Hi From Cathy Lissen/Eveready Kenilworth??

[cathy_vintage]

Husband Ash (Ashley) here ... well I told her when she bought the radio that she should join a forum and looks like she has done just that, and got her teeth into it. I keep feeding her as much tech info as I can. My reluctance about her buying it was that I am already up to my neck restoring 7 old Honda bikes but I am in deep now and I am always up for a challenge and definitely not a quitter. I will do as much assessment as I can over the next week and get her to report back, as I definitely want this to be 'her' project, as much as possible. Cathy's dad was a lovely bloke and she tells me he was always tinkering with Radios & TC's as at one time he worked for 'Rediffusion' in Hull which had it's own cable service and sets modified to receive the cable signals. This is why this radio means a lot to her and sadly it had to be a late 30's one or nothing for her.

Fixing valve equipment has bitter-sweet memories for me. Years ago my good friend and neighbour told me that just before his wife went away on holiday abroad, the TV and the auto-washer has gone pop and would I have a look at them to surprise her when she got back. The washer was an easy fix as it just needed a replacement drain pump but the TV, an ITT Hybrid model, had been pronounced 'BER' by a TV engineer. I told him to buy a new one but he was adamant that that valve set had a picture far better than any modern set he had seen so I rose to the challenge, went to the local library for a service manual and after much head scratching I fixed it and it worked perfectly. When his wife got back she gave me the biggest roasting as just before she went away she had chosen a new washer and TV set. Hmm . Lesson learned there I think.

Quick question before I stop hijacking the missus's post's. What is the best dielectric, in capacitors of modern day type, to use on these vintage sets of the non-polarized type please? I have a trade account with Farnell & RS

Best wishes & thanks for your help .... Ash

[ms660]

"Quick question before I stop hijacking the missus's post's. What is the best dielectric, in capacitors of modern day type, to use on these vintage sets of the non-polarized type please? I have a trade account with Farnell & RS"

Polypropylene are the most common types used for general capacitor replacement, the rated maximum working voltage of the replacement needs to be at least the same as the original.

For tuned circuits then mica dielectric are the ones to use.

For any that are connected across live and neutral then the replacement must be an X type.

For any that are connected from live/neutral to earth then the replacement must be a Y type.

For any that are connected between the circuit and the outside world in a AC/DC receiver Eg: input/output sockets etc then Y type also applies.

X & Y types are safety related.

Lawrence.

[David G4EBT]

Looking at Trader Sheet 372, apart from the likely need to replace any wiring with perished insulation, (for which I always use heat resistant silicone rubber flex in vintage colours from forum member Phil Marrison ('SWB 18'), I'd suggest that as a minimum, the following components will need to be replaced before any attempt to switch on the set:

First and foremost, C21 - the audio coupling capacitor from V3 anode to V4 grid (known as 'that cap'). Its roles is to pass the audio signal, while blocking DC from getting to the grid of V4, which can damage both the valve and the output transformer if it's leaky (in the electrical sense) as it will allow DC to pass to the grid of V4. The original is .05uF - a modern replacement would be 0.047uF (630V) polypropylene.

Secondly, the twin smoothing/reservoir capacitors - C23 (8uF) and C24 (16 uF). They appear to be encapsulated in a block under the chassis. It depends on whether conservation of original appearance or simply safety and functionality is the preferred option. Most restorers would either attempt to open the block, which may be pitch encapsulated and fit new capacitors inside, or make a reproduction block, but if the under-chassis appearance isn't consider a priority, the old block can be removed, and replacement tubular capacitors fitted in place - either singly, or as a twin unit.

Thirdly, C17 - V3 triode anode decoupling capacitor - 2uF electrolytic. (Use 2.2uF 450V).

Fourthly: C19 and C22 - 50uF electrolytic cathode bypass capacitors. (use 47uF 50V).

There are lots of other coupling and decoupling capacitors which are likely to be leaky (in the electrical sense), specifically: Cs 1, 4, 5,10,11,& 12. Use polypropylene replacements.

These are just my initial thoughts on looking at the Trader Sheet - others may see things differently, which is fine. (Good news that it's a PM speaker by the way - not mains energised).

