Vidor CN 359 filter choke problem - UK Vintage Radio Repair and Restoration Discussion Forum

murphy512 · 6th Nov 2019, 2:25 pm

I am in the process of restoring a Vidor 329 and the filter choke (L13) is open and I was wondering if anybody can tell me the value of it and where I could get a replacement.
If I use resistor would that work or would it cause excessive hum?
Thanks
Aldo

Herald1360 · 6th Nov 2019, 2:53 pm

Anything around 10H at the current required (about 50mA) would be fine.

A 1K 5W resistor will likely work just fine. If hum's an issue, the smoothing cap (after the resistor) can be increased more or less ad lib, though reservoir cap for 5Z4G can only go up to 32uF max.

murphy512 · 8th Nov 2019, 10:33 am

Thank you for your suggestion.
I have used a 10w 470 ohms resistor as it gave the correct voltage.
A 22mf reservoir capacitor and 47 mf were used and the radio seems to work fine, no hum. The old ones (16 - 24 mf) were leaky anyway.
The radio is not very loud, but I am still working on it

murphy512 · 4th Dec 2019, 11:52 pm

After a complete recap and resistors checked, the radio is now working pretty well despite the voltages being about 15-20 volts less than specified on the schematic.
I do not have a spare rectifier, 5Z4G, to check if it makes any difference.
The EM34 was very dim, could just about be seen working on complete darkness, so I cheated and added a green led at the top of the valve and the effect is good enough. Checked the price for a new one and it is twice as much as what I paid for the radio.

cathoderay57 · 5th Dec 2019, 4:03 pm

Hi Aldo, nice work. I also recently restored a Vidor CN359 see here https://www.vintage-radio.net/forum/...d.php?t=158029 It had several faults including an o/c smoothing choke same as yours. Maybe the choke wasn't man enough for the job especially after HT capacitors started leaking & drawing extra current. I didn't ever manage to solve the intermittent "ploppy" reception on SW2 but otherwise it's a nice little performer. Cheers, Jerry

murphy512 · 5th Dec 2019, 11:43 pm

Thanks Jerry.
I have noticed that your set has a slight different tuning scale and the external speaker socket is also different as well as the knobs, maybe one is an export model?
I did not have any problems with any of the wavebands after a slight adjustment of C21 and C3
I also had a problem with the loudspeaker which sounded a bit screechy on certain frequencies. It was cured by spraying some servisol at the base of the speaker.
I have fitted a Bluetooth unit which is connected to the Gram socket and the sound is pretty good.
Regards
Aldo

Chris55000 · 6th Dec 2019, 12:21 am

Hi!

The primary of an old output transformer used on it's own makes a useful smoothing–choke and it might help you get h.t. close to the service sheet value, or, you could feed the anode of the output valve direct from the rectifier cathode (pin 8 of the 5Z4, h/k), and use the choke to feed the anodes and screen–grids of the first two (f.c./i.f ) valves, the anode of the a.f., and the screen grid of the output valve.

I realise you said the EM34 tuning–indicator is very dim, but it might be worth looking at it with the room lights switched off, (and that led out of the way!!) to see if it is responding to incoming signal in any way – in all probability, I suspect there's probably no movement of it either, which may point to low screen–grid voltages on either, or both, of the f.c. and i.f. stage valves!

If the indicator seems to make a lot of movement on faint signals, this points to too low h.t. line voltage, which would naturally make it dim to the point of being unusable!

Chris Williams

murphy512 · 7th Dec 2019, 12:33 am

Hi Chris,
thanks for your suggestions which I will try, I may have an old output transformer somewhere.

The EM34 was actually responsive, but you could just about see it working only on the outer edge of the valve in total darkness.
The voltages are 65v on pin 3, 214v on pin 5 and 42v on pin 6. Voltages on pin3 and 6 are higher than service sheet value and pin 4 of V1 and V2 are also higher than stated on service sheet.

