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Logic Dm101 electronic speed controller repair

keithsnaim

keithsnaim

Gone Fishing
So after 40 years of almost daily use my turntable has finally died. All I've had to do is replace the belt and oil periodically. Guess I've been lucky knowing the problems that people have had over the years with the speed controller failing.
I turned the deck on yesterday to find both the 33 and 45 rpm leds light up simultaneously, then fade and go out. I don't like to move the deck due to the sprung sub chassis being so flimsy and the springs are now unobtainable, but I decided to have a bash at repairing the controller.
So last night I removed the outer and inner platter and inserted the original spindle hole plug to stop oil spillage. Then I locked the sub chassis down with the original transit bolts.
I then stood the deck on its side to reveal the controller cover. Removed this, then the 3 screws holding the pcb to the underside of the plinth.
Dropped the pcb down and disconnected the wires to the mains and pulley. I now have the controller pcb on the bench. Looks like the 15k resistors, 22uf axial caps and a few more resistors need replacing. One TIP49 looks like it's been cooked too. I've ordered parts this morning from cricklewood with the exception of the TIP49 ( obsolete) and got a substitute.
I will post up some photos later.
 
Hope you get it sorted, it’s a really nice turntable. I swithered between it and the original Systemdek back in the day. Went with the Systemdek but always admired my friends Logic.
 
Nice one. My friend and I both had the original Mission arm and the same cartridge on our decks, can’t remember what it was and they both sounded great.
 
My photo bucket account will not allow me to share photos unless I pay a fee, what do you guy's use?.
 
Certainly looks salvageable.

If not, you could always go back to the old 2 x capacitor network on a terminal strip with standard power switch. At least this would keep the records spinning whilst you come up with an alternative.

Same as Linn prior to the pre-Valhalla PCB, only minus the nice Molex strip.

P1010630.jpg
 
New parts fitted and the deck is up and running. I had to change the suspension rubber mounting grommets because they had perished away. Found a set of grommets at toolstation for £2.27. Just needed to shape one side of them with a craft knife to make them fit.
Haven't tried it in the system yet to see if the speed needs adjustment.
 
The deck is set up in the system now. Managed to get the bounce of the sub chassis just right, it's probably the best it's ever been. On initial listening it appears to be running a little bit on the slow side. A new belt is required before I mess about with the speed trim pots. Then I will probably need a strobe disk to get it spot on.
 
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