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Old 20th Aug 2018, 8:59 am   #1
onextwo
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Default Marconi 2955 LCD?

Hi,

Has anyone tried replace the CRT with a LCD in a Marconi 2955?

Or will it just not be possible.

Thanks Stephen
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Old 20th Aug 2018, 4:46 pm   #2
mole42uk
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Default Re: Marconi 2955 LCD?

Because of the way the CRT is driven it might be an extensive mod. I'll think about it some more when I'm home and have the service manual in front of me.
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Old 20th Aug 2018, 5:00 pm   #3
Biggles
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Default Re: Marconi 2955 LCD?

I seem to remember the later test set 2945? had an LCD display. I would think trying to convert to LCD might be a problem unless you can somehow break into the video drive and then connect this to an alternative display with a composite input. Something is telling me that the video drive is not that straightforward. Without the manual in front of me I couldn't say. Remember that the LOPT/CRT board supplies some other parts of the machine with power so if you have a blown up board (used to be a common fault) the LCD conversion wouldn't necessarily provide a fix. There has been a bit of input on the forum over the years regarding the 2955 so it may be worth doing a search. I believe there is MI group on the web somewhere too but I have never looked at it.
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Old 20th Aug 2018, 6:35 pm   #4
onextwo
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Default Re: Marconi 2955 LCD?

Looking at the Service Manual the LOPT does not seem supply any other PCB.

The VDU Board puts out Line Sync / Frame Sync / Video.

So I thought I might be possible.
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Old 20th Aug 2018, 9:20 pm   #5
Biggles
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Default Re: Marconi 2955 LCD?

Ok, my mistake. It's been a while since I looked at the manual. Composite video makes things easier, unless you can find a professional monitor type LCD with maybe separate line/field/video inputs. It may be possible to combine the outputs and then feed a standard LCD monitor with the resultant composite signal. I'm not sure if the line and frame rates are standard. I have repaired a few 2955's in the past but most faults have been attributed to either the OM345 chips or the LOPT destroying itself. There used to be a mod kit out to repair/upgrade the CRT driver board but that's quite a few years back now.
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Old 20th Aug 2018, 9:46 pm   #6
McMurdo
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Default Re: Marconi 2955 LCD?

RDS do lcd panels and matching drive pcbs. Depending on the model the boards will auto-scale and sync to more or less any input, so long as you know what the signals are to start with. Worth a try.

https://www.review-displays.co.uk/
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Old 15th Oct 2018, 3:11 pm   #7
LARRY1962
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Default Re: Marconi 2955 LCD?

Note that the tube is scanned vertically, starting at the top left-hand corner, which is unusual.
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Old 25th Oct 2018, 12:03 pm   #8
Paul76UK
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Default Re: Marconi 2955 LCD?

Has anyone considered using NewScope LCD screens and interfaces for Marconi equipment? I have one in my HP 8757 Scalar Analyzer. I emailed NewScope about using their products in Marconi equipment but they didn't have any experience with Marconi and I haven't had a chance to investigate it for myself yet.

I'll have to see if the video signals for HP equipment are compatible with Marconi. If so, then it may be possible to use a NewScope screen.
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