[SOLVED] Amiga 1000 no video through DB23, works through composite

[RetroNinja]

Any ideas?

I found a similar thread about no volts on the db23. Mine measured (properly) -5V, +12V, +5

21	-12V		-12 Volts DC (10 mA max) (A500/A600/A1200)
	-5V		-5 Volts DC (10 mA max) (A1000/A2000/A3000/A4000)
22	+12V		+12 Volts DC (100 mA max)
23	+5V		+5 Volts DC (100 mA max)

Since composite works, that means the issue should be somewhere between Agnus output and DB23 connector. Maybe caps?


Oddities
- there is a DKB switcher with a dual boot ROM, it boots to 2.04
- an IN1000 1.5MB board was installed but removed
- a Derringer 030 accelerator was installed but removed

 

[Fastdruid]

There is both digital and analogue video out from the DB23.

Thinking through, if we assume analogue then I think the highest chance is a loss of either H or V sync. The A1000 doesn't have the Hybrid but instead uses discrete components. If one section failed or one of the HC244's you'd loose *one* (or more) colour(s) or lose correct colour rather than all the colours.

So I'd probably start by verifying you have both VSYNC and HSYNC from Agnus. Bit hard to read the A1000 schematics but looks to be pins 38,39 & 40 being VSYNC, CSYNC & HSYNC.

 

[lilwashu]

Some DB23-HD15 (VGA) adapters will cause the A1000 to hang on boot in case you are using one of those.

 

[RetroNinja]

Some DB23-HD15 (VGA) adapters will cause the A1000 to hang on boot in case you are using one of those.

Yes, I am using a db23-to-15 adapter. It does flash when I power up but then no sync and the monitor (Dell U2410f) goes into sleep. At first I thought maybe it was a buffered vs unbuffered adapter issue.

Does anyone know what the deal is with the 3 video outs on an A1000? Can I triple display it? Or does using one video output turn off the others? No, I'm not trying to use a triple display, this is troubleshooting question. I did notice on booting with DB23 installed, then no display, then plugging in composite, nothing showed. But a reboot and the composite came back.

 

[RetroNinja]

There is both digital and analogue video out from the DB23.

Thinking through, if we assume analogue then I think the highest chance is a loss of either H or V sync. The A1000 doesn't have the Hybrid but instead uses discrete components. If one section failed or one of the HC244's you'd loose *one* (or more) colour(s) or lose correct colour rather than all the colours.

So I'd probably start by verifying you have both VSYNC and HSYNC from Agnus. Bit hard to read the A1000 schematics but looks to be pins 38,39 & 40 being VSYNC, CSYNC & HSYNC.

Thanks for the ideas.

With no o-scope or data probe, is there a simple way to test for signal? I think the analogy will be I have a car with no gas or wheels, can I drive it?

 

[lilwashu]

If you’re using the db23 adapter and it’s causing the problem I mentioned, you won’t hear any clicking from the disk drive.

 

[RetroNinja]

If you’re using the db23 adapter and it’s causing the problem I mentioned, you won’t hear any clicking from the disk drive.

That'd require me to have a FDD installed

Regardless, you were correct! When I skipped the db23to15 adapter and went from db23-to-scart-to-converter-to-HDMI the video came up immediately. Thanks for sharing your knowledge!

 

[RetroNinja]

Now, how about opinions on filling in the big hole cut in the top...