Spectrum tape loading notes

Loading games from tape on the 16/48K Spectrum:

On the Spectrum (and other 8 bit machines) loading from tape was always a hit-and-miss affair, even back in the day. A wide variety of tape decks, duplication methods and custom loading systems were used creating many variables.  Now, with the added toll of 30+ years of ageing on these electro-mechanical devices, things are even worse.

With the Spectrum 16/48 we do have the “luxury” of some adjustment via the volume control – and sometimes tone control – of the tape deck’s output. (On the C64 and Spectrum 128+2 twiddling with the azimuth tape head alignment screw is about the only option). Always use a mono audio cable (such as the original Sinclair EAR+MIC cable) as stereo cables can reduce the volume.

On the tape deck side, bear in mind many old players from the ’80s will now be in a poor state. First, make sure the tape head is clean (use isopropyl alcohol on a cotton bud). If the player stuggles to play C90s (for example midway through the tape) the drive belt is most likely worn and should be replaced. The head alignment azimuth screw can usually be adjusted if a hole is provided to access it, but beware this can open a can of worms: A good setting for one game may throw it out for many others! (Some computer-orientated cassette decks from back in the day are known to be reliable loaders even today, for example the Saisho DR10 and similar units sold by Boots and WH Smith.) If a cassette deck chews tapes, check for dirt and debris on the pinch roller and capstan pin – these can also be cleaned with isopropyl alcohol.

Sometimes the cassette tape itself will just have deteriorated. If you play it out load and can hear fading, hiss, pops or other unwanted noise then no amount of twiddling will fix it. (It’s possible a fresh image of a game could be saved over the top, but often it’ll just be a goner.)

Spectrum-side specifics: If you have an early Spectrum, it’ll probably have an issue Issue 2 board with 5Cxxx ULA chip. These usually require a fair bit more volume to successfully load even with a pure source, IE: A .wav played from a PC. (For example, using my PC’s speakers’ headphone socket, the volume has to be 75% for issue 2 Spectrum boards but is fine around 50% for issue 3 and above. Laptops and MP3 players often struggle to provide enough volume on any Spectrum – you may get the header loading bars but the Spectrum fails to pick up data, ie: No “Program: Game” report, or the dreaded R-Tape Loading Error). So, if your tape deck is at maximum volume just to get a particular game to load, its very likely others will not.

Other things to check:

Make sure the EAR socket is OK. It shouldn’t crackle / drop out or change volume if you touch the jack plug lightly during loading. You can try cleaning it with isopropyl alcohol on  a cotton bud, or by just repeatedly inserting and removing a jack plug. But if it is loose, the socket should be replaced. (I sell these at my retro store).

Is the speaker OK? If it has low impedance (much below 200 ohms for issue 2 boards and 40 ohms for issue 3+ boards) it can pull the EAR input down.

No loading lines at all strongly suggests either the source volume level is way too low or there’s a diode D13 or ULA fault (if the BEEP command is working then diode D9 should be OK, but check it for closed circuit). There are a few passive components in the MIC/EAR system, but mainly it’s diode D13 and the ULA that affect the input level. (During loading routines, a bias voltage has to be generated by the ULA – if this is not present then the Spectrum will be not detect the sound input.)

Swap the ULA (IC1) with one from another Spectrum (you can put any version ULA in an issue 2 board, preferably the same as fitted already, but issue 3 and above boards should only have an 6c001E-6 or 6c001E-7) If loading improves then the ULA has gone a bit deaf (as happens with old age:)

If playing wav or .tap files from a PC, it’s possible its soundcard just does not provide a pure enough signal or the output can’t get  loud enough for a Spectrum. Some modern PC speakers fix or limit the volume level to their headphone jacks.