BUSH DAC 90A RESTORATION
One of my most recent restorations was the refurbishment of a British made Bush DAC 90A Medium/Long wave radio from the 1950's. The DAC 90A radio was introduced in 1950. This model superseded the DAC90 and uses smaller valves and a completely redesigned chassis. It is a five valve super-heterodyne receiver with a well laid out chassis housed in a beautiful Bakelite cabinet. It is an excellent candidate for restoration as it is well laid out and easy to get to all of the components. The restoration consisted of:
- Replacement of the UL41 audio amplifier valve (V4) which was causing a loud distorted hum, a common fault
- Replacement of the UF41 RF stage amplifier (V3) which had reduced output
- Replace valve 3's faulty valve base which was making bad contact
- Replaced the 460K resistor in the audio amplifier stage which had gone high resistance (600K+)
- Removed components from pin 4 of V3
- Replaced all wax coated paper capacitors with modern equivalents (re-capping).
- Replaced power supply smoothing capacitors C20 and C21 with modern equivalents
- New mains cable as the old one was broken and dangerous
- Removed all dirt and grime from the radio chassis and speaker grill
- Cleaned and polished the Bakelite case.
The MW and LW radio bands are rapidly being abandoned by more and more radio stations in favour of FM, DAB/2 or Internet transmission. Even FM is being abandoned in favour of DAB/2. This means that the choice of radio stations for listening on MW/LW is very limited. However the Raspberry Pi Internet Radio project shows how a Vintage Radio can be interfaced to Internet Radio streams allowing almost unlimited access to radio stations over the whole world or even playing music from a USB stick or network share. Below is a photo of a low powered (1 milli-watt) AM transmitter which can connect to any audio output to the transmitter with a standard jack plug. See the Internet Radio Vintage Supplement for further information