Philips capacitors
 

We all know and love the black Hunts capacitors, but what about the black Philips ones? These are in a radiogram and I wonder if they need replacing. Predictably they're all bizarre Philips values.

Re: Philips capacitors
 

Do you have a leakage tester? If they don't leak,don't change them, especially if you think the values are critical. Les.

Re: Philips capacitors
 

My first move would be to remove the output valve and check with a DMM for any positive voltage on its control grid connection. Anything more than a few tens of millivolts suggests a leaky coupling capacitor.

Martin

Re: Philips capacitors
 

I once bought a nos dealers selection box of Philips black capacitors, out of several dozen everyone was faulty and quite a few had developed hairline cracks. I don't think they are any better than the Hunts ones, I would test them and if any show faults replace the lot.
Chris

Re: Philips capacitors
 

They will be leaky...Not quite as bad as Hunts perhaps but certainly any in a critical position (audio coupling etc) should be changed. To be honest, any that are subjected to anywhere near HT voltage are likely to break down even if they do measure acceptably at the moment.

Re: Philips capacitors
 

Change the lot, 15 minutes tops, cheap time and parts.

Lawrence.

Re: Philips capacitors
 

Those are commonly known as Philips 'black pitch' capacitors. They are the standard caps in Philips sets of the 50s and are no better or worse than other consumer grade paper caps of that period.

Personally I would replace them, but I tend towards blanket recapping in these circumstances and others will have a different view.

Re: Philips capacitors
 

In my encounters with them I've found them to be worse than Hunts, haven't found a good one yet. As Lawrence says, change the lot.

Re: Philips capacitors
 

Thanks! they test reasonably OK, but I think it's better safe than sorry, and I'll be changing the electrolytics anyway, so it's not a big deal.

Re: Philips capacitors
 

I agree with Lawrence and Paul .... I've changed the lot in Philips V5/7A's etc. - all were leaky. (P.S. It's not a fun job if you wish to retain originality - and, you usually need a circuit diagram because the values are rarely visible.)

Re: Philips capacitors
 

On what? A meter or a bridge?. I've yet to find a good one......

Re: Philips capacitors
 

Bizarre values? Most I see are quite standard.

In signal coupling and decoupling applications, they can usually be replaced by standard polyester caps 400V or 630V. Where the original has a WV of 1000V or 1300V, it's usually across the mains or between mains and ground, or across a transformer or from a transformer to ground. In such applications, polypropylene capacitors should be used. Rated X2, Y2 or 1000V depending on usage.

Re: Philips capacitors
 

Absolutely! They may be written in a slightly different way from that which you are used to but normally they are standard values. Example: 47K = .047uF or 47nF or 47,000pF. 1nF = 1K = 1000pF or .001uF. 100K = 0.1uF or 100nF or 100,000pF.

You may also see (for example) 473 = 47 and 3 zero's so 47,000pF so 102 = 10 and 2 zero's so 1000pF and so 104 is 10 and 4 zero's = 10 0000 which is 100,000 which is 100,000pF or 0.1uF

Hope that helps.

Be thankful it isn't an early French radio where the capacitor values were expressed in centimetres!

Re: Philips capacitors
 

It is not just Hunts or Philips. I had to replace several Siemens paper capacitors because they were leaky in a Rhode & Schwartz SWOB.

Old paper capacitors can be assumed to be leaky or otherwise misbehaving.

Craig

Re: Philips capacitors
 

You're quite right - they aren't that bizarre - the writing just appears so. The circuit diagram (from above) helpfully has all the capacitors highlighted in black - not deliberate, but makes it easy to find them.
On removing the capacitors and testing them on my ESR meter they throw up all sorts of interesting (and completely wrong) values. Re post #11, the couple I checked in circuit tested accurately - just coincidence as on removal they were all over the place.

Re: Philips capacitors
 

Stella (from the Philips stable) used those pitch caps extensively. The pitch often crumbles away, and on any I've ever tested at their rated voltage, they've leaked like a sieve, and when tested for capacitance are all over the place - sometimes appearing to be a resistor. As far as I'm concerned, they're a replace on sight item.

First pic below is the underside on a Stella 105U before restoration. Second shows the RF bypass cap across the mains input, ready to pop. Third pic is of the seven pitch caps I replaced with polyester film ones, and a class X across the mains. Note the one on the far right on which the pitch had crumbled, exposing the cap within.

Re: Philips capacitors
 

They're known as "Tar Bombs" in some circles. There were two in a Philips radio I rebuilt recently - one across the mains as modulation-hum-killer (it was an AC/DC radio) the other on the output-transformer.

Both were replaced as a matter of course; IMHO life's too short to make it worth testing these things before replacement.

Re: Philips capacitors
 

We used to call them 'Road blocks'. Back in the 60's there were a lot of side roads around that still had blocks making up the surface....something like cobbles but not quite.

Re: Philips capacitors
 

I have had one of these pitch capacitors actually explode while in an operational circuit. It was in a Philips AC/DC set. They are similar to the "lozenge" types often used by the likes of Nordmende at the time.

Re: Philips capacitors
 

The other capacitors probably already being of the polyester type. Polyester was and is less suited for fast high voltage peaks ocurring in those specific applications, those are perfect examples for the use of an X2 and 1000V MKP capacitor respectively that I mentioned in my previous post.