Minimum opamp specs for video? - Page 3

dangus · 27th November 2012, 05:40 AM

When I added a video input to a 12" B&W TV to use with my Apple ][+ clone, I used an LM318 as a buffer. It was a huge improvement over using an RF modulator.

stratus46 · 1st December 2012, 06:10 PM

Quote:

Originally Posted by dangus

When I added a video input to a 12" B&W TV to use with my Apple ][+ clone, I used an LM318 as a buffer. It was a huge improvement over using an RF modulator.

Your RF modulator limited the bandwidth to around 4 MHz while your opamp approached 10 MHz His transcoder really needs to get north of 20 MHz and would be noticeable even limited to 30 MHz.

G²

nigelwright7557 · 12th December 2012, 09:13 PM

Quote:

Originally Posted by sofaspud

Probably not. The lowly 741 may be capable of some type of (very poor quality) video..

The 741 reminds me of a silly mistake I made as a junior engineer.
My boss asked for a TV video signal buffer to be added to some equipment.
So I merrily went off and picked up a 741 and tried that.
It gave a lovely black and white picture !
Of course colour info is 4.433MHZ and the 741 filtered that out nicely.
Another lesson to add to the many I had over the years.

dangus · 13th December 2012, 03:21 AM

Probably far short of 4 MHz since the Apple clone was putting out composite video with the NTSC carrier thing at 3.58 MHz.

About a year ago, a UK electronics magazine published plans for an RGB/YUV converter; probably Elektor. The US edition left that article out. A converter like that may allow a modern TV with YUV inputs to display the RGB output from a vintage computer (Amiga, Atari ST, Apple II with RGB card) or arcade game.

freax · 13th December 2012, 07:44 AM

GO AMIGA!!!

Whats your setup there?

I've owned every model of Amiga over the years.

ThyDntWntMusic · 13th December 2012, 07:50 AM

Its an A500, with 1 meg chip ram.
Mega Midget Racer accelerator at 36Mhz, FPU at 50Mhz.
A590 SCSI controller, with 1 meg "fast" ram
And 512k of super fast ram on the mega midget racer.
2gig scsi HDD, plus an external scsi CD rom

It needs more slow ram, I had an 8meg ram expansion that went between the 68000 cpu, and accelerator, but realised it was causing massive issues when trying to copy from the CD Rom to the HDD

ThyDntWntMusic · 13th December 2012, 07:55 AM

freax · 05:59 AM

lol i love the comments that sysinfo put in, "smell the rubber?"

nice performance you've got there.

http://www.amiga-hardware.com/showha....cgi?HARDID=64

Whats the part numbers of those ram chips? Maybe someone can pipe in and help out, or do you need a standard expansion port 1 meg card, plenty of those on ebay.

ThyDntWntMusic · 15th December 2012, 06:31 AM

The Mega Midget Racer has an optional 2 or 8meg expansion BOARD that plugs in to the side.

Mine has 512k on the main MMR board, but no extra fast ram on the accelerator.

I have 512k in the trapdoor, with the motherboard modified to access this as chip ram

13th December 2012, 07:44 AM	#25
freax Owner and operator of irc.tenettenba.info diyAudio Member Join Date: Sep 2007 Location: NSW	GO AMIGA!!! Whats your setup there? I've owned every model of Amiga over the years. __________________

15th December 2012, 05:46 AM	#28
freax Owner and operator of irc.tenettenba.info diyAudio Member Join Date: Sep 2007 Location: NSW	lol i love the comments that sysinfo put in, "smell the rubber?" nice performance you've got there. http://www.amiga-hardware.com/showha....cgi?HARDID=64 Whats the part numbers of those ram chips? Maybe someone can pipe in and help out, or do you need a standard expansion port 1 meg card, plenty of those on ebay. __________________ Last edited by freax; 15th December 2012 at 05:59 AM.

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27th November 2012, 05:40 AM	#21
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	When I added a video input to a 12" B&W TV to use with my Apple ][+ clone, I used an LM318 as a buffer. It was a huge improvement over using an RF modulator.

13th December 2012, 03:21 AM	#24
dangus diyAudio Member Join Date: May 2004 Location: Vancouver Island	Probably far short of 4 MHz since the Apple clone was putting out composite video with the NTSC carrier thing at 3.58 MHz. About a year ago, a UK electronics magazine published plans for an RGB/YUV converter; probably Elektor. The US edition left that article out. A converter like that may allow a modern TV with YUV inputs to display the RGB output from a vintage computer (Amiga, Atari ST, Apple II with RGB card) or arcade game.

13th December 2012, 07:50 AM	#26
ThyDntWntMusic diyAudio Member Join Date: Feb 2008	Its an A500, with 1 meg chip ram. Mega Midget Racer accelerator at 36Mhz, FPU at 50Mhz. A590 SCSI controller, with 1 meg "fast" ram And 512k of super fast ram on the mega midget racer. 2gig scsi HDD, plus an external scsi CD rom It needs more slow ram, I had an 8meg ram expansion that went between the 68000 cpu, and accelerator, but realised it was causing massive issues when trying to copy from the CD Rom to the HDD

13th December 2012, 07:55 AM	#27
ThyDntWntMusic diyAudio Member Join Date: Feb 2008

15th December 2012, 06:31 AM	#29
ThyDntWntMusic diyAudio Member Join Date: Feb 2008	The Mega Midget Racer has an optional 2 or 8meg expansion BOARD that plugs in to the side. Mine has 512k on the main MMR board, but no extra fast ram on the accelerator. I have 512k in the trapdoor, with the motherboard modified to access this as chip ram