If you have one of the above models then it is most likely you will be experiencing intermittent or distorted output on one or both channels which can often be remedied temporarily by moving the input selector. It appears that the original lubricant dries out over time and loses its 'self healing' properties and eventually leaves the contact area exposed thus allowing sulphation to take place (the same reason that the family silver goes dark!). This then becomes a semi-conducting surface and leads to the intermittent operation and has nothing to do with wear of the contacts (a popular but false myth perpetuated on various Audio forums). This refurbishment will restore the correct operation of this switch and will also include gold electroplating of the original silver switch contact surfaces to eliminate long term reoccurrence of the tarnishing. These switches are now long obsolete and hence this repair is your only option if you wish to continue enjoying your amplifier and have no wish to invest a 4 figure sum in it's new equivalent!
As part of the repair the amplifier is also serviced and any other minor defects are also remedied and each example spends roughly half a day on the workbench in total. The amplifier is then put through a full performance test before being declared fit for a new lease of life and tested for several hours into speaker before being declared fit for return. In particular these models are quite a poor design in that the signal path travels via several switches and relays all of which have been found to suffer varying degrees of deterioration in many examples and further contribute to an intermittent output and these components are all attended to as part of this overhaul. These latter issues are usually masked by the severity of the problems caused by the motorised selector though and virtually all users are unaware of these until the amplifier is on the workbench.
One or two customers ask as to the estimated longevity of this repair. The first gold plated switch was put into a Delta 290 back in February 2014 and is still running perfectly in the workshop in daily use and well over 100 examples have now been fitted to customers amplifiers (Mar 17). This is a very popular repair and rarely a week goes by without at least one example in the workshop for refurbishment.
The cost of return carriage to a UK mainland address is included in the above price.
Repairs include a 3 month guarantee.
Switch wafer example before.
Switch wafer example after refurbishment and gold plating