Technics SL-1700 mk2 Target light

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paddypaws
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Technics SL-1700 mk2 Target light

Post by paddypaws » 12 Oct 2019 11:14

The target light bulb on my sl-1700 is out. I’m thinking if replacing it with one of the kits on eBay that have a surface mount led on a piece of board that shines sideways through the slot. I’ll keep it warm white for original looks.

My question is - is the sl-1700 the same bulb and light and voltage as the sl-1200? (The kit only mentions sl-1200 compatible).
Incidentally anyone know why there’s a resistor on the switch of the target light?

chiz
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Re: Technics SL-1700 mk2 Target light

Post by chiz » 12 Oct 2019 11:57

The 1700MK2 does share some parts with the 1200MK2 and it's possible the target light is the same.
You can find the service manuals here and compare part numbers and circuit diagrams:
https://www.vinylengine.com/library/technics.shtml
Last edited by chiz on 12 Oct 2019 12:05, edited 1 time in total.

Japi Roelofs
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Re: Technics SL-1700 mk2 Target light

Post by Japi Roelofs » 12 Oct 2019 12:04

I tried this once: I put a target light bulb for an SL-1200MK2 in an SL-1600MK2, but the light was very dim. Not sure if I had a bad bulb, or if the lights are actually different.

paddypaws
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Re: Technics SL-1700 mk2 Target light

Post by paddypaws » 12 Oct 2019 12:34

Thanks - looking at the two service manuals the part number for the ‘lamp’ is the same on both decks. Unless the resistor is different. I’ll see if I can find it in the manuals.

paddypaws
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Re: Technics SL-1700 mk2 Target light

Post by paddypaws » 12 Oct 2019 18:31

The circuit diagrams indicate that the sl-1200 feeds the target light with 20 volts but the sl-1700 feeds the target light with 12 volts. This is probably why you noticed the lamp was dim from a sl-1200 japi Roelofs. However the part numbers for the lamp on the parts list in the manuals are the same, I don’t understand!
Also the resistor on the switch is in parallel to the switch,therefore it’s only in circuit when the switch is off, what’s that about!?

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Re: Technics SL-1700 mk2 Target light

Post by paddypaws » 13 Oct 2019 09:48

Commenting on my own question, I think the resistor across the switch keeps the bulb conducting a small amount of current to help limit the inrush when switching on and to help prevent the bulb blowing and the driver circuit stress. I'm guessing here its not needed for an LED conversion.

sylvain999
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Re: Technics SL-1700 mk2 Target light

Post by sylvain999 » 23 Oct 2019 17:05

paddypaws wrote:
13 Oct 2019 09:48
Commenting on my own question, I think the resistor across the switch keeps the bulb conducting a small amount of current to help limit the inrush when switching on and to help prevent the bulb blowing and the driver circuit stress. I'm guessing here its not needed for an LED conversion.
Never made a led conversion on a 1700 mk2, but on a 1200, i use the built in 1.5k resistor, cut it off the switch, and put it in series on the positive side of the led, works like a charm. I guess a 1k resistor would be fine for 12 volts. I also use the plastic base of the old neon as a spacer to get the led at the right level. I cut the neon off and drill the inside empty to insert the led. I pry the head of the led 90 degrees cause leds are not brighning much from the side, you want the round head targeting directly to the arm. I use the smaller kind of round led, makes it much easier to fit in. Then i insulate both legs with shrink so they don' t short together, once the leads soldered. I keep the old neon wiring i just make sure which lead is positive, so i don' t have to re thread a wire in which is a pain.

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Re: Technics SL-1700 mk2 Target light

Post by paddypaws » 23 Oct 2019 17:27

sylvain999 wrote:
23 Oct 2019 17:05
paddypaws wrote:
13 Oct 2019 09:48
Commenting on my own question, I think the resistor across the switch keeps the bulb conducting a small amount of current to help limit the inrush when switching on and to help prevent the bulb blowing and the driver circuit stress. I'm guessing here its not needed for an LED conversion.
Never made a led conversion on a 1700 mk2, but on a 1200, i use the built in 1.5k resistor, cut it off the switch, and put it in series on the positive side of the led, works like a charm. I guess a 1k resistor would be fine for 12 volts. I also use the plastic base of the old neon as a spacer to get the led at the right level. I cut the neon off and drill the inside empty to insert the led. I pry the head of the led 90 degrees cause leds are not brighning much from the side, you want the round head targeting directly to the arm. I use the smaller kind of round led, makes it much easier to fit in. Then i insulate both legs with shrink so they don' t short together, once the leads soldered. I keep the old neon wiring i just make sure which lead is positive, so i don' t have to re thread a wire in which is a pain.
Thanks for this, that's pretty much what I've done, except I found a surface mount LED that is attached to a tiny circuit board on ebay that fits in the target light and just right for the job as its mounted in the right direction for the slot. I've discovered that the two pins that supply the light on a 1700 are at 12v and come off the logic / control board where as on the 1200 the target light is 20v and comes from the motor driver board. However on the 1700 you can use the same 20v points on the motor driver board, you just need to add a connector or solder to direct the board. I added a small molex connector.

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Re: Technics SL-1700 mk2 Target light

Post by Hannes_Hannes » 23 Oct 2019 21:11

I have just replaced my SL-1700 mk2 target light bulb with LED. I too thought that it is powered by 20-21 volts source but noticed it to be 12 volts during replacement work. However it turned out to be successful. I bought a 1.2 kohm resistor and a 2.8-3.8 volts 25mA white 8000 mcad LED and soldered these in series, not parallel. It is quite bright but could be even brighter at 21 volts power source.

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