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Vidor 396A - 1952

Domestic Valve & Transistor receivers, Radiograms, Gramophones, Amplifiers, Hi-fi, Speakers, Record players, Music centres, Tape machines, Cassette players & Jukeboxes
 
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Vidor 396A - 1952

Post by Sparks » Tue May 10, 2016 12:59 pm

Vidor outside (Medium).JPG
Outside
VIDOR 396A
Picked this up on a car boot sale this morning. Dated at May, 1952, by date on a capacitor. Looks like it has had a lot of use judging by the wear around the control knobs.
The transformer looks like it has been "fried!" A few dodgy looking caps spotted, and much perished wiring. All valve filaments test OK! Main components, Variable capacitor, IF cans, loudspeaker look to be in good shiny condition.
Bob
Attachments
Vidor inside (Medium).JPG
Inside

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Tue May 10, 2016 7:04 pm

I have one of these. Unusually it's isolated, as you noticed. More unusual is that it has valve rectifier, which last better than selenium.
The wiring was all perished.
All the waxy caps faulty (cause burn out of audio transformer, o/p valve etc as most here know.). The Electrolytic cap reformed well.
I put a 3 core flex and earthed metal work.
I made replica working vidor battery packs and resprayed metal panel.

The restore might be on here somewhere?
Image
A load of them here:
http://www.radiomuseum.org/r/vidor_atta ... _396a.html
The early non-"A" version may be different bias and tended to use tubes imported from USA. It also has one less adjustment (2 rather than 3) for mains voltage.

The DL94 (=3V4) is about twice output of DL91/DL92 or later DL96, so "big" sets continued to use DL94 up to 1958.

Restoration is more like working with a meccanno set than electronics. Carefully note where wires on PSU chassis go on radio chassis.

It works well.

 
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Re: Vidor 396A - 1952

Post by Sparks » Tue May 10, 2016 7:18 pm

It was a job to get the chassis out. Found on internet advice to unsrew the feet on bottom of set either side of tuning dial. One was missing, and the other was exceeding stiff. Eventually grabbed it with mole grips and used brute force. When it came away, it was clear that it was not a screw at all, but had been knocked in with three prongs. Then removed the third one with the mole grips to find it was the same. The fourth, and last, was the screw! :ccb Chassis then came out easy enough. I doubt if I will restore it properly. Most likely take out all the mains section, rewire the filaments in parallel and get it going as battery only.
Bob

 
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Re: Vidor 396A - 1952

Post by Rebel Rafter » Tue May 10, 2016 7:37 pm

Hi from RR. That looks a bit similar to the Pye jewel case set mains version. I've got a battery only version and my o/p transformer primary was also o/c but I managed to make one from a transformer from an old nokia phone charger, see my post on that elsewhere. I also recently found the battery/mains version of the Pye set on a flea market somewhere and I decided how much I was prepared to pay for it and then I asked the lad who was selling it but he said he had to ring his mum for a price and she apparently wasn't answering so I couldn't wait all day for it so I didn't get it. What a stinker. RR.

 
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Re: Vidor 396A - 1952

Post by Sparks » Tue May 10, 2016 9:17 pm

I had my eye on this one for three weeks. It started at £20. The 2nd week he had gone down to £15, and today he went down to £10. I felt it would have been pushing my luck to wait another week, as there are a number of vintage radio types prowling about the market (Preston). There was also a huge box of 1960s Practical Wireless, must have been a couple of hundred, but I passed them up - no storage space!
Bob

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Tue May 10, 2016 9:53 pm

Sparks wrote:It was a job to get the chassis out. Found on internet advice to unsrew the feet on bottom of set either side of tuning dial. One was missing, and the other was exceeding stiff. Eventually grabbed it with mole grips and used brute force. When it came away, it was clear that it was not a screw at all, but had been knocked in with three prongs. Then removed the third one with the mole grips to find it was the same. The fourth, and last, was the screw! :ccb Chassis then came out easy enough. I doubt if I will restore it properly. Most likely take out all the mains section, rewire the filaments in parallel and get it going as battery only.
Bob

I forgot about the feet. I should have mentioned that.

A shame not to restore it properly. Also bias on output valve is due to the series filament. A parallel LT set wastes about 5V of HT in a series resistor in LT.

The mains unit is pretty easy to restore. In the unlikely event the transformer is really banjacked you can use a shaver transformer and 2 x 1N4007.

 
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Re: Vidor 396A - 1952

Post by hamid_1 » Tue May 10, 2016 10:09 pm

Sparks wrote:... I doubt if I will restore it properly. Most likely take out all the mains section, rewire the filaments in parallel and get it going as battery only.
Bob


No need to rewire the filaments to use it on batteries. It was designed for 7.5v + 90v battery pack, no longer available but easy and cheap to make.

