Vidor CN359 Magic Eye Anomaly - UK Vintage Radio Repair and Restoration Discussion Forum

cathoderay57 · 14th Jul 2019, 10:53 am

Morning all, I am just finishing off resto of a Vidor CN359. The deflection on the EM34 was minimal but I fixed that by tweaking up the IF alignment 456kHz. The HT is a whisker too high at 250v whereas the Vidor service sheet specifies 242v. The HT choke was o/c which had a dc resistance of 390R and I have temporarily substituted a 350R ceramic resistor which probably explains this. All the other valve voltages measure close to those specified in the service sheet which does, however, mention that they are measured using an Avo Model 7 on 1000v range whereas I am using a Fluke 110 DVM so I would expect my measurements to be a shade higher. However, while the target of the EM34 magic eye reads 250v the anodes measure 85v and 52v whereas service data specifies 47v and 30v. The eye looks brand new and is 100% bright. Substituting another makes no difference. All of the relevant resistors including the 1M anode loads and the 680R cathode resistor are within tolerance. Should I be concerned, apart from the obvious issue that I do not want to shorten the life of the EM34 (although the set is only going to be used for an hour or two per week). I can only imagine I'd have to substitute higher value anode load resistors but thought I'd ask in case anybody has any ideas. Cheers, Jerry

ms660 · 14th Jul 2019, 11:00 am

The AVO 7 on the 1,000VDC range would be equal to a shunt resistor at the anodes of 500k.

The AVO 7 is a 500 Ohms per volt meter.

Lawrence.

Mike. Watterson · 14th Jul 2019, 11:22 am

Oddly magic eyes might last longer at higher voltages. The target connects direct to HT. The anodes (with resistors) have nothing to do with eye life. They only vary the deflector pin voltages. More negative grid means triodes go to off and deflector voltage rises. Increasing anode resistance gives larger shadows at no signal (AGC about -0.5V).

So nothing to worry about. If there is little AGC change, suspect any paper decoupling caps on the AGC as that will reduce the -ve signal (strong station) and prevent shadow vanishing.
The point of the EM34 is that the triodes and deflector design ensures the two shadows have different sensitivity.

The Anode resistors ONLY affect shadow size, never glow life.

space_charged · 14th Jul 2019, 3:38 pm

Magic eyes seemed to have a fairly short life suffering badly from loss of emission of the phosphor. The less often illuminated areas of the phosphor on the ones I have are still nice and bright. Not sure what the phosphor was in magic eyes. From the colour, copper doped zinc sulphide seems likely.

The anode voltage would govern the kinetic energy of the electrons, and of any ions generated from residual gas. A lower anode voltage on the phosphor might extend life at the expense of brightness. I doubt if it would be a big effect though.

Mike. Watterson · 14th Jul 2019, 4:52 pm

Quote:

Originally Posted by space_charged

The anode voltage would govern the kinetic energy of the electrons, and of any ions generated from residual gas. A lower anode voltage on the phosphor might extend life at the expense of brightness. I doubt if it would be a big effect though.

You'd imagine so, except the reverse may be true. However experiments with the few models with a separate grid (not the signal grid, but the CRT grid normally tied to the cathode) suggests that reducing the bias to have less current while increasing the target voltage results in longer life. Presumably because the electron collisions is what ages the phosphor, not the brightness per collision.

A quite blank one will light at 600V, i.e. a diode voltage doubler off main HT winding.

The later design devices use different phosphors, the glow on glass types are much bluer.
The DM70 / DM71 uses a different technique and phosphor, very like the modern VFD in set boxes, ovens, VCRs and amps. They fade very slowly.
The NOS Russian 6E5C (Cyrillic) or 6e5s in English/Roman is very like the old 6U5, it's not very bright when new and fades quite fast. The EM84 seems long lived (phosphor on glass). The EM80 and EM81 (and Russian/Chinese NOS equivalent) have an older phosphor and metal target, they don't last much better than the original 1930s eyes.

cathoderay57 · 14th Jul 2019, 9:33 pm

Thanks for the info - great thing about this Forum is you learn things all the time. Realignment did improve the deflection with the chassis on its side but then putting the chassis flat on the bench the deflection dropped off again. It wasn't loose IF tuning slugs and I could reproduce the fault tapping the base of the EM34. Cleaning and tightening the valve pin sockets didn't fix it but resoldering the EM34 pins seems to have done the trick. Cheers, Jerry

cathoderay57 · 14th Jul 2019, 9:47 pm

Having sorted out the magic eye I thought I was getting ahead of the game with the Vidor CN359. It's a nice compact set that produces a big sound. The trouble now is on Short Wave where the tuning seems sort of intermittent. I previously replaced the AGC decoupler. I will spray the earth contacts on the tuning cap rotors and see if that helps. I don't think it is shorting vanes as the problem doesn't appear on LW or MW . I did not replace the 0.1uF decouplers on the ECH35 or the EF39 cathodes but unless they have gone short circuit I wouldn't have expected those to cause this trouble. I will also check the padder capacitor at the bottom of the SW osc coil although tuning accuracy across the band seems good. I have cleaned wavechange switch contacts already. I have tried replacement valves with no effect. Any other ideas?

