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 A 5 inch TV I made in 1967
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 Return to top of page · Post #: 1 · Written at 8:54:17 PM on 25 January 2016.
Fred Lever's avatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 197

Here is a little story about a set I made in 1967 using the RH circuit.

My Five Inch TV

Fred.


 
 Return to top of page · Post #: 2 · Written at 12:45:58 AM on 30 January 2016.
Art's avatar
 Art
 Location: Ipswich, QLD
 Member since 22 October 2013
 Member #: 1437
 Postcount: 886

This is by far my favourite.
Quite depressionary looking, you didn’t even match the knobs!

These days there are kits available to put video into an old CRT scope.


 
 Return to top of page · Post #: 3 · Written at 6:01:37 PM on 31 January 2016.
Fred Lever's avatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 197

Hi Art, yeah it would be so easy now just grab a set top box module and pipe the signals straight into interface valves to space out the sensitive chips from the high voltage bits and you have it. Maybe I should rebuild it.....nahhhhhhhh.

Oh yes the knobs, it was lucky it got knobs! I was so broke at the time. I did have a pair of locking pliers on the old tuner main shaft to shift channels was that ok?

The memories.


 
 Return to top of page · Post #: 4 · Written at 12:57:27 AM on 1 February 2016.
Art's avatar
 Art
 Location: Ipswich, QLD
 Member since 22 October 2013
 Member #: 1437
 Postcount: 886

I don’t date back that far myself Fred, let alone making things,
but this is familiar to me with some hand me down homebrew of the 60’s.

Yeah I remember that, the rotary tuner would probably just break new knobs today.
I want to say it’s not ok because you could have manufactured one!
Sometimes after the initial high of something working,
there’s limited steam left for it, and it’s hard to touch it again.

Maybe you would help me when I get to making a scope?
It’s hard to say when I can do it, but have looked for small CRTs for a couple of years.
I’ve collected two round scope tubes, but haven’t come across a transformer with a secondary to match either tube.
The requirements for me to make practical use out of one are easy as far as home-brew scopes go,
only a single channel, and preferably a HF scale into the MHz, but even just audio would be good.


 
 Return to top of page · Post #: 5 · Written at 8:04:47 PM on 1 February 2016.
Fred Lever's avatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 197

Art no problem helping you when you get there.
Just like in this TV the problems when running a CRO tube are several regarding a transformer.
The two main problems are the magnetic field from the tranny jerking the beam around and getting the required voltage for the screen.
In the past I have made 3 CROs with valves and round tubes. I have used a 902, 5BP1 and one of the DG series square Philips CRT's. In this TV I used the 5BP1 and in the AM FM tuner I used a 902 so that's 6 or so CRT things I have made.. I also used to service CRO's back in the 1990's for Jaycar so have a bit of practical experience.
Any non PDA tube I have used needed something between 800 volt to 2.5 Kv for 2" to 5" size tubes. As in this TV the EHT could be a full voltage transformer and rectifier, or, lower a voltage transformer and doubling/tripling/quadrupling, or, a chopper supply just like in a TV but less sophisticated. Lucky for me I can wind whatever tranny I need and for a TV or CRO add a shorting turn of copper or brass onto the tranny to damp the external leakage magnetic field. No I don't offer to wind a tranny!
Like you said a CRO using an old tube will be an audio or 1Mhz response but I did use such a CRO with the 5BP1 for TV work and you could see video signals, well, just, and the sweep signals were fine. You wont resolve things like colour burst pulses but will see them as a blur.
The way forward is to know what the CRT's requirement is work out if you are making an all valve or a hybrid circuit and then possibly you may use 2 or 3 trannys like I did in the AM+ FM scope set.
There are many ways about the problem. As you are a TV guy you may be more familiar with a chopper style EHT coil setup using old B/w parts running at low drive to get 2-3Kv and use 1S2 style valves. take a look at old Radio and Hobby circuits or what is on the web.
Formulate an idea and get back to me to see what I think.
I don't know how you do this on the forum site so let me know as a post on this thread when you get there. I'm happy to email stuff to you but in line with the forum rules of course.
Fred.


 
 Return to top of page · Post #: 6 · Written at 4:32:36 AM on 3 February 2016.
Art's avatar
 Art
 Location: Ipswich, QLD
 Member since 22 October 2013
 Member #: 1437
 Postcount: 886

Ok, it’s funny you mention those series of tubes. Here are mine:Image Link
The larger is 3AP1, and the small one is DG4-2. I’d rather invest effort in the smaller DG4-2.
I prefer that it’s smaller, and have also looked into scope schematics before,
and 2AP1 seems more desirable than 3AP1 because of the voltage required to drive it.
I also have hardware for the smaller one such as the socket, and a shielding bracket
and frame that goes around it.
It came built into some camera gear from ABC. I think it’s the clock generator for the camera controller.
Image Link
The transformer for this was big & heavy. Not the sort of thing I wanted to retrieve just to drive the CRT!
It’s right down the bottom in a scope housing.
Cheers, Brek.