For the 7.5v battery, try this:
http://www.componentshop.co.uk/battery-holder-for-5-aa-batteries-side-by-side-with-solder-tags.html

5xAA battery holder, only 50p plus postage. Other suppliers are available.

For the 90v battery, you could connect ten PP3 batteries together with some clips like these: http://www.componentshop.co.uk/pp3-standard-lead.html

AA and PP3 9v batteries are available at your local "Pound Shop". It should be possible to build a 7.5v + 90v battery pack for less than £10 altogether. But don't condemn the mains transformer just yet. Some of them do have lumps of wax stuck to them, like yours, yet they still work. If you are worried, you can unplug the valves and test the transformer off-load, observing if it starts getting hot (shorted turns).

Actually it was rather good of Vidor to include an isolating mains transformer in this radio. I have several of these little battery valve portables, including two Marconiphone ones which just have dropper resistors across the mains - and a potentially live chassis. The first mains/battery one I acquired from a car boot sale in 2009 - a Vidor "Lady Anne" - had an isolating transformer too. I restored it simply by replacing the wax paper capacitors and used it on the mains without any problem. I'm pretty sure I have another Vidor set like yours, but haven't got round to restoring it yet ... must have a look at it sometime :qq1

 
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Re: Vidor 396A - 1952

Post by Cathovisor » Tue May 10, 2016 10:37 pm

For some reason Vidor were very 'hot' on isolated chassis; even their early TV sets were the same and in fact they made a big deal of that in their sales literature.

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Wed May 11, 2016 9:13 am

I was thinking, the HT is the more awkward bit, 10 off PP3 in a replica box.
More work to change filaments to parallel than fix PSU! You'd have to change LT plug.
Besides 5 off Alkaline AA for the LT is about same life as original five Zinc Carbon "B" sized cells and best value batteries to buy. The 50mA rather than 250mA also means less series resistance losses in plug and batteries.

By all means don't bother fixing PSU if you find it too difficult, but changing the filament wiring is waste of time and energy.

 
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Re: Vidor 396A - 1952

Post by Sparks » Thu May 12, 2016 8:21 am

It certainly wouldn't be too difficult to fix the PSU, but I don't like the "mains" versions of these sets. As for "hard" that is what I am looking for. No fun in "easy!" :)
When I see old radios on car boot sales, I go for the most decrepit and battered looking ones simply for the pleasure of getting them going again! If the seller comes out with "Its in perfect working condition," I don't even bother buying it!
I have the circuit of this one in my Radio & TV Servicing books, so no big problem.
Generally, I am not interested in restoring back to new condition, just getting them working well is good enough for me. The only one I ever really restored was an R1155.
Bob

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Thu May 12, 2016 12:16 pm

Sparks wrote:It certainly wouldn't be too difficult to fix the PSU, but I don't like the "mains" versions of these sets.

This one is isolated.

It's AC/DC live chassis ones with metal panel (Marconiphone/HMV etc!) that are "exciting": "Take care when re-assembling to refit the insulating washers and in correct orientation or the front panel may be live."
The USA models only have a wax cap between reversible line cord and metal chassis and often metal case. You don't want a dropper or autotransformer to adapt them from 115V to 220-240V.

If it's USA battery/mains I use shaver outlet in box with trailing lead.

For UK Battery/Mains models I use same box design, except it has an extra hole drilled for earth pin of a 3 pin 5 amp plug. I have 5amp 3 pin plug on most dubious Battery / Mains 220-240V set, with neutral to "chassis" side. Only very "safe" design Battery/Mains have original Europlug or UK modern 3 pin plug.

I have three shaver outlets mounted in boxes with trailing leads. I found I needed to add 2n2F 1KV ceramic XY caps between earth and the two sides of centre tapped 230V otherwise there was a buzz. The earth doesn't connect to the secondary of shaver transformer as that would make it LESS safe, as the two pin 115V or 230V plugs could be either way round.

The shaver transformers often have a gap in core to limit power and/or a thermistor in series as to met spec they must provide isolation and power limiting.

I have a Philips, German and Pye battery / mains models with decent isolated transformers and cases. They have either UK 3 pin plug or the original "Europlug". I do isolation leakage tests.

 
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Re: Vidor 396A - 1952

Post by Sparks » Thu May 12, 2016 2:03 pm

I know it is, but it may not be isolated well enough if the "fried" transformer is on the points of insulation failure. But I still prefer battery sets these days. Not because I am afraid of high voltages (worked for over 32 years with marine radar, transmitters etc with hundreds or thousands of Volts)! I don't like mains sets because from time to time I write articles, and I prefer to use HT of 45 to 90 Volts obtained from batteries for the safety of my readers, not my safety! :qq1
When I was at school in the 50s, no-one seemed to bother much about 11-year-olds messing with mains radios, but rather different now! :ccf
Bob

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Thu May 12, 2016 2:53 pm

That's why mine has a 3 core flex, which is earthed. Just in case. The transformer doesn't look at all fried.

