Round Screen Project - UK Vintage Radio Repair and Restoration Discussion Forum

dominicbeesley · 15th Jan 2008, 12:00 am

Hello all,

Inspired by the previous Round Screen projects here is my first attempt at designing and building my own 405 line TV from scratch using junkbox components except for the DH3-91 screen which cost me £20.

Not quite there yet with linearity and bandwidth but at least you can tell what it's trying to display!

I'm afraid my design isn't as elegant as Balloon Valve's using lots of transistors. Now for a lot of tweaking to get this down to a reasonable component count.....

Dom

42 inch plasma screen - rubbish!

dominicbeesley · 15th Jan 2008, 4:36 pm

The tube is a Mullard one for 'scopes - must have had good eyesight!

I think I'll make a cabinet and buy a hamster to watch it!

Dom

HMV 1120 · 15th Jan 2008, 8:24 pm

Awwr! Sweet! I want one!! ^^

rob77 · 16th Jan 2008, 8:36 am

Great work!!! I love it!!

How very strange we all are! My mother-in-law has just got the new 70inch JVC and it looks good but here we are raving about a 1 incher!! Its bloomin great!!

Lets see more like this!

Cheers for sharing it with us.

Rob

dominicbeesley · 17th Jan 2008, 11:22 am

He he,

Glad you all like it! Spent a while mucking about with it last night, here are some more pictures and cct diagrams...

Most pics show it running from the Aurora at 405 lines, however as a punt I thought I'd feed it some PAL, the last picture of James May is the result - no adjustments necessary though its a bit blurry!

Not sure why I'm getting so much streaking on the picture does this indicate poor HF or LF response or is it some other kind of instability?

Also not quite sure what to do about the cramped frame, the wave form (shown on the scope) is pretty linear.

The valve is an 6SN7GT but will probably get replaced with something a bit less power hungry.

Any hints on the circuit appreciated - its all my own made up work and probably a bit weird!

Dom

dominicbeesley · 17th Jan 2008, 11:23 am

More pics...

Note the label that says to CRT Y should go to the grid of the field output valve!

15th Jan 2008, 12:00 am	#1
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Round Screen Project Hello all, Inspired by the previous Round Screen projects here is my first attempt at designing and building my own 405 line TV from scratch using junkbox components except for the DH3-91 screen which cost me £20. Not quite there yet with linearity and bandwidth but at least you can tell what it's trying to display! I'm afraid my design isn't as elegant as Balloon Valve's using lots of transistors. Now for a lot of tweaking to get this down to a reasonable component count..... Dom 42 inch plasma screen - rubbish! Attached Thumbnails

15th Jan 2008, 4:36 pm	#2
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: Round Screen Projects II The tube is a Mullard one for 'scopes - must have had good eyesight! I think I'll make a cabinet and buy a hamster to watch it! Dom

15th Jan 2008, 8:24 pm	#3
HMV 1120 Hexode Join Date: Jan 2007 Location: Weeting, Norfolk. Posts: 465	Re: Round Screen Projects II Awwr! Sweet! I want one!! ^^ __________________ Real radios glow in the dark M6GLD

16th Jan 2008, 8:36 am	#4
rob77 Tetrode Join Date: May 2005 Location: Norwich Posts: 87	Re: Round Screen Projects II Great work!!! I love it!! How very strange we all are! My mother-in-law has just got the new 70inch JVC and it looks good but here we are raving about a 1 incher!! Its bloomin great!! Lets see more like this! Cheers for sharing it with us. Rob

17th Jan 2008, 11:22 am	#5
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: Round Screen Projects II He he, Glad you all like it! Spent a while mucking about with it last night, here are some more pictures and cct diagrams... Most pics show it running from the Aurora at 405 lines, however as a punt I thought I'd feed it some PAL, the last picture of James May is the result - no adjustments necessary though its a bit blurry! Not sure why I'm getting so much streaking on the picture does this indicate poor HF or LF response or is it some other kind of instability? Also not quite sure what to do about the cramped frame, the wave form (shown on the scope) is pretty linear. The valve is an 6SN7GT but will probably get replaced with something a bit less power hungry. Any hints on the circuit appreciated - its all my own made up work and probably a bit weird! Dom Attached Thumbnails Last edited by dominicbeesley; 17th Jan 2008 at 11:31 am.

17th Jan 2008, 11:23 am	#6
dominicbeesley Octode Join Date: Nov 2004 Location: Hebden Bridge, West Yorkshire, UK. Posts: 1,885	Re: Round Screen Projects II More pics... Note the label that says to CRT Y should go to the grid of the field output valve! Attached Thumbnails