This begins a series of articles on how to repair the problems’ that spring up with your ZX81 and TS1000. Sending off to have your computer repaired can cost as much as–if not more than–the original cost of the computer. The majority of the problems can be fixed by the average owner.
The first problem that I will cover is LOADing and SAVEing. If the computer works otherwise, 99% of LOADing/SAVEing problems lie in the cassette recorder you are using. The ZX/TS machines have one of the poorest (and slowest) ways of loading a program. You have no idea whether the program is actually loading or just passing what it thinks is garbage.
Most problems are caused by not having the proper volume setting while loading. One of the best ways of telling whether the program is loading or not is by watching the TV screen. The proper volume setting can be determined by watching the black and white lines on the screen during the more “steady scenes”. The black lines should be slightly thicken than the white lines in between. On some sets with bad linearity, the lines may appear to get thinner towards the bottom of the screen (the display appears to be smaller towards the bottom as well). On these sets, try to watch the top few lines to make the black lines thicker than the white ones. That should give you proper volume for loading (typically around 3/4 of maximum volume).
The type of recorder is very important. Use only a standard type monaural recorder. Don’t use stereo portables, home type units or micro-cassettes, they probably will not work. Your best bet is to use a good quality desk-top recorder which includes a tone control, tape counter, and its own power supply (generally in the $35 to $50 range). We have found that Panasonic recorders work with good results. Timex’s works well and now Sears has a model out that looks identical to the Timex 2020 recorder.
Don’t use a recorder from the closet that has been sitting collecting dust–it probably won’t work. Have the recorder cleaned and belts replaced first before trying it. After sitting so long, the belts develop flat spots and cause an uneven speed, and dust can gum up the mechanism and cause the machine to eat your new tape. A recorder in good condition is a must.
Tone is another important factor to consider. If you have a tone control, be sure and place it in the highest position possible. If after trying all this and it still won’t load, disconnect the earphone jack and turn the volume down to a tolerable level and listen to a pre-recorded professional program. If it sounds dull and muffled, the head azimuth may be off or the heads dirty. Head azimuth is the angle of the tape data track with respect to the pickup on the head (should be parallel: zero degrees). For dirty heads, take cotton swabs and rubbing alcohol and gently clean the heads so that they appear shiney. If the heads are not dirty, the head azimuth should be adjusted.
A lot of tape recorders have a small hole right above the audio head (front center of cassette basket) which reveals a screw while in the play position. Play the tape and use a jeweler’s screwdriver to turn the screw. You should hear the “muffledness” change. Adjust for the most “shrill” sound possible (produces the most highs). If you don’t have a head azimuth adjust hole, take it to a service center and have it done.
You should be able to now load without any problems. If not, play a tape and see if you hear any wavering or a stop and go type of sound. If you do, have it serviced, or buy another recorder (the motor may be going). If it sounds fine, then check all your connections, try another tape, have only the ear plug connected for loading and the mic plug connected for saving (remember, its ear to ear and mic to mic). If problems still persist, try another recorder on your computer or your recorder on another computer and ascertain which is the problem.
Once you have the loading of a prerecorded tape down, saving should also work. After you save a program, play it back with the mic plug out and make sure that something went onto the tape. If not, check your connections, and/or try another recorder. If playback of a pre-recorded tape is fine but playback of your recorded tape is muffled, have the heads demagnetized and cleaned.
Everything in this particular article also pertains to the 2068. Although loading problems do not occur as frequently, they still do occur with the color computer. Head azimuth is a little more critical due to the faster transfer of data. Tapes come to you with varying levels of quality and may have been recorded on a recorder with head azimuth slightly different than yours. Some hard to load tapes can be loaded by adjusting the head azimuth slightly.
Finally, use a good quality tape (not the three for $1 specials). And on the TS1000 make sure you are not trying to load a 16K program into a 2K RAM.