Mike. Watterson · 14th Jul 2019, 9:59 pm

Switch is most likely. I'd not go near the tuning cap if MW is OK.
Unlikely to be padder cap.

space_charged · 15th Jul 2019, 12:09 am

Quote:

Originally Posted by Mike. Watterson

Presumably because the electron collisions is what ages the phosphor, not the brightness per collision.

The perceived wisdom is that damage to the phosphor is caused by ions created by the electron beam, not electron bombardment. That might agree with the beam current versus particle energy explanation quite nicely. Ion creation is not so much dependant on electron energy as the number of electrons that hit residual gas molecules. So if you aim for higher electron energy but fewer electrons then fewer ions get created.

Might be something I could play with in my high vacuum chamber...

C

andrewferguson · 15th Jul 2019, 9:00 am

On a less related note, I've just finished replacing the capacitors to repair my CN359 (couldn't have done it without Mike's help). I haven't seen any more of these sets out "in the wild", care to share some photos?

cathoderay57 · 15th Jul 2019, 10:03 am

Here it is. Ser No 3014. The keen-eyed will see there is an elliptical speaker fitted which is not original. Although it works and sounds OK I have bought a 6-inch round Regentone speaker off eBay which should be a better fit. Also waiting for a replacement choke. You can see the temporary ceramic HT smoothing resistor in the below-chassis view bottom left next to the blue electrolytic. Cheers, Jerry

Mike. Watterson · 15th Jul 2019, 11:21 am

Excellent. Also doesn't have a "cost reduced" look as some of the battery sets in 1950s had.
Maybe designed by their Burndept Radio people who changed to producing commercial and military radios. Only the Vidor name and battery division was sold to Crompton when Cole retired. Curiously Ever Ready owned Burndept for a short while after Crompton bought Vidor.
Cole had been founder and owner and MD of Lissen and control bought by Ever Ready in 1928. In 1934 he setup Vidor to make batteries, buying Burndept Radio to do radios. Ever Ready wasn't amused and sacked him. It was to go to court but settled just before the case. Thus in mid 1930s the "new" Ever Ready models also often sold as Lissen too, and there were Vidor and Burndept models with the same chassis.
Ever Ready wound up the Lissen Brand/Company in 1945, though it's unlikely any were made after 1941 as both the Ever Ready / Lissen main radio factories were destroyed in the Blitz.
Vidor models are from 1934 to at least 1958. Some models may have been produced in 1959 which seems to be when radio production ended.
https://www.radiomuseum.org/m/vidor_gb_en_1~year.html

This got good reviews, both as a radio and for case design, though amazingly there is a valve version too.
https://www.radiomuseum.org/r/vidor_gem_cn440cn_44.html

Maybe the last model and no evidence it reached retail sales:
https://www.radiomuseum.org/r/vidor_viscount_cn443.html
or
https://www.radiomuseum.org/r/vidor_stowaway_cn447.html

I've always fancied the CN359 or a related model.

andrewferguson · 15th Jul 2019, 1:44 pm

Your model has different knobs to mine, I wonder which is the original? (You can see a picture of the knobs that mine has in the photo attached to this post).

You've done a very good job with all the wiring, I, ah, elected to leave the wiring that was in it as "if it ain't broke don't fix it". I assume you re-stuffed the wax capacitors?

