Technics SL-1710MK2. Pitch display. - UK Vintage Radio Repair and Restoration Discussion Forum

samjmann · 26th Jun 2019, 10:08 pm

A friend asked me to look at one of these turntables that had been an e-bay purchase. A few problems came to light: Continental type twin mains lead - only one covering on each conductor; arm lift not working and the pitch indicator stuck at the far right hand side.

The arm lift problem was nothing more than a perished belt. I replaced the mains lead with a UK spec cable and plug. The pitch control was a little more complex...

The circuit is made up of two C4011 nand gate IC's, a C4013 D type flip flop plus one other IC an AN6552, and the LED drive a SVIMS1901P. Apart from the supply virtually every voltage around the 4011/4013's were wrong. From what I could see in the manual this forms an oscillator running at 269.94Khz. The TT speed was perfect, and could be adjusted with the pitch control, it was just the LED display that was wrong. The actual fault was the IC425 C4013. After replacing this the display worked and with a tweak of the pitch gain pre-set, the indicator worked as it should. This all seems a very complex way of going on, but in typical Technics fashion, it worked very well.
After spending a lot of time looking the circuit I'm still not sure how it works,but at least it's fixed.

Anyone had any involvement with one of these turntables?

The full circuit is on the Vinyl Engine website if anyone wants a look.

Cheers, SJM.

26th Jun 2019, 10:08 pm	#1
samjmann Heptode Join Date: Feb 2014 Location: Nottingham, UK. Posts: 648	Technics SL-1710MK2. Pitch display. A friend asked me to look at one of these turntables that had been an e-bay purchase. A few problems came to light: Continental type twin mains lead - only one covering on each conductor; arm lift not working and the pitch indicator stuck at the far right hand side. The arm lift problem was nothing more than a perished belt. I replaced the mains lead with a UK spec cable and plug. The pitch control was a little more complex... The circuit is made up of two C4011 nand gate IC's, a C4013 D type flip flop plus one other IC an AN6552, and the LED drive a SVIMS1901P. Apart from the supply virtually every voltage around the 4011/4013's were wrong. From what I could see in the manual this forms an oscillator running at 269.94Khz. The TT speed was perfect, and could be adjusted with the pitch control, it was just the LED display that was wrong. The actual fault was the IC425 C4013. After replacing this the display worked and with a tweak of the pitch gain pre-set, the indicator worked as it should. This all seems a very complex way of going on, but in typical Technics fashion, it worked very well. After spending a lot of time looking the circuit I'm still not sure how it works,but at least it's fixed. Anyone had any involvement with one of these turntables? The full circuit is on the Vinyl Engine website if anyone wants a look. Cheers, SJM.