Dragon 32 - Service Information (RWEW/KA/0080a)
Using a cassette recorder and lead known to work successfully with the Dragon 32, save and load a small program. If successful, then the problem is likely to be cassette-computer mismatch.
1. Check lead from computer to cassette internally for short or open circuit.
2. If MOTOR ON/OFF function is at fault, try pulling 2.5mm jack out slightly.
3. Check cassette output signal level is at least 1V positive and 0.5V negative with respect to ground.
4. To limit signal from cassette to computer, fit resistor (270-470R) in series with cassette input. This can be done by cutting the track to Pin 4 of the tape socket and bridging with the resistor.
5. Check that recorder does not distort waveform (i.e. worn or dirty lead).
6. Remove Mic lead when loading and Ear lead when saving.
7. Do not have TV too close to computer.
If the problem appears to be with the computer:
1. Check relay operation and diode D1 2. Change IC20.
3. Change IC25. 4. Change IC34.
Problems can also be experienced using cassette recorders fitted with ALC (Automatic Level Control) due to the response time of the circuit. This can usually be overcome by using the following program to save programs in memory. The cassette recorder should be set up to record and the following entered as one line:
MOTOR ON: SOUND 120;50 : FOR N = 1 TO 100 : NEXT: CSAVE "Program Name"
This has the effect of allowing the ALC to settle down prior to the output of data from the computer.