I don't suppose you have a photo of the smoothing can capacitor? Mine had it's replaced by a RadioSpares part, and I'd be curious to see what the original was like.

cathoderay57 · 16th Jul 2019, 6:03 pm

First off many thanks to Mike for interesting info about Vidor and for the links. Andrew, hard to tell about the knobs. The photo at RM isn't clear enough to tell. The rubber sheathed wiring was too far gone to leave. Even the wires to the pilot lamps were flaked bare in places. Funny though the red wires seemed to survive OK while the blue green and yellow were badly perished. Maybe a different dye additive. New neoprene looks the part. I junked the old wax paper capacitors and replaced with yellow poly. The waxed low voltage electrolytics were left in situ for appearance's sake and modern miniature replacements wired in discreetly. Sorry, my main electrolytic isn't original but one from the spares box. The one fitted was a slim component with wires out each end and didn't look right. I'll post a pic later. Cheers,Jerry

cathoderay57 · 17th Jul 2019, 9:22 am

Andrew, the original main electrolytic would I think have looked very similar in appearance to the component you have got fitted. It would have been an aluminium can of value 16+24uF 350v wkg and probably manufactured by TCC (same maker as the low-voltage cathode caps). I don't think anyone makes capacitors of that exact combination of values in a single can anymore and anyway it doesn't matter; the closest you will get is a 16+32uF can which, if you are prepared to pay for it, will do the job nicely. Otherwise, as I think you have done, replacement with 2 axial capacitors underneath the chassis is just as good with a 16uF reservoir and a 22uF or 32uF smoother. Cheers, Jerry

kalee20 · 17th Jul 2019, 12:53 pm

Quote:

Originally Posted by space_charged

The perceived wisdom is that damage to the phosphor is caused by ions created by the electron beam, not electron bombardment. That might agree with the beam current versus particle energy explanation quite nicely. Ion creation is not so much dependant on electron energy as the number of electrons that hit residual gas molecules. So if you aim for higher electron energy but fewer electrons then fewer ions get created.

It would be nice to think you could improve magic eye life by using a high target voltage, and biasing it back to reduce current, thereby maintaining the same light emission. Unfortunately the grid of the display section, for every eye I have seen, is tied internally to the cathode (except DM70 which has no grid). The only control over what goes on in the display is by the control pin (internally connected to the triode anode and what creates the 'shadow'), and the target voltage.

So, raising the target voltage might improve light emission, but as this will draw more current, are we not in danger of raising the target temperature? I'm thinking, any improvement might be super-short lived.

Mike. Watterson · 17th Jul 2019, 1:13 pm

Indeed it's not possible on most magic eyes as they are internally 0V biased.
The keyhole on the DM70 is the grid. It's not actually using the same principle at all. Nor does it have huge fading issue. Different phosphor.
The DM70 / DM71 only works at all because it has a filamentary cathode and the filament is angled to the grid "mask" and anode.
https://www.radiomuseum.org/forum/dm70_operation.html#1

The DM160 or Russian iv-15 are purely VFD indicators, so while they have a filamentary cathode the entire anode is illuminated. They were designed to replace neons as annunciators as an ordinary Germanium transistor turns them on/off, though they can be dimmed.

The Russian 1E4A-B (rare) seems to be a copy of the DM70 concept. I have a couple, but the DM70 seems to work better.
https://www.radiomuseum.org/tubes/tube_1e4a-v.html

I have an Ekco that uses the o/p valve cathode voltage with a tap to power the DM70 filament. It's an AC/DC mains model. A Philips Colette looks like it uses the DM70 purely as a power indicator, actually it's the -1 gain amp for the Push Pull pair of DL96. It's strange as a 2nd DAF96 is a dedicated tone control, it could have been used. Indeed the Colette works with that as the -1 amp and the DM70 connected to AGC as a magic eye. It also needs the DK96 for gram and VHF, as the -ve grid voltage generated because of the local oscillator is filtered to bias the pair of DL96 to nearly class B.

Anyway, with almost all magic eyes, the only point of using a voltage doubler (500V HT) is when otherwise it's dead anyway. I experimented, a dead one will light. However I put in a NOS Russian eye and left the HT as per original, not a big deal with single shadow tubes, but a shame for the dual sensitivity dual shadow EM34 or the cute TV4.

I've also made a replica using a load of green LEDs and a bargraph IC. Power it from the heater voltage. Someone made one with spinning disc.

14th Jul 2019, 11:00 am	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Vidor CN359 Magic Eye Anomaly The AVO 7 on the 1,000VDC range would be equal to a shunt resistor at the anodes of 500k. The AVO 7 is a 500 Ohms per volt meter. Lawrence. Last edited by ms660; 14th Jul 2019 at 11:05 am.

14th Jul 2019, 11:22 am	#3
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Vidor CN359 Magic Eye Anomaly Oddly magic eyes might last longer at higher voltages. The target connects direct to HT. The anodes (with resistors) have nothing to do with eye life. They only vary the deflector pin voltages. More negative grid means triodes go to off and deflector voltage rises. Increasing anode resistance gives larger shadows at no signal (AGC about -0.5V). So nothing to worry about. If there is little AGC change, suspect any paper decoupling caps on the AGC as that will reduce the -ve signal (strong station) and prevent shadow vanishing. The point of the EM34 is that the triodes and deflector design ensures the two shadows have different sensitivity. The Anode resistors ONLY affect shadow size, never glow life.

