LA4730 pot core - UK Vintage Radio Repair and Restoration Discussion Forum

Hermit6345 · 27th Jun 2017, 10:45 am

I have a few of these in my spares box. Google isn't much help. Has anyone got any info on these items? The only other markings are 8720K which means nothing to me. TIA

kalee20 · 27th Jun 2017, 1:43 pm

Nothing in my 1978/79 Mullard Quick Reference Guide (although the LA series does exist).

m0cemdave · 27th Jun 2017, 3:13 pm

Book 3 Part 4 of the Mullard Technical Handbook lists the RM cores with full data, but unfortunately mine is dated December 1979 and only goes up to LA4576. If you can find someone with a later edition they may be able to help.

Hermit6345 · 3rd Jul 2017, 5:28 pm

Thanks for looking both. I will continue to see what comes up in the future.

cheers.

Philips210 · 4th Jul 2017, 4:44 pm

Hi

I had a look in my two Quick Reference Guides dated 1984 and 1988 but unfortunately they're not listed. It would seem they are part of the RM series as Dave mentioned.
With reference to page 411 in the 1988 Quick Reference Guide:

RM5 (LA4000 series)
RM6-R (LA4100 series)
RM7 (LA4200 series)
RM8 (LA4300 series)
RM10 (LA4500 series)

I'm fairly sure there were RM12 and RM14 pot cores which I take it are physically larger than say the RM10.

On the back cover of the guide is listed the Mullard approved suppliers for their components. Regarding Ferrite for Inductors, it lists STC Electronic Services, Sasco, and Hawnt. I appreciate these businesses may not be operating now but I was thinking if anyone has a catalogue for the listed suppliers then the relevant technical data may be to hand.

Out of interest, do you have a pic of your LA4730 and approximate dimensions?

Regards
Symon.

Terry_VK5TM · 5th Jul 2017, 1:35 am

Mullard ferrites became Ferroxcube and they are still around. Not sure they will be of any help for such an old product though.

http://www.ferroxcube.com/

Terry

Hermit6345 · 10th Jul 2017, 1:44 am

Thanks Symon and Terry. I do remember that I purchased mine from STC or whatever their retail outlet was called at the time. I will try to take a photo of one of mine. I can measure the coil former diameter as well. Their construction looks like the RM series cores that are available on eBay etc but your data would indicate that mine are larger than RM10. Someone may well have a catalogue which lists the larger cores. I guess that I must have had a catalogue when I bought my cores in the 1980s. STC were selling large job lots of quartz xtals, all frequencies, shapes and sizes at the time and I have the feeling that they were closing their retail outlet. I may be wrong though.

Terry_VK5TM · 11th Jul 2017, 3:48 am

I thought I had a substitution list for various brands of ferrites, but a dig through the boxes in the shed has failed to turn it up.

If it turns up, I'll scan and post it here.

Terry

Ed_Dinning · 11th Jul 2017, 9:14 pm

Hi Hermit, a quick look through my data does not show any numbers going up as far as LA4730, I do seem to remember one of the forum members publishing a cross ref list a few years ago, anyone remember this?

The old standby of the STC "yellow bible" from 1982 only lists up to LA4547

Ed

27th Jun 2017, 10:45 am	#1
Hermit6345 Rest in Peace Join Date: Oct 2006 Location: North Wiltshire, UK. Posts: 638	LA4730 pot core I have a few of these in my spares box. Google isn't much help. Has anyone got any info on these items? The only other markings are 8720K which means nothing to me. TIA

27th Jun 2017, 1:43 pm	#2
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,087	Re: LA4730 pot core Nothing in my 1978/79 Mullard Quick Reference Guide (although the LA series does exist).

27th Jun 2017, 3:13 pm	#3
m0cemdave Octode Join Date: Feb 2009 Location: Bletchley, Buckinghamshire, UK. Posts: 1,223	Re: LA4730 pot core Book 3 Part 4 of the Mullard Technical Handbook lists the RM cores with full data, but unfortunately mine is dated December 1979 and only goes up to LA4576. If you can find someone with a later edition they may be able to help.

3rd Jul 2017, 5:28 pm	#4
Hermit6345 Rest in Peace Join Date: Oct 2006 Location: North Wiltshire, UK. Posts: 638	Re: LA4730 pot core Thanks for looking both. I will continue to see what comes up in the future. cheers.

4th Jul 2017, 4:44 pm	#5
Philips210 Nonode Join Date: May 2007 Location: Redruth, Cornwall, UK. Posts: 2,578	Re: LA4730 pot core Hi I had a look in my two Quick Reference Guides dated 1984 and 1988 but unfortunately they're not listed. It would seem they are part of the RM series as Dave mentioned. With reference to page 411 in the 1988 Quick Reference Guide: RM5 (LA4000 series) RM6-R (LA4100 series) RM7 (LA4200 series) RM8 (LA4300 series) RM10 (LA4500 series) I'm fairly sure there were RM12 and RM14 pot cores which I take it are physically larger than say the RM10. On the back cover of the guide is listed the Mullard approved suppliers for their components. Regarding Ferrite for Inductors, it lists STC Electronic Services, Sasco, and Hawnt. I appreciate these businesses may not be operating now but I was thinking if anyone has a catalogue for the listed suppliers then the relevant technical data may be to hand. Out of interest, do you have a pic of your LA4730 and approximate dimensions? Regards Symon.

5th Jul 2017, 1:35 am	#6
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,340	Re: LA4730 pot core Mullard ferrites became Ferroxcube and they are still around. Not sure they will be of any help for such an old product though. http://www.ferroxcube.com/ Terry

10th Jul 2017, 1:44 am	#7
Hermit6345 Rest in Peace Join Date: Oct 2006 Location: North Wiltshire, UK. Posts: 638	Re: LA4730 pot core Thanks Symon and Terry. I do remember that I purchased mine from STC or whatever their retail outlet was called at the time. I will try to take a photo of one of mine. I can measure the coil former diameter as well. Their construction looks like the RM series cores that are available on eBay etc but your data would indicate that mine are larger than RM10. Someone may well have a catalogue which lists the larger cores. I guess that I must have had a catalogue when I bought my cores in the 1980s. STC were selling large job lots of quartz xtals, all frequencies, shapes and sizes at the time and I have the feeling that they were closing their retail outlet. I may be wrong though.

11th Jul 2017, 3:48 am	#8
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,340	Re: LA4730 pot core I thought I had a substitution list for various brands of ferrites, but a dig through the boxes in the shed has failed to turn it up. If it turns up, I'll scan and post it here. Terry

11th Jul 2017, 9:14 pm	#9
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: LA4730 pot core Hi Hermit, a quick look through my data does not show any numbers going up as far as LA4730, I do seem to remember one of the forum members publishing a cross ref list a few years ago, anyone remember this? The old standby of the STC "yellow bible" from 1982 only lists up to LA4547 Ed