had more than the expected amount of ripple on it. This was traced back to the mains transformer. The 250-0-250 secondary was only producing voltage on one side. A rescue was considered using a silicon diode and resistor but this gave too much HT so was abandoned. I got hold of a scrap chassis via this forum and proceeded to remove the mains transformer and transplant it. Power up and main house trip blew. Not the RCD I had on the set. Odd I thought. Resistance measurements showed a leak from the primary to the earthy side of the heater winding. Hunt for good mains transformer. A shop on e-bay had a small NOS RS one 250-0-250, 6.3 and 5v secondaries. With the addition of a 1ohm resistor to drop the heater voltage for the rectifier valve it required 4v not 5v. Power up all ok. All three bands lively, no sign of instability. Too good to last. Short wave stopped working. Long and medium fine. Out with the scope, Local oscillator not running on short wave but OK on medium and long. Resistance measurements around the wave change switch showed various contacts were either high resistance or open. Long think. I tried cleaning with IPA and contact lubricant but to no avail. It seemed that the ‘spring’ had gone from the switch elements. As I had a spare wave change switch and coils from the donated chassis I swopped them over. That’s easy to say but took several evenings work. Switch on, short wave ok medium wave ok long wave nothing. Back to the circuit. Checked the local oscillator running fine on all wavebands. I then checked the coils associated with long wave. L6 was open circuit. This is on a former with three other coils. Obvious answer is to swop over the working bank from the old switch bank. Another few evenings work and radio working on all three wavebands. It still is not as sensitive as I think it should be but as all bands work and it looks good I think I’ll stop. As I said at the start this is my first restoration and never thought it would be this difficult but it’s a good feeling when it all starts working. Thanks to all on the forum, although I didn’t ask many questions there were answers from other problems which helped me solve mine. The faulty coil L6 is at the top of the photo. Some of the hair thin wires can be seen. Malcolm Attached Thumbnails

31st Jan 2009, 11:19 pm	#2
Tim Dekatron Join Date: Jan 2003 Location: Bradford on Avon, Wiltshire, UK. Posts: 3,310	Re: Philips 206A working Blimey, that set provided a few evenings of entertainment even before it was working! __________________ "Nothing is as dangerous as being too modern;one is apt to grow old fashioned quite suddenly."

1st Feb 2009, 11:53 am	#3
Malcolm G6ANZ Octode Join Date: Feb 2006 Location: Bristol, UK. Posts: 1,042	Re: Philips 206A working Thanks Tim, It did provide a few head scratching moments.The first photo attachment didnt work so here it is again.To make life a lot easier for the small delicate jobs i have now got an illuminated magnifier lamp. Malcolm Attached Thumbnails Last edited by Brian R Pateman; 1st Feb 2009 at 12:11 pm. Reason: Embedded image converted to thumbnail.