ogma
Newbie
Posts: 34
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Post by ogma on Nov 17, 2009 14:52:01 GMT -5
I won a lot of Sinclair stuff off eBay yesterday and the lot includes a 1500 that appears to have been slightly modified. Anyone have any ideas about what might have been done here? I'll know first-hand when it arrives in a few days, but until then...
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Post by retrobits on Nov 17, 2009 15:57:23 GMT -5
Hmm, I posted a thought, but then decided to Google the part shown on the back. The "Astec" part is an RF modulator. I wonder if the internal RF modulator wasn't working, and they hot-wired this one on the back to fix it?
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ogma
Newbie
Posts: 34
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Post by ogma on Nov 17, 2009 17:13:56 GMT -5
That was my impression, as well.
Well, I'll know soon enough and I'll let you all know!
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dilbert
Full Member
Registered Linux User #306113
Posts: 223
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Post by dilbert on Nov 26, 2009 19:07:58 GMT -5
Hmm, I posted a thought, but then decided to Google the part shown on the back. The "Astec" part is an RF modulator. I wonder if the internal RF modulator wasn't working, and they hot-wired this one on the back to fix it? I agree with Earl. dilbert
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zeem
Junior Member
Posts: 82
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Post by zeem on Jan 7, 2010 15:49:55 GMT -5
The UM1233 is a UHF modulator, usually outputting on channel E36, which would normally be used for PAL. If you look at the side of the unit that the output socket's on, it doesn't line up with the hole in the case, because the VHF modulators have them on the other side. Look at the side of a ZX81 and you can see the moulding marks in the plastic where the other hole might be on a machine with the other video system.
I'm guessing that someone's converted this for use with a UHF TV and didn't want to chop a hole in the case. One way to tidy this up and make it more useful is to remove the UM1233 and its power supply wire, and replace it with an inline RCA socket. This should give a straight composite video output, and is a common 'upgrade' on ZX81s and particularly Spectrums, because of the improved picture quality it gives on modern TVs.
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