GEC Radiogram model BC3658. 1935 - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

1100 man · 17th May 2020, 2:41 pm

Hi John,
What an enjoyable read! Thanks for taking the time to write it up in such detail- it was like reading a novel at times.

I was transported to a workshop far, far away whilst engrossed in your coil winding exploits- it certainly does make you wonder how they actually managed to make wire that fine! We might view early electronics as rather crude, but they (and the Victorians) were certainly masters of mechanical engineering.

I would be interested to know more about the Tuneon indicator and also the Catkin output valve and it's 'fatty' replacement. I have never actually seen a Catkin!

Nice result on the cabinet too- I think it looks better in a lighter shade.

All the best
Nick

Heatercathodeshort · 17th May 2020, 4:58 pm

The catkin valve was produced in the early 1930's based on the MOV transmitting valve. It is a miniature version of the all glass valves of the period manufactured for broadcast receiver designs.
They are incredibly reliable but very expensive to manufacture, hence they were not around for long.

It has I believe glass to metal seals and is much smaller than the glass equivalents and in the case of the output valves, the external anode is live to H.T. so you have to be careful.

There are also versions of the MH4 and some others. I have just unearthed a few. Pictures show from left to right.

Large glass MKT4 7 pin output valve fitted in the GEC discovered during first examination. It is not strictly and equivalent to the correct Catkin MPt4 7 pin but it will work OK.
The second is the 5 pin version of the MPT4 with exposed live anode. The correct valve other than the fact that the GEC has the 7 pin version without a side connection.Third is the W30 R.F. pentode, 4 is the Catkin version of the MH4 and the last one is the catkin version of the VP4B. Information from memory so it might be slightly incorrect but I'm sure an enthusiast will correct me if that is the case.

PS The Tuneon is a thin glass tube with three electrodes, two short and one of which extends the length of the neon filled tube. It is held at HT by one electrode the other being fired off by the anode current of the I.F. amplifier. When the station is tuned in the entire length of the tube electrode is 'ignited' depending on signal strength and tuning point. It works quite well. John.

M0TGX Terry · 17th May 2020, 6:01 pm

An excellent write up of an excellent restoration. Very well done. It certainly looks great in its lighter finish. I wonder if that's how it was originally and the varnish has darkened with age, as happens to old oil paintings. I have an Invicta AR49 which arrived as a plain very dark brown box. After scraping all the old varnish off with an old Stanley Knife blade, it revealed three different decorative veneers and some black stained detailing. I can't believe they'd take the trouble to produce such an elaborate job and then deliberately cover it in 'toffee apple sludge'

Ian B · 17th May 2020, 6:04 pm

Magnificent result John! I really must get around to refinishing the lid of my HMV 580 (it got scratched badly when the house clearance people I bought it from had just thrown a load of stuff on top of it in their van. Still, it was only £40 and still had its PX4s!)
I'm sure we're all looking forward to the next project of yours!
Ian Blackbourn

Heatercathodeshort · 17th May 2020, 8:39 pm

Thanks guys. It was a bit of an epic but it's tidy now. I've just got to find a spot for it in my home.
Yes Terry. the giveaway clue is to take a look at the sales booklets of the period. They all show the veneer patterns clearly. I think they just aged somewhat but probably had a slightly darker finish when new. Coal fires were the only form of house heating for millions. Add to this heavy smoking and years of bright sunlight in window alcoves and you can understand how it breaks down.
Manufacturers would often use very dark stains on lower grade wood in an attempt to cover up imperfections. After all it was only designed for maybe 15 years service and it seems such a shame that all these well made cabinets ended up on bonfires in the late 50's and 60's. Regards, John.

peter_scott · 17th May 2020, 8:50 pm

A good read and a great result and atmospheric photos too. Thanks for sharing it with us.

Peter

Heatercathodeshort · 18th May 2020, 8:17 am

Hello Nick,
Had a look through a few editions of the early 30's Wireless World last night and came up with this explanation of the catkin valve. Hope it's readable. John

alanmoore · 18th May 2020, 10:15 am

Hello John , Yet another top notch restoration , and a very highly detailed write up of what you have done. Great stuff indeed .
I am In awe of what you have achieved with this radiogram.
Best regards Alan

1100 man · 19th May 2020, 1:01 am

Hi John,
Thanks for posting the WW article and the pictures of the Catkins- I'll have a read.

I'm sure there was an article in the BVWS magazine a couple of years ago about Catkins- I'll have to see if I can find it. You have sparked my interest now!!

