Hiwatt Custom Tape Echo

Inside the Hiwatt Custom Tape Echo

No service documents appear to exist for this machine. My email to Hiwatt in the UK was not responded to. Hiwatt did not make these machines. These appear to be rebranded VOCU VTE2000 tape delays. I did not try contacting that company, but others online appear to have, and have been denied any service documents.

That said, it is not a complicated machine. It is mostly discrete transistors, and a relatively small circuit board. Fortunately, I was able to fix it without tracing out the whole thing.

Symptoms:

1) Pinch roller engages briefly at power up, then disengages. (Therefore tape does not move.)

2) "Time" control does not work. Like a Roland Space Echo, this should control the motor speed, thus altering the delay time.

The pinch roller issue I suspected related to the "Auto Tape Run" feature these units have. There is a input level detection circuit that disengages the pinch roller when no signal is present, thus preserving tape life.

Looking at the circuit board, I noticed an odd IC: NJM2072. This is a "Signal Level Sensor System," and most likely the driver IC for the pinch roller relay. There was basically no voltage applied to this IC, a very suspicious sign. The datasheet said pin 8 is power, so I traced that to a +5V regulator (TA78L005, a "tall" TO92) that was visibly exploded. Just so happen to had one of these regulators in the bin from a previous Hiwatt Tape Echo repair (the bag was marked so). That took care of the pinch roller problem, but I still had the "Time" control problem.

The tape was running incredibly slow. No problem was seen in the tape path. I checked the voltage across the motor: 1.5V. That was a clear indication that the motor simply wasn't receiving enough power. Traced the motor wires back to two transistors in the corner of the PCB near the Input 2 jack. One had three different voltages at each terminal. The other had all the terminals near 2.5V. In-circuit testing suggested a shorted transistor. Out-of-circuit testing confirmed it. After replacing that transistor, the machine was fixed.

The above photo shows the location of the two parts I replaced, and I drew some lines to show what component in the tape transport those parts related to.