User manual

down the Filter Tracking pot, and removing or changing the Filter CV input voltage.

Another reason for not hearing any sound is the Decay pot being fully anti-clockwise

whilst the Soft Attack pot is fully clockwise – but only for non-accented notes. Beware

too of the waveform switch being in mid-position!

Potential reliability problems

In general I have been very happy with Devil Fish reliability. The seven small pots in the

Devil Fish section are made by ALPS in Japan – the same company which makes the

original 6 pots along the top, the original Tempo and Volume pots. Despite all the

turning these pots have had in 276 Devil Fishes (September 2013), some of which are 20

years old, I have never had a report of one failing. Please don’t treat them roughly, but it

seems these are remarkably reliable pots.

The TB-303’s CPU may freeze or misbehave when operating from C-cell batteries or an

external power supply which does not provide sufficient voltage. When the sequencer is

running, the Run/Stop LED functions as a power supply voltage indicator. The voltage

sensitivity is provided by a separate circuit and is not altered by installing different colour

LEDs. The Run/Stop LED should be on brightly, or perhaps just dimming a little when

more current is drawn by the Devil Fish LEDs. If it is dim, then the batteries or external

supply are not providing enough voltage, and you cannot expect the CPU to function

correctly. Failure may involve cessation of sequencing and front panel activity until the

machine is turned off and then on again. Failure may also include playing patterns in an

erratic manner, problems writing patterns, playing patterns but not driving the Gate (so

there is no sound) etc. Please see the section above on operation from C-cell batteries.

CV In socket: internal sequencer CV or MIDI In control misbehaving

An occasional problem is that the internal sequencer does not drive the Devil Fish

oscillator and Filter Tracking correctly. (Likewise, the CV Out socket will not respond as

it should to the internal sequencer.) With the MIDI In system, the same applies, since the

internal sequence and MIDI In system both drive the Digital to Analogue Converter,

which goes via switch contacts in the CV In socket to the Slide circuit.

There may be no pitch variation or an incorrect variation. Sometimes the VCO pitch

warbles slightly. The cause is the rear-panel external CV In 3.5mm socket. This socket’s

tip contact also functions as a switch to another contact in the socket so that the internal

sequencer’s CV (or the CV produced in response to MIDI In) is used when no plug is

inserted. This connection between the contacts is metal-to-metal and so should be

perfectly reliable. However, it seems that it is possible for the connection to fail or to be

flaky.

When this happens, there is no evidence that dust, liquids or misuse were problems.

The problem does not necessarily arise due to use of these sockets.

Fortunately, the problem can be fixed simply by inserting a plug into the CV In socket

and removing it. This may need to be done a few times before the contact area is freed of

whatever contaminants were causing the trouble. If this doesn’t work, try twisting the

plug clockwise and anti-clockwise as you slowly press it into the socket. This will cause

the spring contact to move sideways against the fixed contact.