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Old 04 January 2019, 00:03   #1
blainelocklair
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Location: USA
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A500 Has No Video Output

Hello everyone!

I just bought a "tested and working" US NTSC A500 on eBay. The ad showed it booting to the Kickstart disk screen on an original 1084. I received the computer yesterday, along with a Gotek FDD emulator and an A520 for video connection. The A520 was tested by the Gotek seller before shipping and worked. I have tried connecting the Amiga 500 throug the A520 by composite and RF to my TV, along with the monochrome composite to my TV, with no signal at all. The TV just sits on "No Signal". Nothing is being output from the Amiga.

Here's what I've done so far to try to help the problem:

* Checked for +5, +12. and -12 from the PSU at the plug to the back of the Amiga. All are fine.
* Swapped the CIA chilps, no change. I read online that swapping these can impact bootup.
* Did the "warm touch" test of all major chips. All are warm, indicating at least power, except for Gary and the Kickstart ROM (Rev. 5 board)
* Pulled the Gary chip, very gently sanded the legs with a Magic Eraser, iso alcohol clean of chip, socket, and board.
* Pulled the Kickstart ROM and ME'd and iso alcoholed it.
* When the system first came home, the original FDD would click looking for a disk. It has since stopped. I've installed the Gotek and everything comes up fine on it.
* The drive light originally would turn green for about five or six seconds, then turn completely off. Since installing the Gotek, the drive light stays on consistently.
* reseated Paula, Denise, and Agnus. Was super-careful to pry gently from both sides of the socket very slowly. Came out with no issues, socket intact. Cleaned the pins with Magic Eraser and iso alcohol, cleaned the socket with iso and q-tips. Gently reseated all chips. Fired it back up and no change. No signal to the TV at all.

Also, no 512K memory/battery upgrade ever installed, so no battery corrosion from the trap door side. Also, caps lock flashes red for about one second at startup then turns off. No further flashes.

Something else I noted: I can turn caps lock on and off, but only about six times. It just turns off the light and leaves it off after any subsequent presses.

Where do I look next?

Thanks!
Blaine
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Old 04 January 2019, 00:40   #2
Mick
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I'm not exactly an expert with diagnosing Amiga hardware faults but on PC's a solid floppy light was usually a sign that the floppy cable was in the wrong way around, so maybe double check that. It might be worth putting the old floppy back in until you get everything else sorted, if you can get it clicking for a disk to be inserted it's a good sign I think.

In terms of display try plugging the composite cable directly into the Amiga and bypass the A520 just to rule that out?

edit.. It might be worth swapping the CIA's back as well if you've only switched them around once just to see if anything changes, perhaps one of them is faulty.

Last edited by Mick; 04 January 2019 at 00:52.
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Old 04 January 2019, 00:50   #3
blainelocklair
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Thank you for your input. I felt like the Gotek was installed backwards when compared to the original FDD. The Gotek has the upgraded LCD screen, and when I installed it the same way that the original FDD was installed, it popped up a message stating I "might" have the cable on backwards. I flipped the cable and the message went away. I'll transition back to the FDD until the system is working properly.

All suggestions are welcome! Thanks for your help!

Blaine
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Old 04 January 2019, 06:56   #4
blainelocklair
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Well, I would say I am a bit embarassed, and I am, but also not really. Everything is working fine on the Amiga. As it turns out, I found the problem through the "If you eliminate the impossible, whatever remains, however unlikely, must be true" principle. First, I tried a different TV (newer) to see if it'd make a difference. It didn't. I finally decided to check the continuity on my composite cable, even though it was brand new from Amazon with gold plating and shielding. Turns out, no continuity in the yellow part of the RCA cables. Grabbed a different cable and tested for continuity. Found continuity immediately. Hooked it up to the Amiga, and picture appeared immediately. Dang.

You know, it's so often the simple stuff that gets us. I would not have suspected that quality gold plated, shielded cables would have ever been the problem. But, they were. At least I also now have a very clean Amiga with cleaned chips, all reseated, and ready to go! Even got the Gotek to load its first game. You know it would have to be my favorite A500 game of all time: SOTB.

Thank you to everyone that made suggestions and inputs into this problem. A good reminder to me to never trust, always verify. It's wonderful to have this Amiga back in business!

Thanks!
Blaine
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