6th Nov 2019, 2:25 pm	#1
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Vidor CN 359 filter choke problem I am in the process of restoring a Vidor 329 and the filter choke (L13) is open and I was wondering if anybody can tell me the value of it and where I could get a replacement. If I use resistor would that work or would it cause excessive hum? Thanks Aldo

6th Nov 2019, 2:53 pm	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,535	Re: Vidor CN 359 filter choke problem Anything around 10H at the current required (about 50mA) would be fine. A 1K 5W resistor will likely work just fine. If hum's an issue, the smoothing cap (after the resistor) can be increased more or less ad lib, though reservoir cap for 5Z4G can only go up to 32uF max. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

8th Nov 2019, 10:33 am	#3
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Re: Vidor CN 359 filter choke problem Thank you for your suggestion. I have used a 10w 470 ohms resistor as it gave the correct voltage. A 22mf reservoir capacitor and 47 mf were used and the radio seems to work fine, no hum. The old ones (16 - 24 mf) were leaky anyway. The radio is not very loud, but I am still working on it

4th Dec 2019, 11:52 pm	#4
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Re: Vidor CN 359 filter choke problem After a complete recap and resistors checked, the radio is now working pretty well despite the voltages being about 15-20 volts less than specified on the schematic. I do not have a spare rectifier, 5Z4G, to check if it makes any difference. The EM34 was very dim, could just about be seen working on complete darkness, so I cheated and added a green led at the top of the valve and the effect is good enough. Checked the price for a new one and it is twice as much as what I paid for the radio. Attached Thumbnails

5th Dec 2019, 4:03 pm	#5
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: Vidor CN 359 filter choke problem Hi Aldo, nice work. I also recently restored a Vidor CN359 see here https://www.vintage-radio.net/forum/...d.php?t=158029 It had several faults including an o/c smoothing choke same as yours. Maybe the choke wasn't man enough for the job especially after HT capacitors started leaking & drawing extra current. I didn't ever manage to solve the intermittent "ploppy" reception on SW2 but otherwise it's a nice little performer. Cheers, Jerry

5th Dec 2019, 11:43 pm	#6
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Re: Vidor CN 359 filter choke problem Thanks Jerry. I have noticed that your set has a slight different tuning scale and the external speaker socket is also different as well as the knobs, maybe one is an export model? I did not have any problems with any of the wavebands after a slight adjustment of C21 and C3 I also had a problem with the loudspeaker which sounded a bit screechy on certain frequencies. It was cured by spraying some servisol at the base of the speaker. I have fitted a Bluetooth unit which is connected to the Gram socket and the sound is pretty good. Regards Aldo Attached Thumbnails

6th Dec 2019, 12:21 am	#7
Chris55000 Nonode Join Date: Aug 2007 Location: Walsall Wood, Aldridge, Walsall, UK. Posts: 2,868	Re: Vidor CN 359 filter choke problem Hi! The primary of an old output transformer used on it's own makes a useful smoothing–choke and it might help you get h.t. close to the service sheet value, or, you could feed the anode of the output valve direct from the rectifier cathode (pin 8 of the 5Z4, h/k), and use the choke to feed the anodes and screen–grids of the first two (f.c./i.f ) valves, the anode of the a.f., and the screen grid of the output valve. I realise you said the EM34 tuning–indicator is very dim, but it might be worth looking at it with the room lights switched off, (and that led out of the way!!) to see if it is responding to incoming signal in any way – in all probability, I suspect there's probably no movement of it either, which may point to low screen–grid voltages on either, or both, of the f.c. and i.f. stage valves! If the indicator seems to make a lot of movement on faint signals, this points to too low h.t. line voltage, which would naturally make it dim to the point of being unusable! Chris Williams __________________ It's an enigma, that's what it is! This thing's not fixed because it doesn't want to be fixed!

7th Dec 2019, 12:33 am	#8
murphy512 Pentode Join Date: Mar 2008 Location: London, UK. Posts: 122	Re: Vidor CN 359 filter choke problem Hi Chris, thanks for your suggestions which I will try, I may have an old output transformer somewhere. The EM34 was actually responsive, but you could just about see it working only on the outer edge of the valve in total darkness. The voltages are 65v on pin 3, 214v on pin 5 and 42v on pin 6. Voltages on pin3 and 6 are higher than service sheet value and pin 4 of V1 and V2 are also higher than stated on service sheet.