Ferrite Pot Cores - UK Vintage Radio Repair and Restoration Discussion Forum

ALANS ANITAS · 28th Sep 2007, 9:12 pm

Many moons ago Practical Television published an article concerning the replacement of the very expensive and unreliable Gate Controlled Switches that Sony used in the KV1810 television sets. The article suggested using a home made transformer to drive a conventional transistor. This transformer used a ferrite pot core, but these appear to be no longer available. Any ideas what could be used as a replacement.?

An alternative suggestion in the article was to use transformers from the decoder panel from a Rank A823, but i doubt if anyone has a pile of these (I would like to be proved wrong ). As I have two of these sets requiring GCS's, any help would be appreciated

Regards

ALAN

KeithsTV · 28th Sep 2007, 9:56 pm

Alan

By pure coincidence I've been scanning LLJs articles from 1984 and the article I presume you are referring to is in the December 84 issue.

The line output replacement does use the Rank A823 driver transformer but the chopper replacement uses a driver transformer from the Thorn 3500 chassis. I guess you have the article but if you don't I can send you a copy.

Unfortunately I don't have any of the specified transformers but I have some old Mullard ferrite cores, which may be usable if you can determine the winding details.

Keith

ALANS ANITAS · 28th Sep 2007, 10:24 pm

Hi Keith

Thanks for your posting.

I was working from memory(brain fade?). I'm sure that a later article (1987?) used pot cores as a substitute for the A823 transformer. In must locate the right article.

Many thanks for your offer, perhaps In could contact you after I have recovered from Harpenden this sunday.

Regards

ALAN

KeithsTV · 28th Sep 2007, 10:33 pm

Hi again Alan

You are right there is a second article in February 87. If you can't locate your copy I can send a copy of the article. I'll check the ferrites I have, once I've found them in the loft and see how they compare with those specified.

Keith

ALANS ANITAS · 29th Sep 2007, 12:03 am

Thanks Keith

No hurry. I'm not going to be able to do the mod for a few months, but i thought I would ask in plenty of time.

Regards

ALAN

plaka78 · 29th Sep 2007, 3:30 pm

I can remember doing this Mod on two KV1810s and neither of them worked correctly (very small picture) in fact I nearly scrapped both sets. I had to do a modification to the start up cct to give the LT rail the correct voltage, but it was so long ago that I can’t really remember what I did. But after my mod both set worked fine. If I can remember I think the ferrite transformer was a rank A823 line driver coil

28th Sep 2007, 9:12 pm	#1
ALANS ANITAS Rest in Peace Join Date: Jun 2006 Location: North West Northamptonshire, UK. Posts: 346	Ferrite Pot Cores Many moons ago Practical Television published an article concerning the replacement of the very expensive and unreliable Gate Controlled Switches that Sony used in the KV1810 television sets. The article suggested using a home made transformer to drive a conventional transistor. This transformer used a ferrite pot core, but these appear to be no longer available. Any ideas what could be used as a replacement.? An alternative suggestion in the article was to use transformers from the decoder panel from a Rank A823, but i doubt if anyone has a pile of these (I would like to be proved wrong ). As I have two of these sets requiring GCS's, any help would be appreciated Regards ALAN

28th Sep 2007, 9:56 pm	#2
KeithsTV Nonode Join Date: Aug 2007 Location: South Bradford, West Yorkshire, UK. Posts: 2,573	Re: Ferrite Pot Cores Alan By pure coincidence I've been scanning LLJs articles from 1984 and the article I presume you are referring to is in the December 84 issue. The line output replacement does use the Rank A823 driver transformer but the chopper replacement uses a driver transformer from the Thorn 3500 chassis. I guess you have the article but if you don't I can send you a copy. Unfortunately I don't have any of the specified transformers but I have some old Mullard ferrite cores, which may be usable if you can determine the winding details. Keith

28th Sep 2007, 10:24 pm	#3
ALANS ANITAS Rest in Peace Join Date: Jun 2006 Location: North West Northamptonshire, UK. Posts: 346	Re: Ferrite Pot Cores Hi Keith Thanks for your posting. I was working from memory(brain fade?). I'm sure that a later article (1987?) used pot cores as a substitute for the A823 transformer. In must locate the right article. Many thanks for your offer, perhaps In could contact you after I have recovered from Harpenden this sunday. Regards ALAN

28th Sep 2007, 10:33 pm	#4
KeithsTV Nonode Join Date: Aug 2007 Location: South Bradford, West Yorkshire, UK. Posts: 2,573	Re: Ferrite Pot Cores Hi again Alan You are right there is a second article in February 87. If you can't locate your copy I can send a copy of the article. I'll check the ferrites I have, once I've found them in the loft and see how they compare with those specified. Keith

29th Sep 2007, 12:03 am	#5
ALANS ANITAS Rest in Peace Join Date: Jun 2006 Location: North West Northamptonshire, UK. Posts: 346	Re: Ferrite Pot Cores Thanks Keith No hurry. I'm not going to be able to do the mod for a few months, but i thought I would ask in plenty of time. Regards ALAN

29th Sep 2007, 3:30 pm	#6
plaka78 Pentode Join Date: Jul 2007 Location: Salisbury, Wiltshire, UK. Posts: 174	Re: Ferrite Pot Cores I can remember doing this Mod on two KV1810s and neither of them worked correctly (very small picture) in fact I nearly scrapped both sets. I had to do a modification to the start up cct to give the LT rail the correct voltage, but it was so long ago that I can’t really remember what I did. But after my mod both set worked fine. If I can remember I think the ferrite transformer was a rank A823 line driver coil