14th Jul 2019, 3:38 pm	#4
space_charged Hexode Join Date: Dec 2014 Location: West Midlands, UK. Posts: 315	Re: Vidor CN359 Magic Eye Anomaly Magic eyes seemed to have a fairly short life suffering badly from loss of emission of the phosphor. The less often illuminated areas of the phosphor on the ones I have are still nice and bright. Not sure what the phosphor was in magic eyes. From the colour, copper doped zinc sulphide seems likely. The anode voltage would govern the kinetic energy of the electrons, and of any ions generated from residual gas. A lower anode voltage on the phosphor might extend life at the expense of brightness. I doubt if it would be a big effect though.

14th Jul 2019, 9:33 pm	#6
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,382	Re: Vidor CN359 Magic Eye Anomaly Thanks for the info - great thing about this Forum is you learn things all the time. Realignment did improve the deflection with the chassis on its side but then putting the chassis flat on the bench the deflection dropped off again. It wasn't loose IF tuning slugs and I could reproduce the fault tapping the base of the EM34. Cleaning and tightening the valve pin sockets didn't fix it but resoldering the EM34 pins seems to have done the trick. Cheers, Jerry

14th Jul 2019, 9:47 pm	#7
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,382	Vidor CN359 more issues Having sorted out the magic eye I thought I was getting ahead of the game with the Vidor CN359. It's a nice compact set that produces a big sound. The trouble now is on Short Wave where the tuning seems sort of intermittent. I previously replaced the AGC decoupler. I will spray the earth contacts on the tuning cap rotors and see if that helps. I don't think it is shorting vanes as the problem doesn't appear on LW or MW . I did not replace the 0.1uF decouplers on the ECH35 or the EF39 cathodes but unless they have gone short circuit I wouldn't have expected those to cause this trouble. I will also check the padder capacitor at the bottom of the SW osc coil although tuning accuracy across the band seems good. I have cleaned wavechange switch contacts already. I have tried replacement valves with no effect. Any other ideas?

14th Jul 2019, 9:59 pm	#8
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Vidor CN359 more issues Switch is most likely. I'd not go near the tuning cap if MW is OK. Unlikely to be padder cap.

15th Jul 2019, 9:00 am	#10
andrewferguson Hexode Join Date: Aug 2016 Location: Edinburgh, Scotland, UK. Posts: 262	Re: Vidor CN359 more issues On a less related note, I've just finished replacing the capacitors to repair my CN359 (couldn't have done it without Mike's help). I haven't seen any more of these sets out "in the wild", care to share some photos?

15th Jul 2019, 10:03 am	#11
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,382	Re: Vidor CN359 more issues Here it is. Ser No 3014. The keen-eyed will see there is an elliptical speaker fitted which is not original. Although it works and sounds OK I have bought a 6-inch round Regentone speaker off eBay which should be a better fit. Also waiting for a replacement choke. You can see the temporary ceramic HT smoothing resistor in the below-chassis view bottom left next to the blue electrolytic. Cheers, Jerry Attached Thumbnails

15th Jul 2019, 11:21 am	#12
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Vidor CN359 Magic Eye Anomaly Excellent. Also doesn't have a "cost reduced" look as some of the battery sets in 1950s had. Maybe designed by their Burndept Radio people who changed to producing commercial and military radios. Only the Vidor name and battery division was sold to Crompton when Cole retired. Curiously Ever Ready owned Burndept for a short while after Crompton bought Vidor. Cole had been founder and owner and MD of Lissen and control bought by Ever Ready in 1928. In 1934 he setup Vidor to make batteries, buying Burndept Radio to do radios. Ever Ready wasn't amused and sacked him. It was to go to court but settled just before the case. Thus in mid 1930s the "new" Ever Ready models also often sold as Lissen too, and there were Vidor and Burndept models with the same chassis. Ever Ready wound up the Lissen Brand/Company in 1945, though it's unlikely any were made after 1941 as both the Ever Ready / Lissen main radio factories were destroyed in the Blitz. Vidor models are from 1934 to at least 1958. Some models may have been produced in 1959 which seems to be when radio production ended. https://www.radiomuseum.org/m/vidor_gb_en_1~year.html This got good reviews, both as a radio and for case design, though amazingly there is a valve version too. https://www.radiomuseum.org/r/vidor_gem_cn440cn_44.html Maybe the last model and no evidence it reached retail sales: https://www.radiomuseum.org/r/vidor_viscount_cn443.html or https://www.radiomuseum.org/r/vidor_stowaway_cn447.html I've always fancied the CN359 or a related model. Last edited by Mike. Watterson; 15th Jul 2019 at 11:35 am.

