I have searched, and read and searched a again and read other stuff - but I don't see the difference as too why I should use one brand/type of cap over another. Please impart some of your wisdom

So recapping my Tasman 175 and the two smoothing caps on the power supply are 8μF axial electros. Other wisdom gleaned from this page {thanks} suggests I'm well advised to use the 450V units.

All good so far, but when I do a search on element 14 I get three potential candidates. Two vishay and one multicomp.

I can see no real difference between them (except the multicomp is $2.03 and the cheapest vishay is $7.03).

Why would I choose one over the other? What on the data sheets is the 'thing' I'm not understanding to help me with my decision?

Electrolytics generally come in two maximum operating temperature ranges: 85C and 105C. Usually, the 105C are more expensive and better value. The biggest killer of electrolytics is heat, so 105C is better.

Another major characteristic is working life in thousands of hours. These days it's a stretch to find anything better than 2,000 hours available to the average punter.

Of the two brands you mentioned, the Multicomp has the higher temp rating and actually quotes working hours.

Vishay is usually considered a premium brand and has various series of capacitors, each with slightly different characteristics. In this case, element14 only carries 85C Vishays with no hours listed and has priced them at a premium.

Given just that choice I'd opt for the Multicomp.

However, as axials are no longer popular, you'll usually find a greater range to choose from in radials -- which can often be used quite readily in place of axials.

Thanks heaps - I hadn't considered the heat - yes 105C would be the preferred way to go, dumb of me not to pickup on that.

If I went radials would heatshrink/spagetti be recommended to help keep those pesky legs apart or do most people not bother?

dumb of me not to pickup on that

Not at all. Learning begins with reading and questions, and speaking of reading, I would suggest these two books:

Valve Radio and Audio Repair Handbook -- CE Miller 1982 (UK)

Takes a very practical approach to the subject.

Radio Receiver Servicing -- John T. Frye 1955 (USA)

Written in a folksy, accessible style, this is also a good practical book for beginners.


would heatshrink/spagetti be recommended

As a rule of thumb, yes.

Another issue for high voltage electros in valve radio power supplies is current rating. The Input to Filter cap on the rectifier cathode works pretty hard.

In this application, generally speaking, the larger the cap is, physically, the longer it will last. Within reasonable limits, I generally go for higher capacitance and the highest working voltage you can get - 450v or more.

If the original cap is 8μF, you can generally go over this by a factor of 3, say 24μF. Those original wet electros often started life at about this value. Much more than this stresses the rectifier. But a higher value cap will reduce hum markedly.

In old TVs, the same thing applies for cathode bypass caps in the vertical output stage. I will normally replace an original 50μF with 220μF simply because a modern 47μF 16v cap is such a tiny device it can't dissipate the ripple current and chops out fairly quickly. Going higher with the voltage with a 47μF in this position increases the ESR and impacts on the performance of the stage (affecting the bottom linearity).

Oh - I should point out I am a design engineer in my day job and the products I design are bought by users who expect them to last much longer than the Chinese alternatives......

Old Nerd

I stock the top quality caps at a lot cheaper than Element 14. I can get you the 600 volt electros for 4 bucks each and they are 105c plus all the yellow caps.

There is a capacitor limit on the valve itself. If its a 5Y3/ #80 with a B voltage around 250 I will not use 450V ones & many of them are crap: Lots of failures. I will not go under 500V for a cap that is on that valve, or any rectifier that behave like it, or Silicon Diodes when feeding heater valves.

So I would take up the offer on 600V, replace every waxed paper cap in it, & check the resistors as you go. Out of spec resistors are not helpful & I replaced 7 in one set last week.

Irrespective of what I have seen written this week; Rarely in commercial fixing of hundreds of sets, have I seen a Wax Paper cap that does not leak: Leaking caps affect performance and are liable to fail further: Not get better. On that basis, with me, if it leaks its a dud and will be replaced.

Due to the leakage of them (over 99.9%) one rarely bothers testing them. Time is better spent tossing them.

Marc

On that basis, with me, if it leaks its a dud.

Ditto.

Yes Marcc, I agree.

Tonight I recapped an HMV F3 TV chassis. I replaced 23 paper caps, the remainder had already been replaced with Philips polys many years ago.

Out of curiosity, I tested them. Two were NOT leaky and one of those was open circuit!

As far as the resistors go, nothing was more than 20% out, even the 2 x 1k 1W B+ droppers to the vertical, despite both being completely charred they measured OK! (I replaced them anyway).

All the can electros came up perfectly after 100 hours on the dim bulb.

Many solid state devices, diodes and transistors are leaky too.
You don’t toss all them out.
I would be scratching to have any working vintage transistor radios if I did.
Most brands of paper caps were leaky when new, as thats the nature of the insulating material.
But, I suppose experience does tell us that if the paper cap is grossly leaky or its the brand that
has two black stripes on one end, then they should be replaced.
I have no objection to recapping, and have done so many hundreds of times.
But the whole job needs to be appraised first.
I have also spent many hours repairing man made faults due to recapping and pulling bits out for testing, by others.
With my old apprentices it was the "stick", but I guess thats illegal now.
JJ

GTC, are you serious that modern electro's are only designed to last 2000 hours??? At 12 hours a day use that equates to 167 days! Not even a year??? Does that mean I must replace my electro's twice per year if I have the radio on 12 hours per day???

are you serious that modern electro's are only designed to last 2000 hours???

An electrolytic's actual lifetime depends on how hard it's flogged in terms of temperature, voltage and ripple current, and that depends on the application in question. Electros in a computer power supply may have a very hard life compared to those in a valve radio,

Serious manufacturers have to quote a lifetime in their specifications, and so they publish figures based on numerous de-rating parameters and the definition of end-of-life can differ among manufacturers, too.

The common or garden Aluminum electros that you're likely to buy from retailers are usually rated at no better than 2,000 hours, unless you specifically purchase long life series electros made by the likes of Panasonic, Nichicon and Vishay:

http://www.nichicon.co.jp/english/products/pdfs/e-uld.pdf

https://industrial.panasonic.com/cdbs/www-data/pdf/RDF0000/ABA0000C1026.pdf

http://www.vishay.com/ppg?28411

The 2000 hour rating is for a cap that is running at max temperature, max rated current and max voltage. No engineer worthy of the name would run their parts like that.

It's generally regarded as EOL when it gets to 66% of its rated capacitance, for example. It still works after that and a good design will allow for the cap to deteriorate quite significantly without stopping the device from working.

You use derating formulas to calculate your EOL in a given application. And consider the reputation of the manufacturer.

And also use more capacitance than you need, because it WILL deteriorate.

Hmmn it puts things in perspective than when the original capacitors have lasted 60yrs and still work! T had thought the modern equivalents to be far superior! Obviously not... It's a wonder they don't make them a plug in component like valves?

The technology has not changed very much but the parts have got smaller......

Google "The great capacitor plague" for some interesting reading on the subject!