Obviously with Ash's electronic experience and skills he's off to a flying start, but there is some excellent restoration information and advice by Paul Stenning (owner of this forum), at these links:

Main site: http://www.vintage-radio.com/

Repair and restoration:

http://www.vintage-radio.com/repair-...ion/index.html

A 'Lamp Limiter' which most of us consider an essential pre-requisite when testing a set, to minimise the risk of damage. Simple to make and use:

http://www.vintage-radio.com/projects/lamp-limiter.html

There are other useful projects too - an audio output meter for example - a useful aid when carrying out alignment.

Hope that helps as bit.

As I said earlier, if you'd like me to test the valves and take a look at the set, do drop me a personal message. (The A11D rectifier valve is a B4 base, for which I have the adaptor).

(You could of course just give the set a dust and a polish, and put it on the sideboard as a 1930s icon, but I get the impression that that option isn't on the agenda!).


Have fun!

[cathy_vintage]

Thanks everyone .. David that's so kind of you. I will be in touch in about a weeks time if that's OK after Ash has, studies the various documents /old post on here, assessed the condition and ordered up the caps you suggest in key areas.

You know how it is .... you see it ..nostalgia comes flooding back...it would make a nice ornament /play prop.... then think can we get it to work .. then obsession comes into it. Sounds like we will make good friends along the way so it sounds like a nice journey.

[paulsherwin]

It sounds as if Ash knows his stuff, so we're halfway there already. Be careful though - you might both get the bug, and you'll finish up with a houseful of old radios (and even worse, old tellies)

[PsychMan]

Cathy you mentioned NOS capacitors, I really would not advise fitting such components during the restoration of this radio.

I think the consensus here is many NOS capacitors have deteriorated with age and should not be used, particularly for "that cap" (grid coupling).

Decent high rated capacitors can be easily ordered from ebay or farnells, and are in all likelihood better made than the old ones. The NOS ones may test OK, but will they behave as intended under high voltages - maybe not...

[paulsherwin]

Yes, I missed that. Waxed paper capacitors deteriorate with age not use. David gave good advice about replacements in #23, but any replacement with the correct value and voltage rating will be fine electrically, regardless of the construction technology. People generally select them on cost, appearance and ease of fitting. Some people like to preserve the original appearance under the chassis, while others use cheap utility modern caps as commercial servicemen would have done historically.

[cathy_vintage]

Originally Posted by PsychMan

Cathy you mentioned NOS capacitors, I really would not advise fitting such components during the restoration of this radio.

He tells me that the NOS ones are mainly mica one's bought in the late 80's 90's from RS but, point taken, we will just get new ones from Farnell/RS. all will be revealed when we pull out the chassis over the next couple of days. He say's should we leave the ones in the RF section alone unless they look bad as their actual value may have been critical in the setup initially. Then once working, replace one at a time, making sure the performance is not impaired?

Yes I feel we are getting the 'bug' .. but nothing wrong with that. I bet you these things were thrown away in the thousands in the 50's ->

[paulsherwin]

He is spot on with regard to changing mica and ceramic RF caps. They rarely give trouble, and there is no need to change them in the absence of a fault.

80s and 90s NOS caps will normally be fine. The dodgy ones are the earlier ones based on foil and paper technology. This obviously includes waxies but also the notorious Hunts Mouldseal sealed caps and the Supamold plastic cased caps. Basically, anything between 0.001uF and 0.2uF made before 1980 is suspect.

[Boater Sam]

Welcome to the mad house of vintage restorations!

A word of advice. Change that cap, test transformers for continuity, replace really bad wiring but try to get it working with as many original parts as possible before changing parts wholesale.

Then you can change one or two parts at a time and ensure it still works, and you then know that you have not introduced any new fault or made any errors.

Wholesale part swapping on a set that is not working usually leads to total failure due to introduced errors, frustration takes over and interest wanes, the set finishes up being dumped as being beyond repair.

[Sideband]

As I have also restored a couple of 1930's sets, I'd just like to emphasise what others have said regarding the valves, they may well be OK. It's a fallacy that old valves will be faulty. As an example, both my 1930's sets (1934 and 1938) have most of their original valves*. Rectifier and output valves are probably the most likely to be faulty but not always. Best to deal with the capacitors and wiring first, get some power safely into the set to perform basic checks and then decide what valves, if any will need replacement.

