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
A restored set will provide good no-frills
performance on medium and long waves.
Bush DAC90A in
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.