The Aurora 405 NTSC converter is a rare device and it's possible that there will be no more of these unique converters made. So, for that reason I'm going to fit it inside an Eddystone diecast box. That'll provide robust protection. A simple power supply employing an LM317 regulator will also be assembled in the box. Extra protection to prevent damage to the converter can take the form of a 10volt zener diode across the 9 volt supply.
Till Eulenspiegel.
My (admittedly limited) experiences of the Aurora converter was that they ran quite hot, to my mind at least. If you're building the unit into a diecast box I would give thought to removing the plastic box and allowing a bit more air to circulate around the PCB - heat can be just as destructive as mechanical damage as I'm sure you're well aware.
Hi Mike, a very good idea indeed. There's certainly no reason why the converter should remain the plastic box when it's installed in the Eddystone box. A small fan can be fitted above the PCB and a hole drilled in the box for airflow. If this this converter blows up there is little likelihood of finding a replacement.
Just over ten years ago I embarked on a project to make a 405 line colour subcarrier generator. The project was aborted because I found it difficult to produce a pure enough subcarrier.
Till Eulenspiegel.
I guess similar applies to any Aurora device, it is not a cheap item to replace and I am sure owners want them to last as long as possible.
I must admit to always disliking the tiny plastic box and someting more substantial like the Eddystone box is a great idea.
Another thing that might be good is to replace the tiny switched encoder for channel change with a larger selector switch remote from the pcb and mounted in the outer case.
A purpose made linear PSU could be housed in the same box as previously mentioned. A 7.5v supply works well with the Aurora I have found. This, at the moment, is my bench PSU.
To understand the black art of electronics is to understand witchcraft. Andrew.
I must admit to always disliking the tiny plastic box and someting more substantial like the Eddystone box is a great idea.
Another thing that might be good is to replace the tiny switched encoder for channel change with a larger selector switch remote from the pcb and mounted in the outer case..
A friend of mine has done exactly the above with his Aurora.
Just over ten years ago I embarked on a project to make a 405 line colour subcarrier generator. The project was aborted because I found it difficult to produce a pure enough subcarrier.
Is this the sort of thing that these very useful Direct Digital Synthesis chips would lend themselves to?
Hi.
I'm sure Frank Cuffe could come up with a suitable converter for NTSC 405. It also could be done with PC generated 405 and a suitable NTSC encoder I would think.
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
... allowing a bit more air to circulate around the PCB...
Rather than air, would it better to mount the PCB right up to the metal wall of the case, with a heatsink between the hot components and the case?
Showing the insides of the NTSC 405 line colour converter. No visual differences from other SCRF405 converters.
Till Eulenspiegel.
There are two more SCRF NTSC 405 line converters out there. I foolishly parted with mine during my very black days. I think one is in Poland and the person in question would do a swap with a mono one I'm sure
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
I checked the one I bought from you Trevor and mine is not NTSC, just a regular 405a.
https://vintage-radio.net/forum/showthread.php?p=1543150#post1543150
To understand the black art of electronics is to understand witchcraft. Andrew.
Showing the insides of the NTSC 405 line colour converter. No visual differences from other SCRF405 converters.
Till Eulenspiegel.
So short of gluing a heatsink to that Xilinx lump...
Is it possible to re-program a standards SCRF405 to the NTSC colour 405 version? Jeffrey might know.
Jac
Hello Jac,
I do remember Daryll saying he just got away with programming the FGPA for NTSC 405 colour. I believe the colour converter employs the same chip set as in the SCRF405 converter.
Till Eulenspiegel.
Hello Jac,
I do remember Daryll saying he just got away with programming the FGPA for NTSC 405 colour. I believe the colour converter employs the same chip set as in the SCRF405 converter.Till Eulenspiegel.
Hi.
Definitely a different chip David, I remember Darryl telling me that it required a different one which was available in the same package so it looks the same until you look at its designation.
PC generated 405 is broadcast standard and in fact higher horizontal resolution than was broadcast as there is no filtering above 3mhz, baseband mono is stunning, but we have RGB, I'm hoping to demonstrate this on a Dual Standard CTV at some point which should be very easy to do but ideally I'd require an NTSC 405 line decoder. PC syncs would have to be used as far as I am aware.
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
Hi
A bit off topic is this thread on the UKVRRR
Please read the last two posts from myself and look at the links and PDF file.
I'd like to find out if someone with better skills than myself could create an NTSC 405 line encoder to use the ready made R.G.B PC generated 405 line signal?
https://www.vintage-radio.net/forum/showthread.php?p=1544996#post1544996
Im more determined now to make or modify properly an 405 line CTV, I did come up with a chip decoder many years ago and would like to see this work.
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member
A simple colour bars generator was made for 405 lines using the MC1377 encoder IC and three 74HCT112 J - K flip-flop ICs.
A 555 timer used for blanking.
Till Eulenspiegel.
Hi.
I'm sure Frank Cuffe could come up with a suitable converter for NTSC 405. It also could be done with PC generated 405 and a suitable NTSC encoder I would think.
Hi Trevor
It would be too large of a project to take on at the moment. At the rate I work at I would need to commit months to it.
The non availability of larger FPGA's is another problem.
Just had a quick look online. The Analog Devices AD722 NTSC/PAL encoder looks like it may be able to do what you need if you are going to use PC generated 405.
In the data sheet there is a circuit for VGA to composite NTSC. It don't look very complicated but is surface mount.
They are available from Digi-Key but only in large quantity's. Also available on ebay.
Data sheet can be found here https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjkhMe6m-j9AhUMXcAKHSAhBr4QFnoECHMQAQ&url=https%3A%2F%2Fdocs.rs-online.com%2Fdc8a%2F0900766b80025912.pdf&usg=AOvVaw01ZqgMC5y9lE5EzFYhOWX-
Frank
After reading the PDF you linked to Trevor.
I see the AD722 wont be any use as the colour subcarrier frequency will be wrong for 405 lines.
Frank
@helloekco - In order to prolong the life of Aurora I would strongly advise the following:
1. Operate the unit at the lowest supply voltage possible - 7.5v works for me
2. Use the output 'F' connector to attach the unit to case or heat sink (use a couple of extra 'F' nuts to sandwich heatsink between)
In my experience the 'F' connector temperature is a very good indicator of how hot things are inside the box and the above suggestions are well worth implementing
Rgds to all
John