Cheers
Nick

Gabe001 · 19th May 2020, 8:41 am

Hi John, thanks for this write up. I have the GEC bc3440k and the case colour and finish (which I didn't modify) seems in keeping with what you have done. The chassis and valve lineup (from memory) are very similar. I think the lighter finishes bring out the characteristics of the wood veneer and lead to a more aesthetically pleasing result. Picture below, although it doesn't really do the radio justice.
Gabriel

Heatercathodeshort · 19th May 2020, 6:01 pm

Nice example you have there. Looks like a cone speaker is fitted with the adjuster in the middle. I have never been able to work out GEC model number codes or system!

I presume it dates from around 1932/3. John.

Ian B · 19th May 2020, 7:53 pm

I too have a BC3440, which I believe dates from 1934. (I've always assumed the first two numbers refer to the year).
If I remember correctly the knob in front of the speaker actuates a small variable condenser which is the tone control, the speaker is a moving coil type as you'd expect for the year. But you're right John, it does make it look more old-fashioned.

Ian Blackbourn

ekjdm14 · 19th May 2020, 10:11 pm

Quote:

Originally Posted by Heatercathodeshort

Nice example you have there. Looks like a cone speaker is fitted with the adjuster in the middle. I have never been able to work out GEC model number codes or system!

I presume it dates from around 1932/3. John.

I too have always taken the first 2 numbers in GEC models to be the trading year of introduction, as presumably backed up by my 1956 model BC5645. I'm not sure about the rest of it though!

Heatercathodeshort · 23rd May 2020, 3:05 pm

Never thought of that one! It appears to hold up but it wobbles. The 12" GEC TV has the model BT5146 from 1951. Looks good. the 1954/55 series started BT1746 etc.Not so good. We will never know. John.

G8KBG Tony · 23rd May 2020, 3:54 pm

Not sure about GEC radios but the year of most of the 1950s TVs can be calculated by -

BT5146 = 5 + 1 + 46 = (19)52
BT1746 = 1 + 7 + 46 = (19)54
BT2254 = 2 + 2 + 54 = (19)58 etc,.

Not sure if the year was development or release.

Didn't work for sets earlier than the BT1091 series and I think they gave up when they got to the BT302.

Regards,

Tony

17th May 2020, 2:41 pm	#41
1100 man Octode Join Date: Apr 2016 Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK. Posts: 1,377	Re: GEC Radiogram model BC3658. 1935 Hi John, What an enjoyable read! Thanks for taking the time to write it up in such detail- it was like reading a novel at times. I was transported to a workshop far, far away whilst engrossed in your coil winding exploits- it certainly does make you wonder how they actually managed to make wire that fine! We might view early electronics as rather crude, but they (and the Victorians) were certainly masters of mechanical engineering. I would be interested to know more about the Tuneon indicator and also the Catkin output valve and it's 'fatty' replacement. I have never actually seen a Catkin! Nice result on the cabinet too- I think it looks better in a lighter shade. All the best Nick

17th May 2020, 4:58 pm	#42
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: GEC Radiogram model BC3658. 1935 The catkin valve was produced in the early 1930's based on the MOV transmitting valve. It is a miniature version of the all glass valves of the period manufactured for broadcast receiver designs. They are incredibly reliable but very expensive to manufacture, hence they were not around for long. It has I believe glass to metal seals and is much smaller than the glass equivalents and in the case of the output valves, the external anode is live to H.T. so you have to be careful. There are also versions of the MH4 and some others. I have just unearthed a few. Pictures show from left to right. Large glass MKT4 7 pin output valve fitted in the GEC discovered during first examination. It is not strictly and equivalent to the correct Catkin MPt4 7 pin but it will work OK. The second is the 5 pin version of the MPT4 with exposed live anode. The correct valve other than the fact that the GEC has the 7 pin version without a side connection.Third is the W30 R.F. pentode, 4 is the Catkin version of the MH4 and the last one is the catkin version of the VP4B. Information from memory so it might be slightly incorrect but I'm sure an enthusiast will correct me if that is the case. PS The Tuneon is a thin glass tube with three electrodes, two short and one of which extends the length of the neon filled tube. It is held at HT by one electrode the other being fired off by the anode current of the I.F. amplifier. When the station is tuned in the entire length of the tube electrode is 'ignited' depending on signal strength and tuning point. It works quite well. John. Attached Thumbnails Last edited by Heatercathodeshort; 17th May 2020 at 5:07 pm.

17th May 2020, 6:01 pm	#43
M0TGX Terry Hexode Join Date: Sep 2005 Location: Grantham, Lincolnshire, UK. Posts: 262	Re: GEC Radiogram model BC3658. 1935 An excellent write up of an excellent restoration. Very well done. It certainly looks great in its lighter finish. I wonder if that's how it was originally and the varnish has darkened with age, as happens to old oil paintings. I have an Invicta AR49 which arrived as a plain very dark brown box. After scraping all the old varnish off with an old Stanley Knife blade, it revealed three different decorative veneers and some black stained detailing. I can't believe they'd take the trouble to produce such an elaborate job and then deliberately cover it in 'toffee apple sludge' Attached Thumbnails __________________ Terry the Morganist

17th May 2020, 6:04 pm	#44
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	Re: GEC Radiogram model BC3658. 1935 Magnificent result John! I really must get around to refinishing the lid of my HMV 580 (it got scratched badly when the house clearance people I bought it from had just thrown a load of stuff on top of it in their van. Still, it was only £40 and still had its PX4s!) I'm sure we're all looking forward to the next project of yours! Ian Blackbourn

17th May 2020, 8:39 pm	#45
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: GEC Radiogram model BC3658. 1935 Thanks guys. It was a bit of an epic but it's tidy now. I've just got to find a spot for it in my home. Yes Terry. the giveaway clue is to take a look at the sales booklets of the period. They all show the veneer patterns clearly. I think they just aged somewhat but probably had a slightly darker finish when new. Coal fires were the only form of house heating for millions. Add to this heavy smoking and years of bright sunlight in window alcoves and you can understand how it breaks down. Manufacturers would often use very dark stains on lower grade wood in an attempt to cover up imperfections. After all it was only designed for maybe 15 years service and it seems such a shame that all these well made cabinets ended up on bonfires in the late 50's and 60's. Regards, John.

17th May 2020, 8:50 pm	#46
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: GEC Radiogram model BC3658. 1935 A good read and a great result and atmospheric photos too. Thanks for sharing it with us. Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

18th May 2020, 8:17 am	#47
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: GEC Radiogram model BC3658. 1935 Hello Nick, Had a look through a few editions of the early 30's Wireless World last night and came up with this explanation of the catkin valve. Hope it's readable. John Attached Thumbnails

18th May 2020, 10:15 am	#48
alanmoore Tetrode Join Date: Mar 2009 Location: London, UK. Posts: 74	Re: GEC Radiogram model BC3658. 1935 Hello John , Yet another top notch restoration , and a very highly detailed write up of what you have done. Great stuff indeed . I am In awe of what you have achieved with this radiogram. Best regards Alan

19th May 2020, 1:01 am	#49
1100 man Octode Join Date: Apr 2016 Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK. Posts: 1,377	Re: GEC Radiogram model BC3658. 1935 Hi John, Thanks for posting the WW article and the pictures of the Catkins- I'll have a read. I'm sure there was an article in the BVWS magazine a couple of years ago about Catkins- I'll have to see if I can find it. You have sparked my interest now!! Cheers Nick

19th May 2020, 8:41 am	#50
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,641	Re: GEC Radiogram model BC3658. 1935 Hi John, thanks for this write up. I have the GEC bc3440k and the case colour and finish (which I didn't modify) seems in keeping with what you have done. The chassis and valve lineup (from memory) are very similar. I think the lighter finishes bring out the characteristics of the wood veneer and lead to a more aesthetically pleasing result. Picture below, although it doesn't really do the radio justice. Gabriel Attached Thumbnails

19th May 2020, 6:01 pm	#51
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: GEC Radiogram model BC3658. 1935 Nice example you have there. Looks like a cone speaker is fitted with the adjuster in the middle. I have never been able to work out GEC model number codes or system! I presume it dates from around 1932/3. John.

19th May 2020, 7:53 pm	#52
Ian B Hexode Join Date: May 2006 Location: Arlesey, Bedfordshire, UK. Posts: 401	Re: GEC Radiogram model BC3658. 1935 I too have a BC3440, which I believe dates from 1934. (I've always assumed the first two numbers refer to the year). If I remember correctly the knob in front of the speaker actuates a small variable condenser which is the tone control, the speaker is a moving coil type as you'd expect for the year. But you're right John, it does make it look more old-fashioned. Ian Blackbourn

23rd May 2020, 3:05 pm	#54
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: GEC Radiogram model BC3658. 1935 Never thought of that one! It appears to hold up but it wobbles. The 12" GEC TV has the model BT5146 from 1951. Looks good. the 1954/55 series started BT1746 etc.Not so good. We will never know. John.

23rd May 2020, 3:54 pm	#55
G8KBG Tony Pentode Join Date: Sep 2006 Location: Wombourne, South Staffordshire, UK. Posts: 225	Re: GEC Radiogram model BC3658. 1935 Not sure about GEC radios but the year of most of the 1950s TVs can be calculated by - BT5146 = 5 + 1 + 46 = (19)52 BT1746 = 1 + 7 + 46 = (19)54 BT2254 = 2 + 2 + 54 = (19)58 etc,. Not sure if the year was development or release. Didn't work for sets earlier than the BT1091 series and I think they gave up when they got to the BT302. Regards, Tony __________________ G8KBG - BVWS Member - BATC Member