general valve query - EAF42 substitution

[geofy]

Hope this is the right thread, it is about a radio valve The EAF42 which doesn't seem to have an equivalent. It is a single diode pentode rf if.

If the diode section wasn't needed (it is usually strapped to cathode and separate suppressor grid in this case) is there a pentode valve that could be used in its place

Thanks

Geof

[Steve_P]

Well there is an Equivalent - W150.

You could try an EF42 ?

Cheers,

Steve P

[Ian - G4JQT]

Any help here?

http://tdsl.duncanamps.com/show.php?des=EAF42

Ian

[paulsherwin]

You can usually sub an EF41. The EAF42 is variable mu despite the even code number, and the pentode characteristics are quite similar. The pinout is the same apart from the diode connection which is an IC on an EF41.

Some manufacturers specified either an EF41 or EAF42 as an IF amp without any component changes, presumably choosing the valve on availability.

I'm sure somebody suggested somewhere that an EAF42 could be used as a sub for an EF41, because apparently they're cheaper

Paul

[mickjjo]

The early 1950s Ekco car radios used a total of 3 EAF42s, R.F. amp, I.F. amp/detector and A.F. preamp, I think the idea was to cut down on the number of types needed as replacements, the R.F. and A.F. ones could be subbed with EF41s. .

Regards, Mick.

[geofy]

Thanks Steve,

My book for the W150 listed 6F16 6CJ5 62VP and EF41, there can't be much difference between the EF41 and EF42 the book doesn't list the EF42.

Geof

Originally Posted by Steve_P

Well there is an Equivalent - W150.

You could try an EF42 ?

Cheers,

Steve P

[geofy]

Thanks Ian

Two more possibilities that I didn't know about

Geof!

Originally Posted by Ian - G4JQT

Any help here?

http://tdsl.duncanamps.com/show.php?des=EAF42

Ian

[geofy]

Thanks Paul

That's very good information, I wondered whether it was because of the availability of a particular valve whether all sections are used or not. I am not altogether sure why just the single diode was used unless AGC and detection are all taken from it instead of two diodes in some circuits.

Geof.

Originally Posted by paulsherwin

You can usually sub an EF41. The EAF42 is variable mu despite the even code number, and the pentode characteristics are quite similar. The pinout is the same apart from the diode connection which is an IC on an EF41.

Some manufacturers specified either an EF41 or EAF42 as an IF amp without any component changes, presumably choosing the valve on availability.

I'm sure somebody suggested somewhere that an EAF42 could be used as a sub for an EF41, because apparently they're cheaper

Paul

[geofy]

Thanks Mick

That's a little surprising as the anode voltage is rated at 250 max. It makes assembly easier if any valve can go in any holder, on the rf if pre-amp section at least

Geof

Originally Posted by mickjjo

The early 1950s Ekco car radios used a total of 3 EAF42s, R.F. amp, I.F. amp/detector and A.F. preamp, I think the idea was to cut down on the number of types needed as replacements, the R.F. and A.F. ones could be subbed with EF41s. .

Regards, Mick.

[geofy]

As you can see, I haven't mastered the art of replying to everyone in one post, apologies for that

Thanks for all the excellent information.

Geof

[ukcol]

Hi Geof

Do you need to substitute at all? The EAF42 appears to be available from John Fish at Wilson Valves for example.

Home page

http://www.flashbacksales.co.uk/wilsonvalves/wvindex.htm


EAF42 page

http://www.flashbacksales.co.uk/wilsonvalves/p8.htm

[geofy]

Hi Colin

Thanks for the links, I don't need a valve just yet, I was looking at a circuit of this valve with the diode section unused and wondered why that particular valve had been choosen.

I have made a note of the links as they could come in handy, good pages

Thanks appreciated

Geof

Originally Posted by ukcol

Hi Geof

Do you need to substitute at all? The EAF42 appears to be available from John Fish at Wilson Valves for example.

Home page

http://www.flashbacksales.co.uk/wilsonvalves/wvindex.htm


EAF42 page

http://www.flashbacksales.co.uk/wilsonvalves/p8.htm

[Leon Crampin]

The EF41 and the EAF42 pentode section have very similar characteristics and can be interchanged. The EF42 is an entirely different device - a high slope straight mu pentode designed for TV IF amplifiers and is unsuitable for use in an AM radio.

There was an EAF41 which has g3 connected internally to the cathode. This prevented set designers from using g3 as an AGC delay diode (rather dubious) so the EAF42 was born to allow this. This is why this valve breaks the Philips rule of odd numbers for variable mu valves and even numbers for straight mu valves. (There are other exceptions such as the EF37(A), again, as a result of modifications).

The pin outs allow you to wire the holder to accept either valve - but not according to the data sheet. All of the EF41 pins marked as "IC" by Philips are in fact connected to the cathode so you can rewire the base to take either device (diode anode connected to cathode) very easily. All of this applies equally to the UF41 and UAF42 and I suggested this substitution in sets such as the DAC90A some time ago.

NOS Philips (Holland) UAF42s were available very cheaply at one time, wheras good UF41s were getting a bit expensive.

Leon.

[ukcol]

Originally Posted by geofy

Hi Colin

Thanks for the links, I don't need a valve just yet...............................

Geof

'Got it round my neck again.

[geofy]

Originally Posted by ukcol

'Got it round my neck again.

What a valve, nice jewellery, the links are very helpful

Thanks
Geof

[paulsherwin]

Originally Posted by geofy

That's very good information, I wondered whether it was because of the availability of a particular valve whether all sections are used or not. I am not altogether sure why just the single diode was used unless AGC and detection are all taken from it instead of two diodes in some circuits.

The EAF42 was intended to be used in short superhets without an EBC41 type valve to supply the diodes. In the octal era such sets had used an EBL31 output valve to house the diodes, but this was difficult to achieve with smaller output valves. The single diode could be used for both detection and AGC, but this isn't a very satisfactory arrangement and the valve was soon replaced with the dual diode EBF80 (later EBF89). Possibly this resulted in warehouses full of EAF42s making them cheaper than EF41s.

Paul

[geofy]

Thanks Leon

I have since found the Z150 is equiv. of EF42, a rimlock B8A valve. The history of the EAF41 is very interesting. What the valve and set manufactures did to try to outdo each other! You would have thought they could have given it another sequence number to keep the type in the same family.

I was curious about the EAF42 after looking at the circuit of the Regentone Multi 99 table radiogram that used this valve in the first IF stage. My family had one once but it went a long time ago, I have since seen not very good examples for sale.

Geof

Originally Posted by Leon Crampin

The EF41 and the EAF42 pentode section have very similar characteristics and can be interchanged. The EF42 is an entirely different device - a high slope straight mu pentode designed for TV IF amplifiers and is unsuitable for use in an AM radio.
Leon.

[geofy]

This could be why they where connected as a pentode in the short IF with the EBC41 in the secondary IF/AGC/Detector as in the Regentone. My Philips 650A has the EBL1 side contact with the two diodes!

Geof

Originally Posted by paulsherwin

Possibly this resulted in warehouses full of EAF42s making them cheaper than EF41s.

Paul