tip: click on the thumbnail image to view the full size photo.
November 26, 2004
Today the Prestige project went a little further. I took a look at the
electronic parts. The power supply board with the both motor drive amplifiers I
found in stock, also the generator board. But not a trace of a new interface
board. The most important, and most complicated, board of this turntable.
I found an old used and damaged one, important to get an impression of the
design, but unusable for this project. But there are empty print boards, so I
decided to built up a new interface board. Because it is more effective I
decided also to build up two boards parallel, one in reserve.
November 30, 2004
"Over the past few days the Prestige project was powered up mighty by important new discoveries of information and material. In the beginning, I set up the front panel using every kind of screw I could find. Step by step, closer and closer, to measure the correct dimension to make the tip bottoms able to work.
Image 74 shows the result from the backview.
Image 75 shows the front view.........and........
Image 76 in detail. A chaotic assembly but only made to establish the needed dimensions.
After all this, with an impression of the part I need in my head, I went into stock to search and I found the original spacers. Image 77 shows the result. But I found something more; the original pitch poti with assembly kit and knob. The most important part of all.
December 1, 2004
I found the one and only, last remaining, interface board. It seems intact and in good condition. But I don't know -- will it work? So I decided to continue building up the two new interface boards, but the first try will be with the original one.
Photos 78 and 79 show the pitch poti assembly.
Photos 80 and 81 show the new interface board assembled to the front panel.
December 2, 2004
"Now I think I have a proper perspective on what an "interface board" is to a Thorens Prestige. It receives input from the user, who pushes a switch and then the board routs the signal where it needs to go." -Steve
"The Interface Board is operating with TTL technology of the 80s. It is the heart of the Prestige, similar to the TD524 and 738." --Rolf
The heart is assembled. Let's take a look if it is willing to beat...
Today I was just trying to test the power supply unit. Therefore I tried to assemble it to the base plate. I thought it would be simple work. The power supply board has 6 screw holes so I thought 6 screws, 6 spacers and 6 screw holes on the base will do the job. Not on a Prestige. Because these parts are missing from the beginning, I had no real impression. The Prestige designers did their very best to create the most complicated print board holder I have ever seen in my life. It took 2 hours time to look in old drawings for parts with the same drilling positions,--an indicator for me--to assemble these parts together and look for the result. I was most happy to find all these parts in stock at last.
Here is the result:
Photo 82 shows all needed parts for assembling this little print board. Left side on the print you can see the motor drive output stages. Rightside is the main power section.
The generator board has a similar base construction. I looked in stock parallel for this parts but I couldn't find "groundplate 2", so it will be reproduced over the next days, no problem, I found it's drawing..........
Also the power connector board was taken away from the old upper face plate, cleaned and painted anew, then it was placed in the original position under the lower base plate.
December 3, 2004
Further explanation of the Prestige electronics:
The Prestige electronic components are divided into 3 sections on separate printed circuit boards plus one external transformer.
It creates the 4 DC voltages for the turntable. Two voltages ( +- 15 volt) are stabilized and used for the interface board. The other two ( +- 25V) are for the lift function and are not stabilized. The power supply unit also carries the two power output stages for the motor drive. This board is running free, always in function if the turntable is switched on.
2. The generator board.
The generator board is an oscillator synchronized by an external trigger pulse, switch-able to 3 frequencies, leading to the 3 rotation speeds of the platter. Generator output is directly fitted to the output stage on the power unit. Generator input (on/off, trigger pulse, speed select) are TTL (5 V high level) voltages created by the interface board.
3. The interface board.
The interface board is the center of all electronic equipment of the Prestige. Turning on the turntable, the interface board will be reset. That means, stop position, both lifts up, 33-1.3 pre selected. The board will create defined TTL voltages and send it via bus cable to the generator board (generator stop) and to the lift amplifiers, positioned right on the interface board.
Then the board is waiting for some information from the tip bottoms. If you push start, the board will create a TTL voltage sent via bus cable to the generator to start working with the selected speed. Also the quartz oscillator on the interface starts to work, sending his pulses out to the generator for synchronizing. The platter will start to rotate. In rotation, the platter will activate the tacho generator on its downside. These signals are lead back to the interface and will be compared with the quartz oscillator. In the PLL section (Phase locked loop) the generator will be fitted with exactly the pulses matching the right speed.
The pitch section adds an offset to this pulse, if selected. The platter will run constant 0...6% faster or slower than main speed.
Also part of the interface are two separate auto shut off functions. They are working similar to the TD 126 and will cause a reset of the interface board.
December 4, 2004
Today the generator board gets its new mounting base. I made it from 1mm steel after the original drawing from an old EMT chassis part. The surface was polished and secured by a foil over the years.
Above image #90: the new mounting base for the generator board.
96) The details of the interface board. In front you see the two lift amplifiers. They are not connected (3 empty green cable sockets) because no lift is assembled. Behind you see the pitch control section (the 4 pole cable) and the lift control, at last on the tables left side the speed select, quartz oscillator and PLL section.
December 7, 2004
Today was a great day for the Prestige project. First, I found a second version of the pitch knob, matching perfectly in color to the tip bottoms. The new knob is a full metal version without plastic inlet underside.
Photos 89 and 99 are showing the differences between the two styles of pitch knob.
tip: click on thumbnail image to see the full size photo.