Pye P76F capacitors.

[rockinmark]

Split from this thread:-

https://www.vintage-radio.net/forum/....php?t=158932I

I have just been given a Pye P76F from someone that was still using it to now but wanted a DAB radio. The volume is loud on it.

The set sounded great but now I own it I need to change the wax capacitors this is where I need help I can't see what on them the only one I can read is the big one

[AC/HL]

A bit of heat will clear the wax in order to read the values, although it doesn't sound as if there's too much wrong.
The service data is here if you don't have it: https://www.service-data.com/product...11/6662/m15211.

[Viscount]

how strange,i was given a P76F yesterday for free,apart from the cabinet needs refinishing it looks almost like new internally,great sounding set and very loud indeed,hope all goes well with yours

[rockinmark]

Seems to becoming popular or is it that people that bought them new are just passing that's how I got mine. Some one has put a little Bakelite switch on the speaker wire not sure why it's a lovely switch

[Nickthedentist]

A bit of WD40 or Servisol Super 10 (switch cleaner) on a cotton bud or similar will also remove the wax to allow you to read the values.

[rockinmark]

Thanks I will take the chassis out tomorrow and have a look

[rockinmark]

Why is c37 so big

[Kentode]

Originally Posted by rockinmark

Why is C37 so big

Do you mean big physically or big electronically?

C37 is a 0.5uf/350v cap in the nfb (negative feedback) circuit.

Are you confusing it with C38/C39?

[rockinmark]

I meant actual size

[Herald1360]

0.5uF 350V paper would be rather large physically. Modern plastic film types of similar ratings are much smaller.

Why it needed to be 350V rated is more of a mystery- it's on the secondary side of the O/P TX and won't see more than a few volts. Maybe it's all that was available in non polarised caps of that value.

[Sideband]

Originally Posted by rockinmark

I meant actual size

Simple. Technology!! 0.5uF at 350V in 1954 was a big value to achieve in paper capacitors.

Modern polyester or polypropylene capacitors can be made in similar (and much higher) values in a fraction of the size.

I have a 1946 radio on the bench at the moment that has a 2uF 150V paper capacitor across the battery connections....it's only slightly smaller than the cardboard tube from a toilet roll! However a modern polyester cap of the same value (and a higher voltage) is only about an inch and a half by three quarters inch in size.

[rockinmark]

Just trying to get my head around values, am I right in thinking that these will be OK for c9, c18 and c34 I think c35 has been changed at some point should I change it as well. With regards to the big c37 0.5uf 350vdc what should I use. The other one is c41 that's on the output transformer 0.01uf 600vac what should be best to use there. The other thing that confuses me is why is the speaker connected with banana plugs on the outside

[HamishBoxer]

Modern replacement is 0.047uF and much smaller.

[Herald1360]

0.47uF or 470nF...... still much smaller, though.

[rockinmark]

Thanks for quick response So the yellow ones are OK for the first 3 caps c37 is 0.47uf what about the other c41

[Silicon]

To avoid any confusion C9, C18, C34 and C35 were originally 0.05uF 350V capacitors.

The 0.047uF 630V capacitors in the plastic bag are suitable replacements.

C41 on the PYE schematic was originally a 0.01uF 600V capacitor. You will need a 0.01uF 630V capacitor to replace it. It will probably be marked '103'.

C37 should be replaced by a 0.47uF capacitor which will be marked '474'.
The voltage rating should be 63V or greater.

[rockinmark]

Thank you silicon the problem I'm having is that I can't find a replacement for c41 I can find it in DC but not in AC do you know where I can get one from

[julie_m]

600V AC RMS is 850V peak, so a capacitor with any DC rating greater than or equal to 850V (probably 1kV) will do the job.

[Maarten]

C41 can see peak voltages, so 600VAC should indeed not be replaced by a 630VDC capacitor. A 1000VDC MKP capacitor will probably be fine in this particular case, even if it isn't rated for 600VAC.

[rockinmark]

Would this one be ok