15th Jul 2019, 1:44 pm	#13
andrewferguson Hexode Join Date: Aug 2016 Location: Edinburgh, Scotland, UK. Posts: 262	Re: Vidor CN359 Magic Eye Anomaly Your model has different knobs to mine, I wonder which is the original? (You can see a picture of the knobs that mine has in the photo attached to this post). You've done a very good job with all the wiring, I, ah, elected to leave the wiring that was in it as "if it ain't broke don't fix it". I assume you re-stuffed the wax capacitors? I don't suppose you have a photo of the smoothing can capacitor? Mine had it's replaced by a RadioSpares part, and I'd be curious to see what the original was like.

16th Jul 2019, 6:03 pm	#14
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,382	Re: Vidor CN359 Magic Eye Anomaly First off many thanks to Mike for interesting info about Vidor and for the links. Andrew, hard to tell about the knobs. The photo at RM isn't clear enough to tell. The rubber sheathed wiring was too far gone to leave. Even the wires to the pilot lamps were flaked bare in places. Funny though the red wires seemed to survive OK while the blue green and yellow were badly perished. Maybe a different dye additive. New neoprene looks the part. I junked the old wax paper capacitors and replaced with yellow poly. The waxed low voltage electrolytics were left in situ for appearance's sake and modern miniature replacements wired in discreetly. Sorry, my main electrolytic isn't original but one from the spares box. The one fitted was a slim component with wires out each end and didn't look right. I'll post a pic later. Cheers,Jerry

17th Jul 2019, 9:22 am	#15
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,382	Re: Vidor CN359 Magic Eye Anomaly Andrew, the original main electrolytic would I think have looked very similar in appearance to the component you have got fitted. It would have been an aluminium can of value 16+24uF 350v wkg and probably manufactured by TCC (same maker as the low-voltage cathode caps). I don't think anyone makes capacitors of that exact combination of values in a single can anymore and anyway it doesn't matter; the closest you will get is a 16+32uF can which, if you are prepared to pay for it, will do the job nicely. Otherwise, as I think you have done, replacement with 2 axial capacitors underneath the chassis is just as good with a 16uF reservoir and a 22uF or 32uF smoother. Cheers, Jerry

17th Jul 2019, 1:13 pm	#17
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Vidor CN359 Magic Eye Anomaly Indeed it's not possible on most magic eyes as they are internally 0V biased. The keyhole on the DM70 is the grid. It's not actually using the same principle at all. Nor does it have huge fading issue. Different phosphor. The DM70 / DM71 only works at all because it has a filamentary cathode and the filament is angled to the grid "mask" and anode. https://www.radiomuseum.org/forum/dm70_operation.html#1 The DM160 or Russian iv-15 are purely VFD indicators, so while they have a filamentary cathode the entire anode is illuminated. They were designed to replace neons as annunciators as an ordinary Germanium transistor turns them on/off, though they can be dimmed. The Russian 1E4A-B (rare) seems to be a copy of the DM70 concept. I have a couple, but the DM70 seems to work better. https://www.radiomuseum.org/tubes/tube_1e4a-v.html I have an Ekco that uses the o/p valve cathode voltage with a tap to power the DM70 filament. It's an AC/DC mains model. A Philips Colette looks like it uses the DM70 purely as a power indicator, actually it's the -1 gain amp for the Push Pull pair of DL96. It's strange as a 2nd DAF96 is a dedicated tone control, it could have been used. Indeed the Colette works with that as the -1 amp and the DM70 connected to AGC as a magic eye. It also needs the DK96 for gram and VHF, as the -ve grid voltage generated because of the local oscillator is filtered to bias the pair of DL96 to nearly class B. Anyway, with almost all magic eyes, the only point of using a voltage doubler (500V HT) is when otherwise it's dead anyway. I experimented, a dead one will light. However I put in a NOS Russian eye and left the HT as per original, not a big deal with single shadow tubes, but a shame for the dual sensitivity dual shadow EM34 or the cute TV4. I've also made a replica using a load of green LEDs and a bargraph IC. Power it from the heater voltage. Someone made one with spinning disc.