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Build your own 405 TV

 
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10843

I was rummaging through my library and with Brian's recent construction thread fresh in my mind, I came across this manual from 1949. A constructional guide to building your own High Definition receiver.

I thought the circuit might be of interest to our B&W members and perhaps generate some debate. Maybe some may have already seen it or indeed built it, if so then please show the results here. You have to admire the simplicity of the whole circuit. If anyone is interested in the whole manual and perhaps even considering building the TV, I can scan the entire manual for you. Its very detailed, has all the component lists and is not as large as you may think.

tv-01.jpgtv-02.jpgtv-03.jpgtv-04.jpgtv-05.jpgtv-06.jpgtv-07.jpg

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Topic starter Posted : 23/09/2016 5:24 pm
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Cathovisor
(@cathovisor)
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Posts: 5477

I was very impressed to see the grounded-grid RF amplifier in the input - an excellent choice.

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Posted : 23/09/2016 6:40 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10843

The suggested valves are as follows:-

Sound

V1, V2, V3, V5 6F12 or EF91 V5 EF37 or 6SJ7

V4 6D2 or EB91

V6 6V6/G-GT

Vision

V1 EC91

V2, V3, V4, V7 6F12 or EF91

V6 6D2 or EB91

V6 EL91

Sync

V1 6F12 or EF91 or EF50

Frame

V1 EA50

V2 L63

Line

V1 6P28 or EL38

V2 EA50

V3 EY51

Power

V1 GZ32

CRT

CRM121 or CRM9

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Topic starter Posted : 23/09/2016 7:41 pm
Jayceebee
(@jayceebee)
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Posts: 1631

The PSU looks a bit unusual with the full wave rectifier V1 being fed from a 300-0-350v winding. Is there some reason for this in the design or was the transformer some sort of surplus component. Are R1 and R2 the same value?

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Posted : 23/09/2016 8:24 pm
Brian Cuff
(@briancuff)
Noble V-Ratter Rest in Peace
Posts: 2063

I too, am impressed with the grounded grid first vision stage, Mike. The set looks quite easy to make with the most simple frame time base that I have seen - I assume that L4 are the scan coils! One of the problems with these early home-constructed magnetic deflection TVs is that of the wound components. Are there details of these in the text, Chris? BO transformer with a tertiary output winding is fairly unusual but I should imagine that any simple LOPT (6P28 was fairly common as a LOPV in those days) would do and the coils for the RF stages would not be taxing at all grin_gif. Not like BT1618 IF coils  embarassed. Thanks for the information, Chris. I know that haven't seen that booklet as I normally buy those that I see.

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Posted : 23/09/2016 8:35 pm
crustytv
(@crustytv)
Vrat Founder Admin
Posts: 10843

There are instructions on winding the sound and vision coils, there's talk of using Aladdin formers and instructions for tuning inductances for London or Birmingham, number of turns and the s.w.g. gauge wire to use.

The power and coils used were by a Stewart transformers, the scan and focus coils were Plessey. I guess off the shelf parts in those days.

There's instructions for forming/bending/cutting the chassis'. I'll get it all scanned for the data library

tv-08.jpgtv-10.jpgtv-09.jpg

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Topic starter Posted : 23/09/2016 9:01 pm
Brian Cuff
(@briancuff)
Noble V-Ratter Rest in Peace
Posts: 2063

Jayceebee said
The PSU looks a bit unusual with the full wave rectifier V1 being fed from a 300-0-350v winding. Is there some reason for this in the design or was the transformer some sort of surplus component. Are R1 and R2 the same value?  

I would have thought that the difference was down to a simple draughting error. I can't think of another reason unless 650V was some other circuit requirement for 650V such as an oscilloscope EHT supply with the 350V winding used with a half-wave rectifier duno_gif - I doubt it though!

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Posted : 23/09/2016 9:49 pm