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Sinclair ZX81

F

fred3rd

Experienced Member
Joined
Apr 29, 2006
Messages
213
Location
Central Pennsylvania U.S.A.
myZX81sm.jpg


Gentleman I'm looking for some help with my Latest project, a Sinclair ZX81, AKA the Timex Sinclair T1000. I installed a jack to connect a composite monitor using the directions outlined at the following website. http://www.mainbyte.com/ts1000/composite.html After completing the modificatiom, (top left in picture) I hooked it up to an Apple Monitor II. I am getting no display. I should get a cursor. Has anyone else attempted this modification?

Is it possible this monitor is wrong? Anyone, Anyone, help?
 
Seems like it should work, from the schematic shown, but, the instructions don't make it clear that you should solder the braid from the co-ax to the ground lug of the RCA connector and to a ground point in the computer.

Otherwise, you have no signal return or ground reference.
 
I just got home from my storage facility that I rent to store my puter stuff in. I Rooted around until I found my pile of Apple A2M2010 green phosphor monitors. I brought one of them home and tried it. I still don't get anything of a picture (cursor ect). The screne does flicker when I press one of the command keys though. Back to square one with my head in my hands. Hmm :(
 
Did the tv picture show up with the "k" all the time before the mod? I just got a 1000 off of ebay, it only manages the correct screen about 1/10th of the time. I have to keep powering it off and on until I get a nonblank screen (well, totally white one actually). Buying another one today, first one likely going in the trash or used for parts.
 
Unfortunately I don't have a compatible TV with UHF. This is my second one off ebay. The first one has both kb ribbons broke. So far I have about $100 in 2 ZX81's w/16 k plus books, printer, and a tape drive. I never had this bad of luck. Are these things possessed?
 
Hey, "broken keyboard cable" is one of the things wrong with my first one also. I took some scissors and trimmed the cables square again and attempted to stuff them back into the connectors. Keyboard would "sort of" work, a lot of the keys in the middle of the keyboard still don't work. Obviously, my trim trick didn't work. I might end up with 3 more of them (chuckle). Have a few low bids out there.
 
ZX81 Resolution

ZX81 Resolution

:D Ok, I figured it out. In the pics @ http://www.mainbyte.com/ts1000/composite.html figure 2 and 3 are a little conflicting. Figure 2, a schematic, depicts U.S.A. as being the center of three legs coming off the modulator. That's what I went by, WRONG! The picture in figure 3 is actually more correct, although harder to see. Of the three legs, the correct one is one of the outside legs closest to the outside of the board on that side. Hooked up as such, my ZX81 works on both the Apple Monitor II and the Apple model A2M2010 green phosphor monitors. I hope this is as helpful to others as it was to me when I figured it out.:D
 
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