Cap Replacement

[AndrewLincs]

Splendid ...

10 bulbs ordered!

Regards

Andrew

Ohh .. 15th post may I have the password please?

[Jamie-Skinner]

PM'd

[AndrewLincs]

PM received ... Thanks

Regards

Andrew

[Yorkie]

As to polyester caps - the axial ones - that is the wires come out each end like the ones that they're usually required to replace ('waxies'), a good supplier that caters for small orders for vintage radio enthusiasts, is Savoy Hill. There's no VAT to add to their prices, P&P is just £2.50, free on orders over £30, and they have a good range. For those who like to 'stuff' old caps, (which doesn't include me), the 630V ones sold by Savoy Hill are nice and small. They also doe silver mica ones, but those tend to only be used in the 'front end' tuning stages (and in IFTs), and rarely go faulty.

http://www.savoy-hill.co.uk/capacitors.htm

As to whether you should change caps or leave them in place, enough has been said about 'that' cap, which should always be routinely changed. Also, mostly on AC/DC receivers, there will be a mains suppression cap across the mains input, which will invariably be a 'waxy' which should not be left in situ. This can be clipped out and discarded and even if not replaced, little difference will be noticed, if any. If it is replaced, it must be with a Class X cap as they fail to safety, are self healing and are designed specifically with mains suppression in mind. These will usually be rated at 250V AC - other caps, such as the 630V ones are DC ratings. (they're found in such things as electric drills, strimmers etc)

Some AC/DC radios may have an aerial and earth socket, which will have isolating caps, usually rated at 1,000V. In my view, it's always wise to replace those caps as if the existing ones are electrically 'leaky' with one side of the mains connected to the chassis, there are safety considerations.

There are several approaches to renovating old radios and other electrical equipment. The first, is 'conservation' which means only replacing essential items to make the radio safe and operable, while conserving as much of the originality as possible, then there is 'restoration' which means restoring the radio as far as possible, into the condition it was when it left the factory. For example, the original resistors will have mostly been to a tolerance of +/- 20%, so a 1,000 Ohm resistor when the radio was new, could have ranged between 800 - 1200 Ohms. Personally, I tend to replace resistors outside of that spec, and invariably, when they are out of spec they'll be way out - usually much higher rather than lower. However, often, there will be no discernible difference in performance even with out of spec resistors. Furthermore, when checking voltages as compared with the original service data, it will often be found that there are quite wide discrepancies even with the correct components and NOS valves fitted. I've never had a Bush DAC90A which has been close to the maker's service sheet, nor any two the same. don't let it keep you awake at night!

You can't check capacitors as easily as you can resistors. It's little use putting an Ohm-meter across the cap to check if it has a high resistance - even infinity, as the cap will perform differently when it has high voltage across it in circuit. A capacitor is supposed to block DC, but allow AC (RF/AF) to pass. If it is 'leaky' in the electrical sense, all sorts of problems can ensue, from excess current being draw, damage to valves and output transformers being burnt out. It's for this reason that most restorers tend to routinely replace 'waxy' caps, which - at 60+ years old, will have long exceeded their expected service life.

Some restorers prefer to 'stuff' old way caps with the new polyester ones to make the new ones look authentic, and that's a matter of personal preference. Personally, I don't - I take the view that if the radio had conked out during its normal working life, a radio engineer would have used whatever the current replacement was at the time of the repair. I see no reason to deviate from that approach, particularly given that the components are not on show. Such things as knobs, speaker fret, backs, and dials are of course a different matter and non-original items can spoil the appearance markedly. Safety standards change over time, and for me, safety trumps originality every time, so I'd rather alter a set to make it safer than to leave it 'original'.

