1084s-D2 (analog only variant) - RGBI/TTL adapters?

[2mg]

This post also applies to getting C128 RGBI and MDA/CGA/EGA to work on CRT TVs.

I'm looking at 4 adapters to achieve this (I don't know if linking to shops is allowed, I'll just post names):
- CGA2RGBv2
- C128 RGBi to RGBa adapter
- CGA2SCART PRO
- MCE-adapter

However, none of these specify sync voltages, some don't mention the polarity, some don't mention sync type.

OTOH most seem to have XX khz in > XX khz out, and according to https://www.dosdays.co.uk/topics/15khz_monitors.php only CGA is 15khz (and I presume only in 320x200 mode?).

1084s-D2 (and P2 AFAIK) is a 15khz only analog monitor, and most common CRT TVs are too plus they don't usually expect TTL level sync.
I've read that GBS scalers also expect 3.3V sync as input.

I know there's a TTL mod for that monitor, but let's keep that for maybe later.

Does anyone have any experience with these, especially with "it fried mine", or should I look for something different?

 

[maxtherabbit]

Most (all?) actual computers which output 15kHz RGB used TTL sync. I would assume any monitor intended to be used with computers would be TTL sync tolerant regardless of whether the color signals are TTL or analog. You could always try to pull the schematic of the monitor and look at the sync input stage to be sure

 

[2mg]

Most (all?) actual computers which output 15kHz RGB used TTL sync. I would assume any monitor intended to be used with computers would be TTL sync tolerant regardless of whether the color signals are TTL or analog. You could always try to pull the schematic of the monitor and look at the sync input stage to be sure

Yeah that's kinda a problem if you have access to different CRT tech (multi/non-multisync monitors, 15khz monitors with or without TTL, VGA monitors, household TVs, PVM/BVMs...), especially if you can't find anything about a model online.
And I still would have to measure output sync voltages (meaning getting an oscilloscope) from these adapters since they didn't specify the sync voltage.

MCE-adapter even has a owner's self-reported issue with sync voltages, or rather the range of voltages possible and what the adapter is configured for.

But that's only the sync part, I still don't get if any of these adapters can do for example MDA which is RGBI 18khz into RGB 15khz.
And I'd really like not to find out by "plug it in, see what happens".

 

[michaelbrown91]

This post also applies to getting C128 RGBI and MDA/CGA/EGA to work on CRT TVs.

I'm looking at 4 adapters to achieve this (I don't know if linking to shops is allowed, I'll just post names):
- CGA2RGBv2
- C128 RGBi to RGBa adapter
- CGA2SCART PRO
- MCE-adapter

However, none of these specify sync voltages, some don't mention the polarity, some don't mention sync type.

OTOH most seem to have XX khz in > XX khz out, and according to https://www.dosdays.co.uk/topics/15khz_monitors.php fnf only CGA is 15khz (and I presume only in 320x200 mode?).

1084s-D2 (and P2 AFAIK) is a 15khz only analog monitor, and most common CRT TVs are too plus they don't usually expect TTL level sync.
I've read that GBS scalers also expect 3.3V sync as input.

I know there's a TTL mod for that monitor, but let's keep that for maybe later.

Does anyone have any experience with these, especially with "it fried mine", or should I look for something different?

If your target is a 15 kHz CRT TV, I would focus on an adapter that clearly specifies 15 kHz RGB with proper sync level conversion rather than a scaler that changes horizontal frequency. It may also be safer to add a simple sync attenuation or buffer stage to avoid feeding full TTL directly into a TV that expects lower voltage composite sync.

 

[2mg]

If your target is a 15 kHz CRT TV, I would focus on an adapter that clearly specifies 15 kHz RGB with proper sync level conversion rather than a scaler that changes horizontal frequency. It may also be safer to add a simple sync attenuation or buffer stage to avoid feeding full TTL directly into a TV that expects lower voltage composite sync.

If your target is a 15 kHz CRT TV:
My target currently is that specific 1084S-D2, which is only 15khz indeed.
Also, it's TTL Sync + analog RGB via DE9 , as it was made for the Amiga.

I would focus on an adapter that clearly specifies 15 kHz RGB with proper sync level conversion rather than a scaler that changes horizontal frequency:
Those devices I linked aren't scalers (unless they're XYZ to VGA), they seem to be transcoders.
Issue is is that output sync level and polarity is not really known, and what happens if you send a non-15khz signal to a 15khz monitor.
Do you know of any that only do that one job?

It may also be safer to add a simple sync attenuation or buffer stage to avoid feeding full TTL directly into a TV:
Isn't putting 470ohm resistor enough to bring down TTL Sync (5V) down to TV/Video levels?
I'm unfamiliar with what buffering is, can you please explain in short?

 

[Eudimorphodon]

CGA2RGBv2

That’s the GGlabs thing built using a GAL as a DAC, right? I have hand-built a similar device on breadboards to use for various experiments and it works fine, the RGB conversion through a resistor ladder is not rocket science…

Anyway. Regarding sync levels, I’m 90% sure an Amiga, which is what a 1084 is designed to work with, outputs TTL C-Sync, which is the same as accepted by arcade scaler boards like those cheap GBS-8200s they sell on Amazon. I do *not* think a 1084 needs 75 ohm terminated sync like a SCART TV.

 

[2mg]

That’s the GGlabs thing built using a GAL as a DAC, right? I have hand-built a similar device on breadboards to use for various experiments and it works fine, the RGB conversion through a resistor ladder is not rocket science…

Anyway. Regarding sync levels, I’m 90% sure an Amiga, which is what a 1084 is designed to work with, outputs TTL C-Sync, which is the same as accepted by arcade scaler boards like those cheap GBS-8200s they sell on Amazon. I do *not* think a 1084 needs 75 ohm terminated sync like a SCART TV.

I've been told CGA2SCART PRO does the same, unsure about it's sync output tho since it's a "to SCART", tho if it's to video levels (1Vpp) it wouldn't probably harm the 1084, but I'd prolly get a garbled image.

Problem is what happens to a 1084 if you feed it outside 15khz - a garbled image or a fried box?

 

[Eudimorphodon]

Problem is what happens to a 1084 if you feed it outside 15khz - a garbled image or a fried box?

It will probably lose sync before frying, most monitors will. Frying a monitor is mostly restricted to things like early MDA monitors that don’t actually have a full sync circuit, they use the Hsync input as a direct horizontal drive.

So… why are you worried about that? Are you intending to feed it out of range signals?

 

[2mg]

It will probably lose sync before frying, most monitors will. Frying a monitor is mostly restricted to things like early MDA monitors that don’t actually have a full sync circuit, they use the Hsync input as a direct horizontal drive.

So… why are you worried about that? Are you intending to feed it out of range signals?

Well since my 1084 hasn't TTL RGBI, I thought of getting one of those adapters, to kinda make it like fully-fledged 1084.
Seems simpler and safer than internally modding it for RGBI.

That would allow me to use some IBM modes like CGA, and C128's 80 column mode, tho I've yet to obtain something IBM (unless a Raspberry Pi can do all IBM modes via IO pins/hats, have to test that too).
But in case I do something wrong, ala pick the wrong mode or random software switches it automatically from whatever device I plug into that adapter, I'd just like to have a peace of mind that it won't fry the 1084.

PS: I'm finding conflicting info on IBM modes regarding kHz, is there a definitive chart somewhere, especially if it includes Hercules mode info?