I think it now has a 5A round three pin plug for shaver adaptor, just checked, it does. The regular UK plug takes too much space

From memory, I think the transformer has a shield connection between primary and secondary. You could even replace the transformer with a shaver one, though then you'd lose the 6.3V AC for the rectifier valve. It's split design, with screen connection thus if it's cooked it burns out, it won't short output to mains if you earth the shield.

However feel free to disconnect PSU and use it on 5 x AA and 10 x PP3. Performance is good due to ample size loop aerials and decent IFTs.

90V DC via batteries can be quite fatal.

 
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Re: Vidor 396A - 1952

Post by Sparks » Thu May 12, 2016 3:26 pm

It certainly looks "fried" to me though! There is no need to use 10 PP3 batteries on sets like this - they will work on 45 Volts!
I must have been lucky with 90 Volt batteries (or thick skinned), never had a shock off one that I can recall. :ccg But you would know about it if you stuck your tongue on one! :elc: :aaj
Bob

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Thu May 12, 2016 5:36 pm

Sparks wrote: There is no need to use 10 PP3 batteries on sets like this - they will work on 45 Volts!

Very badly! 54V is the lowest HT they are designed for (EOL 0.9V per cell) and they are poor below 65V. There are sets designed to work off 45V (30V end point) and 67V (42V end point). The resistors and bias is different. You won't use more than about 1/2 capacity of 5 x PP3 before it stops working. False economy!

You don't need 90V if using paralleled stacks of Lithium coin cells (78V will do) as they have a higher end point. You do need parallel stacks (via diodes and also safety, pico fuses) as the coin cells are quite high impedance, limited current.

The USA and Japan made pocket sets with just one B7G valve for audio out and either hearing aid or military wire ended sub-miniature tubes using 1 D cell for LT and either a long skinny 45V or 67V pack with a PP3 style top.

If a set isn't going to be used properly, then IMO it might as well be a display item. That's why I've made replica packs duplicating original voltage and life, where possible.
http://www.radiomuseum.org/collection/m ... erson.html

It's also why I use the USA battery/mains with external 115V isolated supply as well as making the battery packs. The Zenith Transoceanic I have has not just the original style and capacity main battery, but the 1.5V hearing aid LT pack that's used for the scale lamp. The socket is used with half turn to undo top and then it has an alkaline C cell inside to give only a little more than original capacity.

 
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Re: Vidor 396A - 1952

Post by Sparks » Thu May 12, 2016 6:48 pm

Mine work well enough on 45 Volts! Absolutely no point in making it display only. I don't know anyone around here who is the slightest bit interested in such things! :ccf I am not a member of a radio club, because I don't play around with radios all the time. I can go for weeks or months without touching them But my interest will revive by finding one on the local giant car boot sale that now runs for six days a week. :aad This afternoon I started a progressive 3-valve TRF. I had been fitting the vintage components on the board for over a week now. Wired up the detector today and it works fine. RF chokes for coils that I will no doubt be told are not up to much. But even I am surprised by the performance with only one valve in it. Valves will be SG215 (RF) HL2 (Dectector) and KT2 Output. Running on 100 Volts HT and 2V sealed lead acid LT.
Bob

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Thu May 12, 2016 7:03 pm

Here is the earlier thread of complete restore of Vidor CN396A about five years ago.
viewtopic.php?f=3&t=902

At that stage I'd done 45 years of Radio, TV, Electronics etc, but only a few vintage restores.
It's total nonsense to operate 90V HT (really minimum 55V to 60V HT) sets on 45V battery, costs just as much and performance is abysmal. No 90V set I have works sensibly at 45V. I have plenty of them! Twenty of them here in library. More elsewhere. My Bench PSU does 45V, it would be handy if they did work at 45V.

If you think people aren't safe with 90V HT, then give them 1.5V to 12V transistor sets.

Image


Image

Image

[Circuit diagram confirms my five year old memory that the transformer DOES have a screen betweeen primary and secondary]

The "real" load is somewhat below 140 Ohms due to the resistors to balance the "cathode" currents etc, but will vary with HT current.

Image


The LT voltage for "7.5V" series filament from a PSU should be 6.5V. However 6.6V to 6.7V is close enough. [Recommended limit is 6.8V for mains PSUs] The HT is only a nominal 90V (About 100V to 95V with fresh cells down to 60V [or 55V] when exhausted), 72V to 103V is fine [on mains.]

