The right motor, a Garrard 401, installed on the EMI 917 'Disk Defect Defector'

I have received this extremely detailed description of how this machine worked from mr Arthur Work, and I pass it to the readers of my site with many thanks to mr Work for his words.

" I don't know if you still have your EMI Disk Detect Detector but I was pleased to see the image.You said you did not know how it worked. I hope this helps?
I was a EMI apprentice at EMI Hayes Middlesex in 1968.

I worked the the Recording Equipment Production Dependent (REPD) assembling the Disc Defect Detectors. or 'D3' (D cubed) as they were locally known.

I remember rooms of these machines being used for sample quality control of the record pressings from the pressing room in the factory.

The Disc Defect Detector played the records backWhards from the centre outwards. The principle being that a 'Pop' or a 'Scratch' has the same sharp rise and fall whether played backWhard or forwards. Whereas music could have a loud sudden crescendo that would naturally fade in volume.

The machines were fitted with Garrard 301 or later Garrard 401 turntables. The Squirrel cage motor in the turntable had being assembled with the driven squirrel cage fitted  fitted in the motor housing so that it was upside down to the normal assembly. This caused the motor to run backWhards and hence the turntable ran backWhards. Reassembling the motor correctly would restore normal operation.

The straight pickup arm were (if I remember correctly) supplied by Ortofon. The straight arm as opposed to to the normal 'S' shape arm was to allow the pickup to track the record whilst running backWhards. I believe the Stanton pickup cartridges has special needles designed with the slope to cater for the backWhards running of record.

Attached to the pickup arm were a electro magnet plunger that would be operated when a defect was detected. This plunger struck a conductive paper slip and an electrical current produced a mark on the paper. There was also a right angle plate fitted that when it passed a optical sensor that cut the power to the turntable otherwise the pickup would have drifted off of record as it would have now reached what was the original 'lead in track'.

The operators would collect the slips and records from each machine and any 'marked' ones together with their record would be passed to a listening room for further tests.

In the listening room the quality control staff would place the record on a normal record player that also had a position for the marked defect strip. They had a special gauge that fitted over the slip and from that with another guide they could align the pickup arm at the approximate position of the defect on the record so that they could check it. I seem to remember they all worn AKG headphones.

I can't remember much about the electronics of the unit other then it used plug in cards into a card housing which I think was on the right hand side?

The pressroom support engineers used to calibrate these machines every week to ensure consistent quality.
Hope this helps."