mikel@ccvaxa.UUCP (03/18/86)
And they say where there is smoke there is fire. Well I had some smoke coming out of my Amiga, but no fire. I have some graphic tubes here at work and I was going to hook them up to my Amiga using the RGB outputs (I already have a VT240 head hooked up and working with no problems.) I hooked up the RGB connectors and then the composite sync. I was trying not to have to use the h+v sync separately, but I later determined that it was needed. (FYI the connections were properly made) Having no luck with this tube because it required separate h+v sync I decided to try another tube (Silicon Graphics), as soon as I had turned on my machine, I smelled smoke! I turned off the machine, took off the cover (my machine is out of warranty by a few months) and inspected it. After looking at all the components and seeing nothing burnt, I decided to plug it back in and watch for the fire. Well, nothing smoked again, but what did happen is that the picture on the VT240 is not as sharp as it was before. I suspect I fried some of the filtering for the video. One of my questions is has anyone else tried to hook up there Amiga to other graphics tubes and had any problems? I know lots of people have hooked up to the Sony monitor and a few others, but I was wondering about tubes used for high res graphics ( >= 1K x 1K). Do these types of tube draw too much juice for the outputs from the Amiga? Does anyone have the specs for RGB signals and output levels? Another question is does anyone know which chips, caps, resistors, and inductors make up the filtering for the video? I don't want to have to reverse engineer the board. I will be using the scope and looking at the signals in the mean time. Thanks for any info, Mikel Matthews Gould Computer Systems Division, Urbana, IL inhp4!uiucdcs!ccvaxa!mikel mikel@gswd-vms
dillon@CORY.BERKELEY.EDU (Matt Dillon) (03/22/86)
I learned very fast to double check all my custom connections to any computer before turning on the juice. Specifically... I once blew out an I/O chip + 4 TTL chips (situated in random places on the board) when I had a bad ground connection to a circuit running from an external power supply. -Matt
grr@cbm.UUCP (George Robbins) (03/23/86)
> I have some graphic tubes here at work and I was going to hook them up to my > Amiga using the RGB outputs (I already have a VT240 head hooked up and > working with no problems.) I hooked up the RGB connectors and then the > composite sync. I was trying not to have to use the h+v sync separately, but > I later determined that it was needed. > (FYI the connections were properly made) Be warned that the horizontal and vertical sync outputs are not intended to drive a monitor directly (for genlock only). Too much load on them and your machine will stop working - no smoke though... > ...as soon as I had turned on my machine, I > smelled smoke! I turned off the machine, took off the cover (my machine is > out of warranty by a few months) and inspected it. After looking at all the > components and seeing nothing burnt, I decided to plug it back in and watch > for the fire. Well, nothing smoked again, but... Sounds like it might be some kind of grounding problem - check between the system and the monitor to make sure that theres no AC voltage between the grounds... > Another question is does anyone know which chips, caps, resistors, and > inductors make up the filtering for the video? I don't want to have to > reverse engineer the board. I will be using the scope and looking at the > signals in the mean time. Some HC244's buffer the chip outputs and feed into a D-A resisitor network - this goes into the three big transistors which drive the outputs through more resistors with a takeoff of the composite video chip (MC1377). Shouldn't be too hard to trace, check resistors, caps and transistor with a meter first - also try composite video output to see if you lost a color in that chip... > Mikel Matthews Gould Computer Systems Division, Urbana, IL > inhp4!uiucdcs!ccvaxa!mikel mikel@gswd-vms -- George Robbins - now working with, uucp: {ihnp4|seismo|caip}!cbm!grr but no way officially representing arpa: cbm!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)