Cap Replacement

[AndrewLincs]

I plan to change 'that' cap on the fenman, however I'm wondering if, while the chassis is out, I should replace all caps?

I will have to buy all the caps as I don't have any stock.

I have been pointed to a suitable replacement for 'that' cap, however when I have searched for the value dozens of differing shapes, sizes and voltage caps are in the results.

So how the heck does a newbie work out what cap to chose for a particular application?

I have considered a trip to Maplin with the parts list and just ask....

Also I assume many of the fenman caps will be common to other sets, so I assume it would be a good idea to buy a couple of each?

Regards

Andrew

[Jamie-Skinner]

Hi Andrew! I find Mark's proccess very good http://golbornevintageradio.co.uk/forum/thread-170.html
Due to my low stock, I tend to get it working and leave it, but on monday I have 200 capacitors arriving on my door aswell as loads of other supplies so rest-assured they will all be replaced.
This can be done on a digital meter aswell but is far less accurate..

[AndrewLincs]

Thanks Jamie, wise advise I think.

However, I would still like to know how to select the best modern cap for a particular application, even if I only ever replace 'that' cap!

Sage advice welcome...

Regards

Andrew

[Jamie-Skinner]

While 400V will be perfectley adequate for all applications I use 630V for most for that added security.
PolyProp' Capacitors also are ideal

[OldTickTock]

It's down to you really there are all sorts I mainly use Metalized Polyester Film (second in from left top, the yellow tubular axials), but you could use Metal-Foil Polypropylene Film. In certain circuit stages you use Dipped Silver Mica Capacitors, Ceramic Disc Capacitors etc.

I have vintage NOS mullards that I use too. Get a varied stock is all I can advise

Below is just a small sample selection of some of the types I have
Chris

[fido]

Most of the capacitors available now are radial for PCB mounting but we are usually replacing axial components so if possible it is best to stick with axial types. You then need to make sure the voltage rating is at least as high as the original for the dc parts of the circuit. Ones in ac mains parts of the circuit should be X2 rated. The other consideration is aesthetics. If you look at some of the photos of restored sets on here you will find that most of us use the yellow axial polyester type.

[ucl82]

Most of the capacitors available now are axial for PCB mounting but we are usually replacing radial components

Surely that's the other way round? Hunts and TCC etc caps are usually axial in design.
These caps from Rapid (http://www.rapidonline.com/Electronic-Co...itor/71096) are by far the cheapest available and unlike a lot of radial ones their leads are a decent length too. You would need to go for the 400vdc ones. Next up from these are the pretty yellow caps that are available from RS, Farnell, the BVWS and JustRadios.
Ceramic disc capacitors are very cheap and are suitable, I recently ordered a load of these ones (http://www.rapidonline.com/Electronic-Co...itor/74530). They are rated at 1kv so suitable for replacing tone corrector capacitors. Most other caps can be changed for 400vdc ones.

For replacing caps across the mains X2 suppression capacitors should be used, and where a capacitor goes to an external connection such as a gram socket or aerial socket it needs to be a Y2 capacitor.

[fido]

Sorry, yes I've now corrected it, getting my radials mixed up with my crossply!

[Joe]

The ones like you were shown seem to be the favourites as the have long leads and also look the part as well as being top quality.

It's for you to decide how much 'Authenticity' matters to you and how much trouble you want to go to make the insides look pretty.

I tend to go for polyester film capacitors which are often bright orange (waits to hear distant howls of anguish). When buying blind you're taking a chance on the lead length but I don't mind lengthening them.

'Block' type ones are more box-shaped and also tend to have short leads.

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What I do is look at suppliers catalogues and stock up on anything that's cheap. This means that things don't match within a radio but that doesn't bother me. If you're changing the old wax-type capacitors you can fillet them and hide the new ones inside the tube.

By the way, 'Radial' means both leads at one end and 'Axial' means one at each.

As ever, it's 'Each to their own' and you have to do make your own decision on the balance between price, quality, looks and ease of supply. Maplin's have really slashed their range of components and you'll be lucky to find much there.

It's certainly worth changing them, in my opinion, as I've found that for all that a set may initially work these other components quickly fail. Besides that it's a good way to learn. Do them one at a time and test between each one so if you do make a mistake you'll know where.

I know this isn't a definitive answer but we all have our own ideas. Put it this way, if your happy to pay for those Steve pointed you to you'll be fine but other options are available.

All the best
-Joe

[AndrewLincs]

Thank you all for your help and advice. It is valued, and I feel increasingly confident about taking the job on.

Is there any mileage in going to one of the smaller suppliers, who is aware of our needs, and requesting a cap set for a particular set?


Regards


Andrew
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