Sinclair ZX80 / ZX81 / Z88 Forums

I also suggest that line 10 has six characters after the REM because we are poking in six bytes not five. Screen shots: 970118A3-7309-4B3F-B580-00378C3EDBEC.jpeg FA70077E-FD5B-4837-95B0-1C763307EED7.jpeg F8472F3C-47D7-4A00-A9CD-31169D3F6D6D.jpeg The text in the PRINT statement in line 20 could be re...

Line 140 cannot be entered, as it will not pass the syntax checker. Remove the forward slash, then it will work.

Mark

Fig 1 has an error. Zone 3 is mislabelled as zone 1...

Mark

Slips in quietly...

...... look here ......

I’ve got a diagram somewhere, but that’s buried in a pile of notes....

Exits stage right...

Mark

Yes, a 2764, 27C64, 27128 or 27C128 type should be okay. But some wiring changes are needed because the EPROM pin out is not exactly the same as the ROM / socket pin out. There are no easy to get EPROM chips that have the same pin out as the socket. There is however a module that is pin compatible h...

This is the relevant circuitry: https://www.sinclairzxworld.com/download/file.php?id=9288&mode=view Note that I believe that diodes D7, D8 and D9 are shown the wrong way round (incorrect polarity) in this diagram. I can’t check, because I don’t have access to a TS1500. They are hard to find in the U...

I assume you used the resistance range on your multimeter? Does your multimeter have a diode test range? If yes, do the following: Get a drawing showing which pin is which (e,g, a manufacturer data sheet). For example this one . Connect the positive (red) meter lead to the base. Connect the negative...

The other chip that is very heavily involved with control of the RAM is IC27, a another custom IC. It has some of the controls for the non-contended DRAM plus does all the address line multiplexing for the Z80 for all the DRAM chips. As Tiger says, the first thing to do is to ensure that the edge-co...

Okay, that’s not good. First thing, with it powered off, disconnect the RAM pack and put to one size. Next, check the DC output plug and the cable at that end plus where the cable comes out of the PSU. A common problem is the copper wire inside the insulation breaks, but sometimes the broken ends to...

Yes, a higher output voltage is normal with anything less than full load for unregulated PSUs, and the nominal 9V DC PSUs supplied are smoothed but unregulated types.

The U.K. versions often go up to 15V or 16V when there is no load.

Mark