UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Offered and Wanted Messages > Sets, Parts and Service Information Wanted (private buyers only, no swaps)

Notices

Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

Reply
 
Thread Tools
Old 20th Jan 2021, 6:36 pm   #1
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Wanted hf coil

This is for a Philips 940 trf radio the HF coil/tx is o/c the service manual gives it at 15k ohm .
Attached Thumbnails
Click image for larger version

Name:	IMGP0063.jpg
Views:	111
Size:	107.7 KB
ID:	225019   Click image for larger version

Name:	IMGP0064.jpg
Views:	108
Size:	143.6 KB
ID:	225020  
vinrads is offline   Reply With Quote
Old 20th Jan 2021, 9:40 pm   #2
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 3,159
Default Re: Wanted hf coil

I suspect that the original will be very hard to find, but I'd guess from the circuit (a larger area of the circuit would be helpful) that it's a combined anode resistor and radio frequency choke (RFC).

If that guess is correct, then wiring in a 15k resistor is series with a 2.5mH inductor might get things going. There's hardly any current flowing so a miniature inductor will cost next to nothing.

Hopefully, others could confirm?

B
__________________
Data beats opinions most times... that's my opinion, though I have no data on that.
Bazz4CQJ is offline   Reply With Quote
Old 20th Jan 2021, 10:48 pm   #3
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Re: Wanted hf coil

Thanks Bazz yes it is the ht and rf choke ,feed to the detector ,I have it working using a interstage tx , I noticed different coils alter the audio quality, the original is in the freezer, I have always heated the capacitor blocks to remove the innards ,a bit messy though , Mick.
vinrads is offline   Reply With Quote
Old 21st Jan 2021, 12:37 am   #4
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 3,159
Default Re: Wanted hf coil

How does the freezer help put?

B
__________________
Data beats opinions most times... that's my opinion, though I have no data on that.
Bazz4CQJ is offline   Reply With Quote
Old 21st Jan 2021, 9:00 am   #5
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,571
Default Re: Wanted hf coil

Hi, freezer is a good way to be able to remove pitch as it makes it very brittle. It can still fly everywhere when chipped off though.

A choke and / or resistor were my thoughts as well but not enought schematic visible to be certain. Within reason the choke can be as large as you like (economics probably dictated its size in production). Then adjust series resistor to get voltages correct, consistent with reasonable sound.
In use the choke may even have been wound with resistance wire .

Ed
Ed_Dinning is offline   Reply With Quote
Old 21st Jan 2021, 9:35 am   #6
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Re: Wanted hf coil

There is nothing to be gained by showing more of the cct ,HT is fed to the bottom of the choke, one of my jobs today will to remove the choke from pitch filled box, and hope the break is accessible , well ! you never know, Mick.
vinrads is offline   Reply With Quote
Old 21st Jan 2021, 10:56 am   #7
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,571
Default Re: Wanted hf coil

Hi Mick, I may have some suitable chokes if you need one. The old style wound as several "piles" will probably work fine

Ed
Ed_Dinning is offline   Reply With Quote
Old 21st Jan 2021, 3:29 pm   #8
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Re: Wanted hf coil

Hi Ed ,I have the set working using a push/pull driver tx secondary windings, the two coils in series gives 11.6k I have had the tx a long time ,something tells me if I fit it I will need one in the near future, so I would be interested in your offer can you let me know the dimensions please as I would like it to fit in the original place. Mick.
vinrads is offline   Reply With Quote
Old 21st Jan 2021, 4:06 pm   #9
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,571
Default Re: Wanted hf coil

Hi Mick if you can post a picture when extracted and approx size I'll see what in my collection matches up.
Any idea of its max current rating?

Ed
Ed_Dinning is offline   Reply With Quote
Old 21st Jan 2021, 5:26 pm   #10
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Re: Wanted hf coil

Hi Ed to fit inside the original screened box it needs to be 53mmx 43mm x40 mm, otherwise 65mmx 50mmx 55mm then I will have to make a box for it , thanks ,ps current les than 1ma about 0.75ma Mick.

Last edited by vinrads; 21st Jan 2021 at 5:45 pm.
vinrads is offline   Reply With Quote
Old 21st Jan 2021, 7:30 pm   #11
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,571
Default Re: Wanted hf coil

Hi Mick, 2 types here as shown below, both about 40mm long and 15 dia
The one out of the can has fixing bolts and is 120R, the wire ended one is 12R

Yours for the postage

Ed
Attached Thumbnails
Click image for larger version

Name:	100_1282.jpg
Views:	18
Size:	54.2 KB
ID:	225100  
Ed_Dinning is offline   Reply With Quote
Old 21st Jan 2021, 8:12 pm   #12
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Re: Wanted hf coil

Hi Ed thanks for that but I think it needs to have some iron in it ,I tried something similar to what you have there, didn't work. Mick.
vinrads is offline   Reply With Quote
Old 22nd Jan 2021, 1:25 pm   #13
vinrads
Nonode
 
Join Date: Feb 2009
Location: Chesterfield, Derbyshire, UK.
Posts: 2,645
Default Re: Wanted hf coil

Picture of the choke, the wire is very thin 0.06mm Mick.
Attached Thumbnails
Click image for larger version

Name:	IMGP0065.jpg
Views:	8
Size:	95.0 KB
ID:	225138   Click image for larger version

Name:	IMGP0066.jpg
Views:	9
Size:	87.4 KB
ID:	225139  
vinrads is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 12:50 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.