Marconiphone VT55A - any info? - UK Vintage Radio Repair and Restoration Discussion Forum

thermionic · 5th Oct 2019, 1:34 pm

Hello all.

After looking through my volumes of ‘the red book’, I can’t find any circuit that matches my set. It’s a single channel Ally Pally set, but states ‘AC Only’ which I guess is due to the CRT heater transformer you can see mounted top right.

The Mazda CRT appears to be original, but I could be wrong.

Any leads, please?

Many thanks.

Simon.

AC/HL · 5th Oct 2019, 2:22 pm

That appears to be a CRT booster transformer, so wouldn't be original.

Nuvistor · 5th Oct 2019, 2:36 pm

There is a large transformer on the bottom right of the middle photo, presume a mains transformer.
Agree the small transformer feeding the CRT will have been fitted later in the sets life, either to boost the tube or isolate it for a heater/cathode short.

line sync · 5th Oct 2019, 5:56 pm

Hi Simon
That is a Plessey chassis and you will find it in the red book pre 1953 models volume 111.
That chassis was used in lots of sets , look for regentone T15L ,philco BT1410.
There is also a trader sheet for the Plessey chassis number 984/T10.

Robin

thermionic · 5th Oct 2019, 7:50 pm

Ahh...Many thanks, Robin.

I would never have looked at Plessey, a mixed bag of valves in this chassis.

Any idea why Marconiphone went to Plessey for this model?

Cheers. SimonT.

Heatercathodeshort · 5th Oct 2019, 8:38 pm

The Plessey chassis is very reliable and they must have wanted something that worked for more than a week after the 1807 saga!
Unfortunately the Mazda CRM121B fitted in these chassis had a very poor life. The good news is that the large mains transformer has heater taps for all the reliable tubes. You can fit virtually any 12" tube in this chassis. John.

FERNSEH · 5th Oct 2019, 9:43 pm

Surprise to see Mazda valves in a Marconi TV set. Apart from the 6SN7GT and 6D2 which have the Marconi equivalent types B65 and D77 all the others have no Marconi equivalents.
Plessey did later on supply Marconi with TV chassis which employed rebranded Mullard valves either as Emitron or Marconi.
On an historical note, in the 1920s Plessey made radios for Marconi and did so up to the formation of Electrical and Musical Instruments, EMI.

DFWB.

thermionic · 5th Oct 2019, 9:49 pm

Hi John.

Well,it’s good news that it can accommodate other tubes without too much fuss. I’m in the process of sorting out my sets collected over many years to a new store, so I’m unearthing items I’ve forgotten about!

I have a few different Marconiphone / HMV sets to sort out...😬

Thanks for the information.

SimonT.

FERNSEH · 5th Oct 2019, 9:53 pm

The screen looks quite small. Is it twelve inch CRT?

DFWB.

thermionic · 5th Oct 2019, 9:53 pm

Hi David.

I must admit, I was surprised to learn that this is a Plessey chassis. But the valve types used on this chassis, as you say, are not what you would expect to encounter in a Marconiphone/ HMV set.

thermionic · 5th Oct 2019, 9:54 pm

Quote:

Originally Posted by FERNSEH

The screen looks quite small. Is it twelve inch CRT?

DFWB.

It is 12’’ David.

FERNSEH · 5th Oct 2019, 10:08 pm

It's the later version of the Plessey Mark 1 chassis which has the electric picture shift controls. A small amount of DC is introduced into the scanning coils and adjustment is done by the multi-turn controls positioned above the pre-set slider controls.

I have a Philco console TV set which has a very American look about it. Like the Marconi VT55 it also has the Plessey Mark 1 chassis. However, in this set the valves are with the exception of the EL38 are all Brimar and instead of those Mazda 6F1 pentodes the chassis has 8D3 or 6AM6 B7G base valves.

DFWB.

5th Oct 2019, 1:34 pm	#1
thermionic Heptode Join Date: Apr 2003 Location: Cornwall, UK. Posts: 988	Marconiphone VT55A - any info? Hello all. After looking through my volumes of ‘the red book’, I can’t find any circuit that matches my set. It’s a single channel Ally Pally set, but states ‘AC Only’ which I guess is due to the CRT heater transformer you can see mounted top right. The Mazda CRT appears to be original, but I could be wrong. Any leads, please? Many thanks. Simon. Attached Thumbnails __________________ The honesty of imperfection..........

5th Oct 2019, 2:22 pm	#2
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: Marconiphone VT55A - any info? That appears to be a CRT booster transformer, so wouldn't be original.

5th Oct 2019, 2:36 pm	#3
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: Marconiphone VT55A - any info? There is a large transformer on the bottom right of the middle photo, presume a mains transformer. Agree the small transformer feeding the CRT will have been fitted later in the sets life, either to boost the tube or isolate it for a heater/cathode short. __________________ Frank

5th Oct 2019, 5:56 pm	#4
line sync Heptode Join Date: Sep 2009 Location: Kinver, Staffordshire, UK. Posts: 634	Re: Marconiphone VT55A - any info? Hi Simon That is a Plessey chassis and you will find it in the red book pre 1953 models volume 111. That chassis was used in lots of sets , look for regentone T15L ,philco BT1410. There is also a trader sheet for the Plessey chassis number 984/T10. Robin

5th Oct 2019, 7:50 pm	#5
thermionic Heptode Join Date: Apr 2003 Location: Cornwall, UK. Posts: 988	Re: Marconiphone VT55A - any info? Ahh...Many thanks, Robin. I would never have looked at Plessey, a mixed bag of valves in this chassis. Any idea why Marconiphone went to Plessey for this model? Cheers. SimonT. __________________ The honesty of imperfection..........

5th Oct 2019, 8:38 pm	#6
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Marconiphone VT55A - any info? The Plessey chassis is very reliable and they must have wanted something that worked for more than a week after the 1807 saga! Unfortunately the Mazda CRM121B fitted in these chassis had a very poor life. The good news is that the large mains transformer has heater taps for all the reliable tubes. You can fit virtually any 12" tube in this chassis. John.

5th Oct 2019, 9:43 pm	#7
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Marconiphone VT55A - any info? Surprise to see Mazda valves in a Marconi TV set. Apart from the 6SN7GT and 6D2 which have the Marconi equivalent types B65 and D77 all the others have no Marconi equivalents. Plessey did later on supply Marconi with TV chassis which employed rebranded Mullard valves either as Emitron or Marconi. On an historical note, in the 1920s Plessey made radios for Marconi and did so up to the formation of Electrical and Musical Instruments, EMI. DFWB.

5th Oct 2019, 9:49 pm	#8
thermionic Heptode Join Date: Apr 2003 Location: Cornwall, UK. Posts: 988	Re: Marconiphone VT55A - any info? Hi John. Well,it’s good news that it can accommodate other tubes without too much fuss. I’m in the process of sorting out my sets collected over many years to a new store, so I’m unearthing items I’ve forgotten about! I have a few different Marconiphone / HMV sets to sort out...😬 Thanks for the information. SimonT. __________________ The honesty of imperfection..........

5th Oct 2019, 9:53 pm	#9
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Marconiphone VT55A - any info? The screen looks quite small. Is it twelve inch CRT? DFWB.

5th Oct 2019, 10:08 pm	#12
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Marconiphone VT55A - any info? It's the later version of the Plessey Mark 1 chassis which has the electric picture shift controls. A small amount of DC is introduced into the scanning coils and adjustment is done by the multi-turn controls positioned above the pre-set slider controls. I have a Philco console TV set which has a very American look about it. Like the Marconi VT55 it also has the Plessey Mark 1 chassis. However, in this set the valves are with the exception of the EL38 are all Brimar and instead of those Mazda 6F1 pentodes the chassis has 8D3 or 6AM6 B7G base valves. DFWB.