More faults with recent Ferguson machines. We’ve had three cases in as many weeks of the VCR -TV lead being faulty, something we’ve not had trouble with before. Here’s a common problem with the 3V29/3V30. If the symptom is no or intermittent colour and the fault seems to disappear when the bottom is removed, check that capacitor C487, which is mounted under the bottom board adjacent to R417, is not shorting to the bottom plate when this is fitted.
No clock display on one of these machines was traced to the filament current generator transistor Q403 being inserted in the print but not soldered. No vision on record but playback o.k. was traced to one end of C294 being dry jointed. In another case the machine would lace up then switch off, due to failure of the capstan motor to start. On checking the outputs from the mechacon/function board to the servo board we found that a pause signal was being sent through though the pause button was not pressed. This signal originates from pin 22 of IC4. The output here was correct, as was the output from the following inverter (part of IC6). This output passes via zener diode D23 to the base of transistor Q17, but due to a print fault (not a crack) the diode and the inverter were not linked. So much for production/quality control faults. We’ve also had a couple of component failures recently. The fault with a 3V30 was no signals in the E -to -E mode due to failure of transistor Q4 on the tuner/i.f. board.
On another of these machines there was no battery back-up (the clock is supposed to keep the correct time and the memory to retain the programme in the event of mains failure). The fault was traced to a component marked CP1: it’s in series with the supply to the stand-by circuit and was open-circuit. When a circuit came through we found that this stands for Circuit Protection device – a glorified fuse I suppose.
A problem we get in certain areas of Birmingham is radar interference from the airport. In the past this has usually been confined to Hitachi machines and has been cured by tuning the u.h.f. modulator down towards channel 30. The 3V29/3V30 seem to be even more sensitive to this and tuning down often fails to provide a cure. In this event an attenuator (in one case 18dB) has to be fitted.