JVC TM-H1750C monitor

[adrm]

Hi all.

I have just gotten my hands on this monitor. Well, I have purchased it, but not actually picked it up yet.

Does anyone here have any experience with the TM-H1750?

Unfortunately, this unit does not have the component video expansion card, and they tend to be very expensive on eBay, when you can get them at all.
However, I have this "clone/remake" which the seller promises will work: https://www.ebay.co.uk/usr/linuxbot3000?ul_noapp=true
It does lack a back plate to secure it in place, but hopefully that's not a major issue.
Same question for this item: Does anyone here have any experience with these?

They are available in both SCART and BNC versions, and I'm a bit torn. I'm not terribly fond of SCART, but on the other hand all the RGB cables I have for my various (retro) computers have SCART plugs, so switching to BNC will mean extra cost and work.
Any strong view on this?

[adrm]

I have now had the chance to play around with the above setup for an hour, or so.

Initial impressions, using RGB via SCART:
Amiga in Hi-Res mode = horrible flickering of the headache inducing kind
Amiga games in lo-res modes = very nice image with vibrant colors

Gotek menu system on the Amiga, i.e. disk image selection = Flicker + hard to read text due to "scan lines"

BBC games (Mode 2, I guess) = again very nice image
BBC mode 7 = some flicker and slightly unsteady picture

My guess is that this PVM has "fast phosphor" which makes flicker more noticeable than I recall from back then, when I used monitors with more "persistent phosphor".
I must say I'm surprised at the rather poor image in the BBC's mode 7, though. I don't recall that being an issue in the past.

Edit:
I'm using quite poor quality cables and SCART plugs for both systems, since that's what I have on hand. Not sure to what extent these affect what I'm seeing.

[1024MAK]

The Beeb uses normal TV style interlace when in MODE 7. Whereas, in MODEs 0 to 6, normally it does not use normal interlace. That's why some CRT monitors / TVs will flicker slightly.

Mark

[adrm]

Ahhh, thanks.
I probably should have guessed that.

[1024MAK]

I'm using quite poor quality cables and SCART plugs for both systems, since that's what I have on hand. Not sure to what extent these affect what I'm seeing.

Very much depends on how they are wired. Ideally each red, green and blue video signal wire should be in it's own screened core in the cable. But for short cables (1 metre or less) it's not normally a problem if they are only in an overall screened cable.

But what is more important, is the sync signal and if the monitor / TV does not have manual input selection controls, that the SCART control lines have the correct voltages.

Mark

[adrm]

But what is more important, is the sync signal and if the monitor / TV does not have manual input selection controls, that the SCART control lines have the correct voltages.

The developer of the SCART RGB IO plugin module I purchased writes:
Takes analogue RGB or YPbPr input, standard 0.7Vpp signal levels, 75ohm terminated. Sync for RGB from the SCART connector can accept both the standard composite video as sync, as well as combined sync at 0.7V up to 5V levels.
(He sells both SCART and a BNC YPbPr versions of the module)

When I examine the two cables I have tested, I find the following:
BBC
Sync = 3.2V p2p --> Should be ok
RGB = 3.7V p2p --> Much too high? Resistors used on these


Amiga
Sync = 4.9V p2p --> Should also be ok?
RGB = 1.2V p2p --> 0.5V too high? No resistors, as far as I can tell

Both cables have only rudimentary shielding, and the individual leads have none, as far as I can tell. However, both are also 1m or less.

[1024MAK]

The developer of the SCART RGB IO plugin module I purchased writes:
Takes analogue RGB or YPbPr input, standard 0.7Vpp signal levels, 75ohm terminated. Sync for RGB from the SCART connector can accept both the standard composite video as sync, as well as combined sync at 0.7V up to 5V levels.
(He sells both SCART and a BNC YPbPr versions of the module)

When I examine the two cables I have tested, I find the following:
BBC
Sync = 3.2V p2p --> Should be ok
RGB = 3.7V p2p --> Much too high? Resistors used on these


Amiga
Sync = 4.9V p2p --> Should also be ok?
RGB = 1.2V p2p --> 0.5V too high? No resistors, as far as I can tell

Both cables have only rudimentary shielding, and the individual leads have none, as far as I can tell. However, both are also 1m or less.

Were the voltages you quoted taken with the leads not connected to the "SCART RGB IO plugin module" (which in turn should be connected to the monitor)?

For the BBC SCART lead: Each resistor is being used as one half of a potential divider, the other half is formed by the 75 ohm termination resistor (normally in the monitor or TV, but in your case, in the "SCART RGB IO plugin module"). This arrangement being needed as the BBC RGB outputs are designed and specified to be TTL logic levels.

The output from the Amiga may also depend on the outputs being loaded by the 75 ohm termination resistors.

Mark

[adrm]

Were the voltages you quoted taken with the leads not connected to the "SCART RGB IO plugin module" (which in turn should be connected to the monitor)?

For the BBC SCART lead: Each resistor is being used as one half of a potential divider, the other half is formed by the 75 ohm termination resistor (normally in the monitor or TV, but in your case, in the "SCART RGB IO plugin module"). This arrangement being needed as the BBC RGB outputs are designed and specified to be TTL logic levels.

The output from the Amiga may also depend on the outputs being loaded by the 75 ohm termination resistors.

Ahh, yes.
The 75 Ohm resistors were missing from the equation, i.e. cables were not connected.

[kuro68k]

Most of these professional video monitors have the flicker problem with interlaced images. I guess it was so that they showed motion more clearly for video editing and visual inspection.

Some support 24 or 31kHz but not that one unfortunately.

[adrm]

Most of these professional video monitors have the flicker problem with interlaced images. I guess it was so that they showed motion more clearly for video editing and visual inspection.

Some support 24 or 31kHz but not that one unfortunately.

Yes, I suspected as much.
"Slow phosphor" would be a disadvantage on these, presumably.

From what I can see, anything above 15KHz sync seems to be found mostly in Sony's BVM series [15khz (240p/480i), 31khz (480p), 33khz (1080i), 47khz (720p)]

I have also learned that a monitor with fewer TVLs would be better.
Oh well, you live and learn. I typically only know what information to look for, AFTER I experience the issues myself.

[alex_farlie]

I have now had the chance to play around with the above setup for an hour, or so.

Initial impressions, using RGB via SCART:
Amiga in Hi-Res mode = horrible flickering of the headache inducing kind

You need a 'Flicker fixer'. (https://en.wikipedia.org/wiki/Flicker_fixer) The flickering in Hi-res was a noted issue on some Amiga models.

[adrm]

I have now had the chance to play around with the above setup for an hour, or so.

Initial impressions, using RGB via SCART:
Amiga in Hi-Res mode = horrible flickering of the headache inducing kind

You need a 'Flicker fixer'. (https://en.wikipedia.org/wiki/Flicker_fixer) The flickering in Hi-res was a noted issue on some Amiga models.

Unfortunately, they take to signal up to 31KHz, from what I can see.
Most games work fine and flick free, so I'll stick with those for this monitor. And use my RGB to HDMI converter for other stuff.