 
 Return to top of page · Post #: 7 · Written at 9:24:26 AM on 4 February 2016.
Fred Lever's avatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 197

Just thinking more about a basic CRO more suited to testing valve equipment and using a 1" to 5" CRT.

There are thousands of these x services tube lying about I have about 10 of them in my junk boxes why not use them? While playing with valve gear I have damaged two pieces of test quipment simply because there are levels of voltage easily touched by accident with a probe that will fry the front end of a CRO for instance. I had a probe fail which spiked the fet front end of one of my CROs and a test amp had the chips fail both by brushing a plate pin oooppps.
What I should use is a valve front end CRO. The worst you can there is fry the grid of a valve and maybe blow a cap or two all very unlikely. You are not faced with tracing down a PCB with zapped chips and transistors from one end to the other.

So thinking of Breks DG4-2 and I have a 902 lying around I have thought bubbled a very basic CRO circuit which can be made with ready available radio and TV parts plus a few new bits from Jaycar or similar. I should be able to use a radio transformer for the CRT and amp supplies as you only need 600 or 800 volts to light it up and a really simple CRO will only have 7 or so TV type valves like 6BX6's that you can buy by the bucket full from ebay. A radio suphet transformer of 250 to 400 volt a side can produce the EHT and has the filament winding for the valves. The CRT needs a separate filament transformer and parts appropriately insulated.
I'll put my thought bubble circuit here and look at it as a project down the track. The idea is very no frills but once working as a breadboard design could be tarted up with range switches, some form of calibration reference and other amenities.

I wonder if any body else is interested?
Fred.

5 inch telly (File 1)
5 inch telly (File 2)


 
 Return to top of page · Post #: 8 · Written at 12:46:11 AM on 16 February 2016.
Art's avatar
 Art
 Location: Ipswich, QLD
 Member since 22 October 2013
 Member #: 1437
 Postcount: 886

I guess it’s you and me, but I understand from your schematics how the oscillator works.
It’s the first time in my head I’ve completely put a single channel scope together.

The blanking for the the dot to retrace back to the start would occur immediately on the
falling square edge of the ramp for horizontal right?


 
 Return to top of page · Post #: 9 · Written at 6:58:14 AM on 19 February 2016.
Fred Lever's avatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 197

Art, I'm not sure of the actual timing as I'm going by memory and what I built some time ago. There is a fast reset pulse that is part of the ramp action in the valve and I used that to inject back to the CRT grid and reduce the return trace which is a pest. I'm in the process of building a audio 3" CRO now. I've got the CRT power supply using a 385/385 tranny with a tripler for the EHT going the CRT lights up ok I'm working on the vertical amplifier with EF50 valves. Once I've got that sorted i'll go on to the horizontal amp and the magic millertron time base. Then I can get to the ramp and retrace blanking and sort that out in real life. The blanking pulse may be the right polarity or it may need reversing with a triode. This is all going to take some weeks as I've got some magazine articles I have to do as well and as always scratching for time. (articles are on coins nothing to do with radios!)
I might start another thread for the CRO. I'll tidy up what I have done so far on that and paste it up in a couple of days so you can see what the hell I'm doing.
Fred.


 
 Return to top of page · Post #: 10 · Written at 9:08:33 AM on 19 February 2016.
Fred Lever's avatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 197

Ok for the folks wanting some ideas about a valve CRO i'll start a thread in the Special Projects section 'Building a valve CRO from junk parts'.
Fred Lever.


 
 Return to top of page · Post #: 11 · Written at 4:31:24 PM on 31 March 2016.
Keith Walters's avatar
 Location: Sydney, NSW
 Member since 16 January 2008
 Member #: 219
 Postcount: 38

Regarding the home made TV with the green CRO screen, some years back Dick Smith (the man himself) was actually trying to buy one of the old original R&H home-brew jobs, if anybody had one for sale. I don't know if he ever succeeded.


 
 Return to top of page · Post #: 12 · Written at 5:09:12 PM on 10 April 2017.
Oziemike's avatar
 Location: Katherine, NT
 Member since 10 April 2017
 Member #: 2092
 Postcount: 1

Wow, does this bring back memories. in 1964 aged 14 I built one of these and like you I used an IF Strip and tuner scrounged from wherever I could. Many of the parts were bought in Waltham's in Melbourne, including the 5BP1. I will never forget the feelings the first picture and sound out of that project gave me. All my pocket money went into this project over about 12 months.

I went onto work in the TV and Radio Industry from 1964 as an apprentice tech at ATV 0 in Melbourne, just prior to their commencement in August 1964. In 2004, 40 years later I shifted to Climate Research work and am retiring in September this year.

Over the years I was involved in TV servicing on the side. I proudly say that knew the pioneering days of TV in Australia both on the transmission side and the receivers.

Only stumbled across this group recently!!


 
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