*In fact all of my valve radio's have most/all of their original valves.

[60 oldjohn]

I find it best to use Silicon wire, the modern PVC stuff can melt and not look nice. It comes in 13 colours and is available from a Forum member SWB 18 and is very reasonable with his charges.

John.

[cathy_vintage]

Hi .. Ash Here .. I ordered up a pair of 0.047uF Polypropylene caps 1kV as I was ordering from Farnell anyway but finding it hard to find axial 2.2uF electrolytics 450v other than USA stock (with long lead time and 16 GBP delivery charge!) Do you guys use another supplier other than Farnell/RS specifically for vintage TV/radio components please (like the companies used to advertise in 'Television' magazine ? Perhaps there is a reputable one selling on eBay? I can find lots of radial ones that look piddly for 450vdc WKG but with modern materials/etc maybe I am being too cautious. Is there an ESR value or ripple current that I should be working to (like with tantalum). Or again am I going over the top.

thx Ash

Just found these ... Do they look OK?

http://uk.rs-online.com/web/p/alumin...itors/7076322/

[ms660]

Those will be ok, Cricklewood do them as well, I'll leave it to you to compare cost etc.

Lawrence.

[David G4EBT]

Originally Posted by cathy_vintage

Hi .. Ash Here .. I can find lots of radial ones that look piddly for 450vdc WKG but with modern materials/etc maybe I am being too cautious. Is there an ESR value or ripple current that I should be working to (like with tantalum). Or again am I going over the top.

Don't be put off by the diminutive size of modern caps - they don't look up to the task when compared to original ones, that's true, which is why some restorers, myself included, tend to open up the old can and fit new capacitors inside it - 're-stuffing' as it tends to be called. Others don't bother - they just fit new ones beneath the chassis, and leave the old ones in place. (I've just restored two small sets in which there was no space under the chassis, so had to re-stuff the old can anyway).

If you look at post number 7 at this link, you'll see how small Rubycon electrolytics are from Farnell, but you'll also see that they're 105C rated and have high ripple capability, beyond what we need, and have a stated life of 12,000 - 20,000 hours:

https://www.vintage-radio.net/forum/...d.php?t=129294

A lot of electrolytic capacitors have no data as to ripple rating, which isn't much help when selecting replacements in demanding positions such as reservoir and smoothing circuits.
On the other hand, in less demanding positions - eg, cathode bypass, ripple isn't really an issue.

The older, rarer, and more valuable the set, the more likely it is that restorers will 'stuff' the old can or tube, but that's only about aesthetics and has nothing to do with performance.

Looking at the picture of the underside of the chassis on the Trader Sheet, C17 - the 2uF electrolytic cap - is quite a large tubular capacitor. If it's reasonable in appearance, you could, if you wish, remove the old contents and put the new 2.2uF cap inside the tube. The same could be said for other caps - C10, 12, 14, 15, 19, 22 etc. which are also in largish tubes. That's a personal choice and a different discussion from getting the set safely back into working order.

On post-war run of the mill commonplace sets I just pop in the yellow polypropylene caps, but on pre-war sets, I prefer to re-use the old container, which isn't such a big task. The pics below show an original capacitor from a 1935 Ekco radio with the contents removed, alongside a modern replacement. The second pic shows the new cap concealed in the old tube. The same goes for block capacitors. The other pics show a duff twin section block from the same radio, and a replica I made with new caps inside. Electrically, they could simply have been fitted beneath the chassis in clips, but to my mind, that's 'mending' or 'doing up' - not restoring. Not a view everyone will share, and certainly a time-consuming distraction if the prime consideration is a safe working set in the least possible time, rather than unseen aesthetics.

When it comes to resistors, again, modern 1/2 watt ones look puny and quite out of place, so many restorers including myself, tend to use 2 Watt metal film ones which are similar in size to old 1/2 watt ones.

Hope that's helpful.

[paulsherwin]

You don't have to use axial caps unless you are concerned about the appearance (and stock axials won't look original anyway). Axials tend to be a bit easier to fit though.

Electrolytic values generally aren't critical. The originals were probably -50+100%.