I then re-mounted the PSU (where did I put the screws in April?) on the main chassis after soldering the 3 wires to switch (mains in to transformer, HT out and LT out). The 0V connection is via the chassis. Since the schematic shows it's isolated and has a screen, I added a three core cable with earth to PSU sub-chassis. The final connections are one side of mains to wave switch to feed transformer and the other side to the voltage taps on transformer. Originally one side of the two core mains cable went direct to a wander plug! While I like authenticity, that's madness. I used a shrouded 3 pole terminal block only accessible inside the chassis.

As I said I've replaced the regular plug with a 3 pin 5A type as it fits better (original would have been either 2 or 3 pin 5A).

 
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Re: Vidor 396A - 1952

Post by Sparks » Thu May 12, 2016 7:21 pm

It was you that said 90 Volt batteries were not safe, and could kill you - not me! I think they are perfectly safe! As for transistors, ICs, solid state etc, I have never liked them, and want nothing further to do with them now that I am retired. I am a bit of a "dinasaur" when it comes to radio, and it is valves only these days. :ccg
Most of my construction projects are based on what is generally regarded as "total nonsense!" :ccb but it is good fun :qq1
Bob

 
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Re: Vidor 396A - 1952

Post by Rebel Rafter » Thu May 12, 2016 7:45 pm

Hi from RR. If anybody needs a replacement transformer for 90 volt HT then why not try one that ESR electronics have which is 12 va and 30-0-30 volt and if you ignore the centre tap you should get about 60 volts which when rectified and smoothed should give a theoretical 84 volts DC which should be adequate for later generation battery valves, i.e. the 96 series. Although seeing as this transformer has a primary rated at 230 volts rather than 240 you might get a bit more voltage out of it, I've got one of these transformers but I haven't tried it yet. The order code if anyone's interested is 300-980. Also how does this Vidor set power the filaments from the mains? Is it rectified and well smoothed? I read somewhere that these little valves have to have a well smoothed filament supply if they're powered from the mains as they only have very fine filaments. Making a suitable LT filament supply is easy enough to put together but what's not so easy is making a suitable over volts protection circuit simply because of the ultra low voltage involved so zeners are no good. I've seen an OVP circuit in a book I've got based on an op-amp type chip with adjustment right down low, so I might have a go at that. It would be a wee bit complex but well worth it to protect the filaments. Also isn't the o/p from a shaver transformer a bit on the high side? 115 x 1.414= 162 volts! RR.

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Thu May 12, 2016 8:10 pm

I use the shaver outlet transformers. Centre tapped 110-0-110. I pick up reduced ones that have unwanted front plate styles. Local shops so no evil postage.
All the 1.4V valve radios, 25mA or 50mA types in circuits for 90V HT pack are fine at 70V.
Dx91 or Dx96 is only filament current.

 
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Re: Vidor 396A - 1952

Post by Michael Watterson » Thu May 12, 2016 8:16 pm

Sparks wrote:It was you that said 90 Volt batteries were not safe, and could kill you - not me!

You claimed your reason to use 45V was safety.
It saves no money as you can't even run the PP3s half flat.

 
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Re: Vidor 396A - 1952

Post by Ed Dinning » Thu May 12, 2016 8:36 pm

Hi Gents, I've used the old style mains transformers from early video recorders. Usually plenty of different windings that can be series connected to get voltages required and they can also be used with standard battery table sets (usually a spare winding for GB if required).

I did an article for WW on this in the early 80's.

If you can't get sufficient HT volts then use a voltage doubler. At these low HT currents they work fine.

Ed

 
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Re: Vidor 396A - 1952

Post by Sparks » Thu May 12, 2016 9:29 pm

I didn't "claim" anything! This is what I said:
"I prefer to use HT of 45 to 90 Volts obtained from batteries"
In my experience, these sets work OK on 45 Volts, even less. I have even run mains sets on HT of 100 Volts just to see what happenned. Reduced volume naturally, but still very good!
Note: I said 45 to 90, and even 90 Volts I consider to be perfectly safe! (Maybe if you are soaked to the skin, you would get a minor shock, but I do expect a modicum of common sense when dealing with electricity :aaj ) and in any case, if it comes from a battery, it is certainly safer than getting it from the mains!
The Vidor LT supply comes from the smoothed HT supply, by way of a dropping resistor!
If I wanted to, I could repair the Vidor PSU, or even build a new one with little or no trouble. The main point is that I don't want to! The battery life is of no concern to me because I do not actually listen to these old radio for any length of time. The fact that I have got them working again keeps me happy. The external condition of the Vidor is such that it would take an awful ot of scraping, repainting and recovering to make it appear "as new!"
For my own experimental purposes, I have a homemade PSU with an isloation transformer feeding into a variac, rectified with a full-wave bridge rectifier (silicon, the only semiconductors that I use). I can have any DC voltage I choose from 0 to about 300 Volts! By turning it down from 90, I find that these battery sets still work down to less than 45 Volts!
Bob


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