UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Voxophone · 16th Jan 2017, 5:52 pm

The following link was very useful to me when starting out and may answer some of your questions: http://www.justradios.com/captips.html

For voltage rating, going higher does not hurt but will generally increase the physical size of the capacitor. This may be a concern if you are 're-stuffing' old capacitor cans with modern replacements, but generally modern caps will usually be smaller than the originals, even if the voltage rating is higher. This is due to improvements in materials over the years.

For electrolytics in an HT smoothing role, subject to high voltages, I tend to use 350-450V replacements to give some margin (compared with an HT of maybe 270V). These are still usually small enough to stuff inside the old cans if required.

For general use wax capacitors (apart from mains r.f. bypass) most people use 630V polypropylene types. This is largely because 630V caps are available as axial types (i.e. with leads sticking out from either end), thus matching the shape of the originals. They also tend to be roughly the same size or smaller. With the 630V rating you can’t generally go wrong for replacing waxies on radios like the AC91. Personally, I use these: http://www.ebay.co.uk/itm/10x-Capaci...-/190915805343

For r.f. bypass and other capacitors connected across the mains, you need to use X or Y rated caps. Generally these are rated for 250V AC. The 500V rating of the originals is a DC rating which I don’t think is terribly important here. If it’s going across the mains, the AC rating is what matters and X/Y types will be 250V AC for work on the UK mains. The differences between X and Y are detailed in the link at the start of my post.

I hope this helps. The capacitor minefield can be a confusing place!

16th Jan 2017, 5:52 pm	#58
Voxophone Hexode Join Date: Oct 2015 Location: Sunderland, Tyne and Wear, UK. Posts: 340	Re: Bush A.C.91 The following link was very useful to me when starting out and may answer some of your questions: http://www.justradios.com/captips.html For voltage rating, going higher does not hurt but will generally increase the physical size of the capacitor. This may be a concern if you are 're-stuffing' old capacitor cans with modern replacements, but generally modern caps will usually be smaller than the originals, even if the voltage rating is higher. This is due to improvements in materials over the years. For electrolytics in an HT smoothing role, subject to high voltages, I tend to use 350-450V replacements to give some margin (compared with an HT of maybe 270V). These are still usually small enough to stuff inside the old cans if required. For general use wax capacitors (apart from mains r.f. bypass) most people use 630V polypropylene types. This is largely because 630V caps are available as axial types (i.e. with leads sticking out from either end), thus matching the shape of the originals. They also tend to be roughly the same size or smaller. With the 630V rating you can’t generally go wrong for replacing waxies on radios like the AC91. Personally, I use these: http://www.ebay.co.uk/itm/10x-Capaci...-/190915805343 For r.f. bypass and other capacitors connected across the mains, you need to use X or Y rated caps. Generally these are rated for 250V AC. The 500V rating of the originals is a DC rating which I don’t think is terribly important here. If it’s going across the mains, the AC rating is what matters and X/Y types will be 250V AC for work on the UK mains. The differences between X and Y are detailed in the link at the start of my post. I hope this helps. The capacitor minefield can be a confusing place!