Although I had got to know Mike while he was starting MRM, I didn't have any input into the Source until it was bought over, when I re-did the electrics, getting rid of the strange LED wiring and speed switching (which sometimes causes spurious cogging of the platter when it was supposed to be switched off), and giving my thoughts on the psu.
The original big box MRM supply used two 90VA EI transformers wired in parallel to give 24v ac which was rectified and smoothed with a capacitor which had all markings removed - Mike liked to be secretive. It was actually a 3300 microFarad/100v Sprague electrolytic. I know, because I had a large batch of these and sold them to Mike.
The Papst motor was not very reliable or sturdy, both electrically and mechanically, and feeding almost 36v into it was asking a lot. If it was me I'd change it or use a lower voltage. The same motor was used in a Sota Sapphire and also in Oracle and Goldmund models.
In brief, the early ac motor using the on board rectifier had a recommended voltage of 16 to 24 v ac.
The dc version had a recommended voltage of between 21.5 and 32.5 v dc.
If buying an alternative psu you should not excede these voltages, particularly if the psu is regulated.
In brief, the early ac motor using the on board rectifier had a recommended voltage of 16 to 24 v ac.
The dc version had a recommended voltage of between 21.5 and 32.5 v dc.
If buying an alternative psu you should not excede these voltages, particularly if the psu is regulated.
The later S.O. deck had a more elegant looking psu with two parallel 50VA toroidals. They were, (at least in my own one which I made myself) 18v each (9+9), with a slimmer lower voltage, higher capacitance capacitor.
The Source originally used some parts which Mike bought from STD, or had made by them, namely springs, switches, fastners, mats, suspension parts, arm boards, lid hinges, and the original perspex cover.
The Sub-chassis was steel, as was the top plate.
The platter and sub platter were phosphor bronze. On some custom decks these were gold plated.
The original mat was rubber with a brown nextel-covered cloth outer. This was soon changed to a black felt mat.
The bearing was a ground spindle with a centre drilled end which located on a 8mm (5/16")steel ball running on a hardened steel plate held captive in a brass turning which was threaded and fastened to the sub-chassis plate with a large nut and washer.
The conical springs had hard rubber mounts top and bottom.
The motor had a soft rubber mount top and bottom.
The plinth was mahogany or oak. The mahogany was either painted black or clear laquered, and the oak was stained light or dark. There were some custom plinths in rosewood.
The bottom cover was plywood.
The feet were originally rubber, then brass cones, or Topolinos, as Mike called them.
The arm board was MDF.
The power connector was originally a DIN speaker plug, latter changed to an XLR.
The sub-chassis, top plate, and motor casing were earthed together and wired to an earth post on the rear of the deck.
The belt was the same size as the Thorens 125, 150, 160: Thorens Part Number 6800574.
Latterly, the SO deck simplified the manufacturing, using a large aluminium alloy sub-platter and a phosphor bronze outer ring. The sub-chassis was MDF.
I had a budget design on the drawing board which never made prototype... but I used the principle, if not the budget parts, in a deck I made for myself:
I had a budget design on the drawing board which never made prototype... but I used the principle, if not the budget parts, in a deck I made for myself:
