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I recently won a 48K Spectrum on ebay (with a LO Profile keyboard ) Its nice to have a spectrum again after all these years (I'm 39 by the way..)
I would like to know if it is possible to use a VGA monitor with the 48 in any way?
Has anyone had any success with this?
Does the GBS8200 work?
Any help appreciated, Thanks.
Getting standard RGB (SCART) signal is tricky already; to get a valid VGA output you also need to adapt the scan frequency and generate few more signals, they seem to be doing it here:
* Some circuit to take composite sync (in the Y signal?) from the ULA, and pull separate horizontal + vertical syncs from it. Such circuits exist (LM1881 for example), but how to wire those into a Spectrum 48K...??
* Some circuit to convert color signals from the ULA (= some flavor of YUV) into RGB.
* VGA monitor that can handle ~15 kHz horizontal sync. Such monitors exist, but which ones? I've never seen a good list.
* Wiring up all of the above.
In other words: lots of work including some circuit design, with uncertain outcome. Instead, I'd choose between 1 of 2 routes:
1) Find a Spectrum 128K or later model, and use with a monitor/TV that has a SCART input. Or:
2) Use any monitor/TV that includes a composite video input (apparently even some VGA monitors have this!). Such a monitor would surely have to support the horizontal sync frequencies that are common for devices with composite video output.
Hint: in case you lack a 128K or later model: these tend to be expensive, and chances are you can buy a looooottt of monitor for the same money.
The composite mod consists of removing the 5v power to the RF module, desoldering the resistor connected to the back of the RCA connector and feeding the input to the RF modulator straight to the centre pin of the RCA connector.