Monitors

[MrClump]

I want to change my comments on the BL702a, after several weeks of use I've come to the conclusion this is not a great monitor for the Next despite initial appearances.

I started to notice strange vertical artefacts on the display, not the vertical banding you often see but more that bands on the display looked almost compressed. I wrote myself a little basic program to displayed alternate black & white pixels to see if I could adjust it out by changing the pixel clock and you cannot. At least not enough to completely eliminate it. On the Amiga, I can adjust the pixel clock enough to remove banding, but on the Next, it is just too far out for the monitor to adjust when using VGA0.

I found the only way to get enough adjustment on the monitor was to run the next in VGA mode 6 at 60hz, by which time the timings of the machine are so out of whack everything is running way too fast!

The 702 is going to get ditched, which is a pity as it's really great for the Amiga and it is a lovely compact screen with a great display. Back to the drawing board.

[dave18]

Does the monitor have settings for pixel clock and phase? By adjusting these on my dell I managed to get rid of all the pixel compression

[MrClump]

Does the monitor have settings for pixel clock and phase? By adjusting these on my dell I managed to get rid of all the pixel compression

It does, but the range of adjustment is not quite enough to completely clear up the image.

[dave18]

I had to play around for a while, just in case it helps pixel clock of 26 and phase of 86 gives me a perfect picture

[MrClump]

I had to play around for a while, just in case it helps pixel clock of 26 and phase of 86 gives me a perfect picture

Different monitor, so different timings I think.

I'm tearing my hair out with it now, I managed to get it looking great in Next mode, but then drop to 48k basic and the timing changes subtly and it's all out of whack again even though the monitor detects it as the same display.

I'm thinking I may just use HDMI, the timings may not be accurate but at least it works consistently.

[spikejohnc]

Thanks for the update Mr Clump. That's a shame, I was looking at the BL702a and it looked good. Let us know if you find any decent alternatives.

[dave18]

I think you will struggle to get a modern monitor that will handle the subtle timing differences between normal Next timings and other machine states like 48k basic. If you don't want to go down the CRT route then it is a compromise over how much the display artefacts bother you. My Dell is set up to be perfect in Next mode but has a small amount of banding in 48k mode, but I can live with it as if I'm being nostalgic and playing 48k games I'm happy to take some screen artefacts as I remember playing those over an RF connection!

[MrClump]

Thanks for the update Mr Clump. That's a shame, I was looking at the BL702a and it looked good. Let us know if you find any decent alternatives.

In my confusion of going down a rabbit hole trying to get the damn thing to work right, I fear I have misrepresented this monitor, so I should set the record straight!

My issues with the 702a are due to me also wanting to share the monitor between an Amiga 1200 and a Speccy Next. The monitor sees the Next in VGA Mode 0 as being the same device as the Amiga (I guess the timings must be very similar) and so won't store separate settings for each of them. As both the Amiga and Next need a different setup for an acceptable image this has caused me a bit of a nightmare. My workaround is to run the Next in VGA Mode 2 or above, which then causes other issues with this monitor, especially when dropping to 48k or 128k personalities, or even switching to the Amiga and then when coming back to the Next it cannot sync to the output from the Next.

If you only plan to use a Next (or an Amiga) with the 702a, then in 50hz, VGA Mode 0 with the Scandoubler off you will get pretty great results IMHO (see pic below). To help me calibrate the screen properly I wrote a little basic program that displays a grid of alternating pixels, which is ideal for getting the pixel clock and phase set correctly.

Code: Select all

  10 REM VGA calibration by MrClump
  20 FOR n=0 TO 7
  30 READ row: POKE USR "S"+n,row
  40 NEXT n
  50 DATA BIN 01010101
  60 DATA BIN 10101010
  70 DATA BIN 01010101
  80 DATA BIN 10101010
  90 DATA BIN 01010101
 100 DATA BIN 10101010
 110 DATA BIN 01010101
 120 DATA BIN 10101010
 130 FOR a=0 TO 21
 140 PRINT "SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS"
 150 NEXT a
 160 PAUSE 0

My plan is to now switch to a BenQ BL912, which has a DVI input and VGA, so will use the Next on DVI (I know that means HDMI timings, but I'm fine with that) and my Miggy on VGA.


ZX Spectrum Next with BenQ BL702a

[Spinnetti]

Looking to buy an inexpensive 17" or smaller one for the next, with a clean and minimal design as possible. This one looks good, anybody have one? I'm in the US, so 60hz. Hoping to find one that works for both Next video modes and basic 48k Speccy.