David is right to make the distinction between restoring and repairing, but a full cosmetic underchassis restoration is a big ask for a beginner, and this can always be done later by a future restorer. You should keep any components you replace and store them in the radio.

[cathy_vintage]

Hi Ash here,

Cathy out last night I wasn't home till late but took out the chassis and did some basic checks.

I took out all of the valves and checked out the heaters with Fluke DMM and then powered them from my bench DC supply and they all glowed nicely ......I kept the voltage around 3v as I wasn't sure on the heater voltages but sure it must be online somewhere. The scale illumination is marked as 5.5v and I think that runs off the same tranformer tapping as the valves except the rectifier one. The recifier runs off a different tapping so I kept that down to 2v . There are no secondary voltages given in the 8453 Trader sheet only winding DC resistances. There were no shorts (or any high resistance readings) on the valves from what I could see.

I got the following readings on the mains Tx

Primary total 19.5 (19.0 in the service sheet)
HT secondary 249.0 (290.0 in the service sheet)
Heater secondaries both around 0.1 ( I would need my TTi 1705 bench meter to measure accurately.
9 megohms between primary and the main chassis.

HT smoothing choke 229.0 (230.0 in the service sheet)

Speaker transformer totally open circuit on primary so obviously U/S. somewhere I have a NOS RS valve audio output transformer that looks about the same size. Unsure if this would be suitable as I think it was intended for an EL84 valve.

The circuit did differ from the Lissen, in that on the Lissen the Ext speaker sockets are wired to the primary of the output Tx, whereas on Cathy's they are in parallel with the LS voice-coil.

Loudspeaker gave a healthy noise when connected to a 1.5v cell.

Scale illumination lampholders/bulbs connected with twin flex and just hanging in cabinet but at least we have the original holders.

Underside appears untouched as all the capacitors look like the 'Hunts' originals. They seem to be voltage pulse rated rather than quoting a standard working voltage.

Tuning condenser infinite resistance between vanes, needs restringing to control knob but tension spring present.

We plan to do a 'sympathetic' restoration only replacing suspect components. I like the idea of repacking the smoothing cap block with modern electolytics. I have never seen a capacitor like that before ...I was expecting to see an aluminium can.

I use glass woven sleeving impegnated with silicone and the same insulted wire on my Honda alternator fly leads and ignition points leads so I intend to use this on wire replacements. Here is an example:-

http://uk.farnell.com/pro-power/pp14...ral/dp/1242832

Pictures are attached.

We are both loving the 'learning-curve' and the advice from everyone .. so a big thanks.

Bye from now

[cathy_vintage]

A couple more pics. Any ides why tinned copper wound around the bottom of the glass? Mains Tx looks a bit grotty. Twin flex was on it when we bought it.

[ukcol]

The gold coloured coating on the glass of the valve is there to provide screening for the valve and is connected to a wire that comes out at one of the valve base pins. This arrangement does away with the need for a separate screening can.

It is quite common for the connection between the screening material and the the wire that goes to the base to fail. It looks like someone has added some wire to improve the connection.

[ms660]

If that RS output transformer you have is designed for an EL84 it won't be an ideal match for the output valve in your receiver but it will do to get it up and running, it won't damage anything.

The receiver all looks doable so far, to check the mains transformer you could remove all the valves and bulbs and disconnect the HT from the rectifiers heater winding and disconnect the main heater winding and apply mains power and see if it runs relatively cool after half an hour or so, if it does then generally that would mean that it's ok.

If all's well then with those connections still disconnected you can check the secondary voltages just for reference and with the power disconnected for shorts in the heater and HT circuits.

If all's well there then I would replace any HT related electrolytics and the coupling capacitor that couples the anode of V3 to the grid of V4.

How you go about replacing any of the rest of the usual suspect capacitors etc is up to you, blanket changing can cause problems for some folk.

The wire wrapped around the valve in the photo looks like an attempt to reconnect the valves external metalized coating to it's corresponding valve pin, a resistance check should reveal if it's connected or not, there's no danger if it isn't and can be sorted out later on.

This post might cross.

Good luck with it.

EDIT: If checking the transformer as above then at this stage I would power it either via a safety isolating transformer or connect the mains protective earth to the chassis just in case there are insulation problems with the transformer (safety)

Lawrence.