During the hot summer months, store your ZX printer aluminum printouts in a dry place. My program printouts developed black spots when kept in a humid basement, making them unreadable.
Richard Bryan, Falmouth, MA
I discovered an easy fix to an annoying problem. One of my ZX81 keyboard’s foil tracks broke between the keyboard and its connector; a likely consequence of some recent modifications to my computer. Using the schematic in SQ (Winter82 p.47) I located the bad track, and replaced the missing section with aluminum foil. First, I placed some tape on the foil to provide enough stability when trimming. I taped this foil bridge over the defective track with plenty of overlap on the good portion of the conductor.
My keyboard works like new, and I saved myself the hassle of a repair charge.
Ken Hartgrove, Miami, FL
Do you know of any products to reduce or eliminate interference? My video display wavers when cars drive past, or when someone runs a large appliance.
Myron Felckowski, Stevens Point, WI
Any number of things could fix this problem. Try separating your components, buying power backup supplies (SYNTAX Jul.83 p.7), using a different TV, or hooking up a monitor instead of a TV.–KO
Operating manuals for the CAI Interface Module and ESF Stringy Floppy indicate that the 8K-16K memory locations must be available for the system. It works fine with my 16K Sinclair RAM module, but not with my JRS 64K RAM pack. Do you know of some way to modify my JRS to open up the 8K-16K area?
Jim Alderson, Santa Paula, CA
Prevent the RAM CS from selecting the memory in these address spaces. See the decoding description for 64K RAM packs in SQ Summer 83.–KO
Three other ZX/TS owners and I discovered an unusual way to solve our LOADing problems. When replacing all four tape recorder batteries failed to fix bad LOADs in my ZX81 kit, I used two new and two weak batteries in my GE tape recorder. I have done this for a year with no problems–whenever the batteries need changing, I leave the two most recent batteries in and add two new ones.
My three friends use TS1000s and Panasonic or Sony tape decks, with similar results.
Paul G. Allain, Gardner, MA
If you run the recorder from an adjustable DC supply, you’ll find a range of voltages over which it operates well. You can then build a fixed regulated supply whose voltage equals the square root of the product of the maximum and minimum voltages at which the machine loads.–KO
Hardware tip: The pin jacks for power, mic and earphone contain very weak springs, sometimes causing you to lose programs just from touching the power cable. I unsoldered the jacks and replaced them with better ones from Radio Shack–ordinary panel jacks. Although I had some difficulty wrapping a wire around them to solder to ground and solder the tab into the circuit, this solution works. Result–not one power loss in a year, and I can pick it up or shake it without fear of lost programs.
Robert Jenkins, Chicago Heights, IL
After attempting to perform some of the floating point examples given in Toni Baker‘s book How to Program the ZX81 in Machine Language, I realized that some of the call addresses given for various floating point routines in the ROM are incorrect for my ZX81. Can you explain this?
Michael Stokes, Tullahoma, TN
ZX81s built before late 1981 contained ROM bugs. When correcting the problem, Sinclair offset all code in the new ROM by three bytes after 0EEFh, See SYNTAX (Nov.81 p.7) for the newer 8K ROM map. We know no errors in Toni’s book. Anyone else?–AZ
Do you know of an interface to connect my ZX81 to the MPI (Micro Peripherals Inc.) Mod. 51/52 Flexible Disc Drive with 500K storage? It’s designed to run with computers such as those from IBM, Texas Instruments, or Radio Shack, which have their own power supply and I/O cable terminating in 34-pin PCBA edge connectors.
Harry D. Graham, Kingston, NY
Aerco sells the products you need: FD-FX Floppy Disk Interface (plug-in) for $179, and DP-2 power supply for $79. The power supply provides the needed voltage for each drive of 5V at 1-1/2 Amps and 12V at 2 Amps. Aerco, POB 18093, Austin, TX 78760, 512/385-7405.–LFV
I have two 16K RAM modules (one is a TS1016) that can’t piggyback to form 32K. How can I combine the two to get more memory?
David Pinto, Jensen Beach, FL
You must perform some hardware mods to merge your RAMs. While we can’t detail a complete solution, we can tell you that a RAM pack knows its address by the way address lines and RAM CS are connected. If you arrange to divert RAM CS from one RAM pack to the other, you cause the first to be active between 16K and 32K and the second to function from 32K to 48K. See SYNTAX (May82 p.5) for circuit hints.–KO
Can you POKE new lines into a program without BREAKing and LISTing the new line number? I can find the address after any program line number by PEEKing 16425, but attempts to POKE into addresses after those holding the last character in the line causes a crash or POKES characters onto a blank screen. Any ideas?
Tim Lichtenwald, San Francisco, CA
Ideas yes, methods no. We made a quick pass at POKEing to the edit file, but that didn’t work. You could create a bank of REM statements with sufficient room to hold new names, then automatically POKE them to active statements. You’ll find the basic method for changing commands in SYNTAX (Feb.81 p.12), but now you have a more complex address-finding scheme to develop. We know the ROM contains a routine to insert BASIC lines, but we don’t know how to use it. If any reader can help us, we’d be grateful.–KO
How can I convert the English ZX Spectrum to US television standards? Neither Timex, Sinclair, or Ferranti carry the part I need (Ferranti ULA #114, or equivalent). Can you help?
Rick Barnett, Woodbridge, VA
We know of no additional sources, but you can run your Spectrum in black and white on many US TVs. Also, you can buy a PAL-standard TV or monitor that can accept various color standards like the $600 JVC TM-14PSN. For the monitor, you must also use direct video just as you would for a ZX/TS.–KO