How much work is done on a set, and how much money is expended, will often be dictated on whether the set is rare or collectable, or just a bog standard radio of no special note. The Bush DAC90A is a commonplace radio due to hundreds of thousands having been put out on rental in the late 40s - mid 50s, and is popular with restorers. However, given that several waxy caps will need to be replaced, probably the UL41 output valve with a new/old stock one, even if nothing more needs to be done, that will addd £20 to the cost of the set. Other known problems on that set are faulty volume control/mains switch, wave-change switch, speakers, and output transformers. However, much enjoyment is derived from restoring a set to working condition, the cost of restoration needs to be added to the purchase price of the radio, with an eye to it's likely value at the end even if one has no intention to sell it in the foreseable future.

It is of course a hobby, and all hobbies involve expenditure. As I've passed through life I've come to the view that there is often little correlation between money expended and enjoyment derived. It's been our annual village show today, and there was a large vintage motorcycle display, (in fact more were not 'vintage' they were post-war 'classic' bikes). I spotted a Triumph Bonneville was for sale. It had a notice on it saying '£4,800 spent - receipts available, must sell to finance next project - £3.500 ONO'. Huh? It's perhaps a tenuous connection between classic radios and classic bikes - he's obviously enjoying himself, but at what cost?

It did remind me of some of the stratospheric e-bay prices occasionally reached for radios when punters have got a bit carried away with their bidding.

Rambled David.

[fido]

The owner of the Bonneville probably just stripped and assembled the bike and sent bits to professionals for painting, chroming, engine rebuild etc. The equivalent on a radio would be to send the cabinet to a french polisher and the chassis to an electronics repair shop. With vintage radios, like many hobbies, you can spend a fortune or do it on a shoestring. I suppose for those who know they will regularly be restoring sets in the years to come it is worth keeping an eye open for bargains in bulk quantity high voltage capacitors. It is frustrating that capacitors can't generally be salvaged from more modern scrap equipment as they will be low voltage components.

[Yorkie]

The owner of the Bonneville probably just stripped and assembled the bike and sent bits to professionals for painting, chroming, engine rebuild etc. The equivalent on a radio would be to send the cabinet to a french polisher and the chassis to an electronics repair shop. With vintage radios, like many hobbies, you can spend a fortune or do it on a shoestring. I suppose for those who know they will regularly be restoring sets in the years to come it is worth keeping an eye open for bargains in bulk quantity high voltage capacitors. It is frustrating that capacitors can't generally be salvaged from more modern scrap equipment as they will be low voltage components.

You're right of course - he'd stripped the Bonny down in a nut and bolt restoration - professional engine rebuild - crank reground, new big ends and small ends, new valve seats, speedo refurbished, paint job, wheel re-build, re-upholstered seat, new electrics. Basically, like a new bike, but as in vintage radio circles, who wants to buy a restored radio (and what exactly is 'restored'?) Same problem with kit cars - the fun is in the building and they don't then find a ready market if the builder wishes to sell.

Many people such as myself, who served an apprenticeship and earned a living 'on the tools' before climbing the 'greasy pole' of management, quickly discovered that there's much more satisfaction from working with your hands than there is 'flying a desk' and though I came 'off the too's' 47 years ago in 1964, there's rarely a day goes by when I'm not performing some task or another, and deriving much enjoyment from so doing.

As to what constitutes 'restoration', I've attached a pic which is so scary that it needs to be viwed from behind the sofa. It's the underside of an Ecko A86 ('Dougal') which had (allegedly) been professionally restored. Not got the right value resistor? No problem - string a few together in a daisy chain or two. Simples!

It helps explain why most of us only tend to buy unrestored radios.

David

[AndrewLincs]

So, the back has come off, the knobs are off, two have broken, but I guess superglue is the answer.

Dusty Chassis



Underneath.





and 'that' cap



Regards

Andrew

[AndrewLincs]

Pleased to have spent the evening listening to the fenman, it seems to be working quite well so far!

So many thanks to everyone who has helped!

Regards

Andrew

[Joe]

Jolly good.

What's next?

- Joe

[AndrewLincs]

Good question....

I'd quite like to find a Fenman 2, but planning a scour of the local car boot tomorrow and I have placed a 'wanted' ad on the local freecycle group.

Regards

Andrew