No signal from VGA->HDMI converter \ VOGONS

No signal from VGA->HDMI converter

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First post, by dimka

Posted on 2022-06-18, 19:10

dimka Offline

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Hello.

I have few retro PC I started to build for retrogaming but my only available display is modern ultrawide monitor. I purchased VGA-to-HDMI converter (https://gembird.com/item.aspx?id=9876) and tried to boot up with one of my rig but display was blank. Overall PC is working okay: it's powered up and I've heard POST single beep.

At first I thought that converter is broken and to verify I plugged it in to my old laptop with VGA output but it worked ok up to 1920x1080 resolution.

I switched back to old rig and still blank. Tried with MB built-in video — blank. I switched MB and tried another videocard (PCIe this time) — and got BIOS image for a second but then it went to power saving mode (video: https://streamable.com/ajxhvj).

My original idea was to use my primary modern display for retro rig, so before I start ebay'ing for more age appropriate monitor with VGA input I wanted to ask, whether it looks like the only option or am I missing something?

Note: VGA->HDMI converter require external power and it was powered separately, not from the retro rig USB, so I don't think that's the issue.

Reply 1 of 5, by darry

Posted on 2022-06-18, 19:20

darry Offline

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My guess is that either the adapter or the monitor cannot handle 70Hz .

DOS VGA text mode is 720x400 @ 70Hz .

Most VGA DOS games are 320x200 @ 70Hz , which gets line-doubled by the VGA card to 640x400 @ 70Hz (which is what gets output through the VGA connector).

Also, the specs for the converter say "Output video resolution remains the same as input video resolution", so the monitor needs to supports 70Hz over HDMI for this to work with the adapter you currently have .

Reply 2 of 5, by dimka

Posted on 2022-06-18, 19:58

dimka Offline

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Monitor is 60Hz. But I am confused about that first second of BIOS detecting IDE drives was visible. Also I tried another display with 100Hz support and it was not showing anything.

I quickly searched for VGA monitors available in my local stores and found Dell E1715S, which is 60Hz as well. I was thinking about getting this monitor just for retro setups but now I'm unsure.

Reply 3 of 5, by TehGuy

Posted on 2022-06-18, 23:04

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dimka wrote on 2022-06-18, 19:58:

I quickly searched for VGA monitors available in my local stores and found Dell E1715S, which is 60Hz as well. I was thinking about getting this monitor just for retro setups but now I'm unsure.

from what I can find, the monitor you've linked has a range of 56 - 76 Hz vertically; it should be fine. Now, at native (1280x1024) it can only do 60 but it should be able to boost the refresh rate when the resolution drops, provided you're using VGA.

Win98+DOS: C3 Ezra-T 1.0AGHz / P3-S 1.26GHz, 128MB RAM, AWE64 + Orpheus + Audigy 2 ZS, Ti 4200, 128GB SD card
Win XP SP3: C2Q 9650, 4GB RAM, X-Fi Titanium, GTX 750
PowerMac G4 QS 800MHz + GeForce4 Ti4200, OS 9
PowerMac G5 DP 1.8Ghz + ATi x800 XT, Leopard

Reply 4 of 5, by Plasma

Posted on 2022-06-19, 00:27

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Most of those cheap VGA to HDMI adapters can only handle standard Windows resolutions. 640x480, 800x600, etc. Without support for 720x400 you won't see DOS text modes.

Reply 5 of 5, by darry

Posted on 2022-06-19, 01:41

darry Offline

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Plasma wrote on 2022-06-19, 00:27:

Most of those cheap VGA to HDMI adapters can only handle standard Windows resolutions. 640x480, 800x600, etc. Without support for 720x400 you won't see DOS text modes.

Indeed, nor will these adapters typically do 640x400@70Hz (line doubled 320x200@70Hz) or even anything that isn't 60Hz .

Also, a monitor may support a given mode over VGA but not over HDMI . I have not checked, OP's monitor in this case, but it is not without reason that DVI/HDMI equipped cards typically scale everything to a specific resolution/timing (which they choose from the monitor's EDID) rather than output in passthrough mode under DOS/BIOS.

EDIT : Actually, checking https://downloads.dell.com/manuals/all-produc … guide_en-us.pdf , the manual makes no distinction between input (VGA and DisplayPort) capabilities so the supported scanning ranges/modes supported should apply to all inputs. That monitor has no DVI or HDMI input, by the way, only VGA and DisplayPort .

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