Non-electrolytic capacitor voltages

[poppydog]

The capacitors in question were hunts ones that are in my R200/300 transistor radios, I have one or two that are cracked from top to bottom and falling to pieces and as the chassis are out of the cases it makes sense to replace them. I ended up ordering them Sunday night off ebay in the end as the major suppliers I use didn't have the ones I wanted.

Originally Posted by 1100 man

try not to take any negative comments to heart-

I don't take them to heart I just get rather irate at the narcissistic attitudes of some.

Thank you to everyone who commented/helped.

Regards
Poppydog

[Radio Wrangler]

Sometimes, buying a higher voltage capacitor gets you one which is physically larger and a nearer match in looks to an original part. With non-electrolytic capacitors, the excessive voltage rating is no problem.

One warning about high voltage rated capacitors is that if you ever acquire any large capacitance, high voltage capacitors, wire a short circuit across them. This is important if they are put away in storage. Small draughts can create electrostatic charge and the capacitor over months or years can slowly acquire a lot of charge. Things like 16uF 3kV photoflash capacitors stored in an attic for years waiting for that big linear amplifier project can become lethal if not shorted. It sounds silly, but it's a real risk with these things. Anyway, this is a long way from Roberts portables.

David

[Maarten]

Originally Posted by Biggles

I'm sure I read somewhere once that it isn't good to use a much higher voltage rated electrolytic than required due to the fact that the capacitor requires a constant small current to remain "good" and higher voltage rated ones don't receive the current required in a low voltage circuit. But that's where my knowledge/theory ends unfortunately! In practice I find that it doesn't seem to do any harm by using higher voltage rated capacitors than the circuit requires. Hope this hasn't added confusion to the thread.
Alan.

I have read that there is a rather large range that gives an optimum life time, something like 10-90% or 20-80% of the rated WV. Below the lowest percentage the capacitor might unform and above the highest percentage the risk of leakage and flashovers increases.

[GMB]

I think electrolytic capacitors gradually adopt the working voltage that they experience. This is why when left unused they gradually become 0V rated. It is best that they don't change too much.

A sudden change will then need some reforming action. The snag being that the electrolyte used for forming the dielectric in the first place is slightly different to the working electrolyte so the reforming process is not as good as when it was made and while leakage flows it dries them up.

[AC/HL]

We're getting deeper and deeper off topic here. In particular the original question had nothing to with electrolytics, which have completely different attributes and requirements to the ones asked about.
There are low voltage capacitors available now, but back then it was typical, certainly with British manufacturers, to use those 150v or thereabouts paper components, as there was plenty of room and they were cheap.
With valve receivers, the norm nowadays is change all papers (waxies, Hunts, whatever) for very good reasons, but in a transistor radio any slight leakage is usually insignificant, and unless damaged there's usually nothing to be gained by replacement.

[poppydog]

Hope I am allowed to attach this question to my thread?

My capacitors have arrived and I meant to ask this on Sunday evening whether anybody had had any experiences with a brand called TSE as googling them has turned up hardly anything?

Regards
Poppydog

[Boater Sam]

Tai Shing Electronics Components Corp. China.
Have faith, China can produce some excellent components.

[poppydog]

Thanks for that. When I googled tse it came up with a Turkish manufacturer, but the little symbol printed on the cap looks like something from the orient. They are however very jcb yellow Regards Poppydog

[1100 man]

Originally Posted by poppydog

They are however very jcb yellow

I used black thin walled heat shrink to tone mine down a bit! Black the ends in first with a permanent marker, leave about 2mm overhang of heatshrink at each end and then use a hot air gun to gently shrink the tube. The overhang folds itself over the end of the cap quite neatly. The heat shrink needs to be thin walled, non adhesive type and be a fairly good fit before being shrunk.
I had to experiment a bit to get it right, but the end result at first glance looks remarkably similar to a Hunts cap!

Cheers Nick

[poppydog]

The thought did cross my mind about painting them black . It won't be too long before I will be taking down bus numbers ... With regards to the TSE brand, following a message from the vendor, they are Triple Spiral Electronics which are his brand and are made in the far east to his spec, just in case anybody wanted to know.

Regards
Poppydog

[1100 man]

I did spray a couple with a satin black aerosol as an experiment which worked fine. I decided that the heat shrink method was a bit easier though. For my TV project, as there are a dozen or so caps sprinkled about the chassis, I thought that bright yellow was a little garish!! Especially for the larger ones.
I am quite pleased with the heatshrunk caps- they blend in pretty well with the other components, especially as the original Hunts ones were black anyway.
All part of the fun of doing it I suppose.
Cheers Nick

[FrankB]

You will also see as one member mentioned, a 350 V 'lytic in a cathode circuit that only has a few volts on it.
This was often done here (In the U.S.) because the mfg. had:
A: Them left over from another previous production run.
B: They used them in another product- or several in the same product- and got a killer deal on them from the mfg. for such a huge order.
C: They got them NOS Mil. Surplus (Like Heathkit did on tubes), for pennies.
D: Mfg's overrun. Again pennies on the dollar.
(Love those bean counters).