VRW  PUBLICATIONS          HOME   |   BOOKS  |   SERVICE DATA   |   RESTORATION   |   RADIO HISTORY

 

BUSH DAC90A RESTORATION  

WOOD  BAKELITE  CHASSIS  ETHICS  DIODE, TRIODE  TETRODE, PENTODE  STANDARDS PHOTOGUIDE  VIDEOS

PILOT  BUSH  EKCO  COSSOR  PHILCO  BAKELITE HISTORY VALVES DIODE, TRIODE  TETRODE, PENTODE  STANDARDS

 

The Bush DAC90A has established itself as a firm favourite among collectors. There are many of these still around and a good example may be obtained without breaking the bank, though in most cases considerable restoration is advisable. 

It should be borne in mind that the set is live chassis, being AC/DC technology. There is no isolating transformer to give a measure of protection. There is also a metal grille mesh. Ensure this cannot be in contact with the chassis. The mains connector - a 2 pin affair - can be connected with equal ease either way around, so that in itself is a cause for concern. I tend to dispose of the connector and fit a permanent twin-core flex. 

However well the restorations and modifications are done, the set cannot pass today's stringent double-insulated safety tests.

During restoration: Replace the waxy capacitors and especially the one across the mains input - a 'Y' safety rated capacitor should be fitted here -  and the one across the sound output transformer primary. The UL41 output valve is one major let-down in this otherwise reliable set as it tends to develop a heater-cathode leak, resulting in hum on the sound. Also, unfortunately, the output transformer is prone to failure, especially if the valve is faulty.

Before replacing a valve, check and almost certainly replace the capacitor that is the control grid coupler as this too is prone to failure, causing a positive potential to be applied to the grid, the result of which severely shortens the life of the valve. New old-stock valves are becoming rare and therefore pricey. It is possible though a somewhat fiddly task to replace the UL41 with a different valve. This involves a change of holder and an adjustment in value of certain components. Transformers can be rewound or replaced with salvaged components. The mains RF bypass capacitor should be replaced with one of a suitably high voltage working and a 'Y' rating for safety. Often, the original component will be found to have exploded.

A restored set will provide good no-frills performance on medium and long waves.

Bush DAC90A in cream Bakelite

The whiteish cream case (actually Urea Formaldehyde) is not quite as strong as 'genuine' Bakelite and tends to stress crack spontaneously. Perhaps this is the reason why fault-free examples fetch rather higher prices than the brown versions. The chassis is identical to the brown versions. An excellent performer on both bands.

 

PILOT  BUSH  EKCO  COSSOR  PHILCO

 

 

VINTAGE RADIO world: SIXTEEN YEARS OF WEB PRESENCE