Aurora vs Dinosaur

[Kalee20]

It can now display 625, 525, 405, 441 and 567 line pictures.
(Although 405 and 441 with bad linearity.)

I'm impressed too! I guess the switching also changes the frame frequency?

[ppppenguin]

Changing frame frequency is easy. 50Hz to 60Hz is often within range of the frame hold control though may need to tweak the height.

[Jac Janssen]

The frame frequency is indeed within the range of the frame hold control, as Jeffrey already remarked.
I included a series resistor for the hor sync for 405 and a potmeter for vertical amplitude and one for line sync and a few capacitors.
Also I had to include a few diodes in series with the supply for the LOPT (to lower the voltage; the LOPT is made for 625). 

And some switches of course.

Horizontal linearity is very bad at 405, but the characteristics of the picture can be seen nevertheless.
The little monitor has served me well during 567 line experiments.

A quarter of a century ago I adapted an old Taxan computer monitor for 405 line use.
This came in handy for aligning my Marconiphone 702 TRF section (this set has a very bad CRT, and the power supply was not yet working, so a means to see what was going on was required).
   

Jac
p.s. since I have no circuit details of the little TV, an amount of trial and error was involved...

[Murphyv310]

What ever the technical description I've yet to see 3 MHz bars displayed from the output of an Aurora converter but I'd love to be proved wrong.

Show me the screen shots.

Peter

   

[Richard_FM]

I bought a Sanyo NOS 9" CCTV monochrome monitor at Golborne, which handles 50 & 60 Hz 480 & 567 line images just fine.

[ppppenguin]

Those standards shouldn't be a problem for a simple monitor like that.

[peter scott]

Trevor, Jac's screen shots are convincing but I'm puzzled by your's

   

Peter

[peter scott]

A quick comparison (please excuse the bad photos):

Video output of the Aurora SCRF405:


Jac

Well it looks like I need to revisit my Aurora 405 line performance and apologise for suggesting less than 3 MHz performance. Will check again when I get home.

Peter  

I've been away from home for the last 3 weeks hence this rather belated response to Jac's comparison photos. I knew that I had seen one or two screen shots of the Hedghog showing what looked to me to be better in HF response than my 405 Aurora and it did surprise me when Jeffrey said that both designs share the same bandwidth specification.

There does appear to be a difference between the performance of Jac's 405 Aurora and mine. I wonder if there has been a change at some point in the resolution of the stored Test Card C image. I have never changed from the image that my Aurora was shipped with and mine does not display 3MHz bars on my HMV901 that is perfectly capable of displaying them.

Peter

[Jac Janssen]

Hello Peter,

Some photo's (quality not too good, again) of the Auroras and Hedghog; this time on the old adapted Taxan monitor.

Aurora SCRF:
   

Hedghog:
   

Aurora multi-standard converter (old model):
   

Since I do not have a receiver standby that does well over 3 MHz, no photos of that.
It could very well be that the RF response between the Aurora and Hedghog is somewhat different.

Note: only later I noticed that the camera taking the photo of the Aurora TCC must have been moved - it is not as sharp as in reality.
Since everything was stowed away already, I just left it at this...

The Aurora MSC has a reduced bandwidth, but this will rarely be visible on very old sets.

Jac
p.s. I bought my Aurora SCRF in December 2010 new from Crowthorne tubes (Gerry H)

[ppppenguin]

The Aurora acquires its testcard image from the video input. There's no facility to insert a digitally generated image. I wonder if something went wrong when capturing the image.

Worth feeding it with an external 625 line TCC to see what happens.