Technics SL-1700 no arm return help

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paddypaws
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Technics SL-1700 no arm return help

Post by paddypaws » 14 Sep 2019 16:38

Hi I have a Techinics SL-1700 bought second hand. Its all working well except the arm return, the one thing I bought a SL-1700 for! unfortunately at the end of the record the arm lifts off the record but doesn't move back to the arm rest. It doesn't move at all not even a little bit, just lifts and the platter continues to spin. Then if you press the 'stop' button the arm will then move back to the rest but stays up and doesn't settle on the rest. The platter then stops. Pressing the cueing button sets the arm down. Obviously most of it is working it can't be much! Any thoughts and ideas welcome. I'm baffled.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 15 Sep 2019 08:47

The more I think about it the more I’m convinced this is an electronic fault, the arm is doing all the moves it should just not being triggered at the right time (at the end of the record). It detects the end of the record because the arm lifts then stops. I must have an electronic control board fault.

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Re: Technics SL-1700 no arm return help

Post by akimmet » 16 Sep 2019 16:13

These turntables have a mechanical return, there isn't an electronic control.
It is most likely something is getting stuck from old grease underneath.
Cleaning and re-applying proper grease almost always fixes things.
If that doesn't fix it, the next step would be to clean and adjust the end of record return switch underneath.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 16 Sep 2019 18:00

Thanks for the reply, akimmet . I have just realised it’s a sl-1700 mk2 sorry my mistake - so it has got a whole board dedicated to the arm logic control circuit. The arm it’s self works because I can return the arm by pressing ‘stop’. It just doesn’t return at the end of the record because the arm motor stops after lifting the arm.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 16 Sep 2019 19:05

I can't edit the title. But to make it clear its an sl-1700 mk2.

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Re: Technics SL-1700 no arm return help

Post by Japi Roelofs » 16 Sep 2019 20:53

Hi paddypaws,

if you look at the SL-1700 page in the Library, you'll find —next to the user- and servicemanuals— the 'Technical Bulletin' that I uploaded a while ago. It describes a couple of types of 'misbehaviour' that can occur on both the SL-1700MK2 and it's fully automatic brother the SL-1600MK2.

The tonearm's automatic function works with sensors (for tonearm position detection), switches, and a small motor that drives a couple of gears. In the bulletin it is described how mis-alignment of the switches can cause trouble. For example Symptom B: "Cueing (UP) and auto return do not operate but cut operation is normal". ('cut operation' means pushing the Stop button, and tonearm returns to rest).

While this does not sound exactly like your problem, it could have something to do with the alignment of those switches.

Having said that....

Just yesterday I was working on an SL-1600MK2, that showed some weird behaviour too: when pressing the cue button, the arm would raise, but instead of staying above the arm rest, it would travel towards the center of the platter, and stay there, while the motor kept running. I fiddled a bit with the switch position, but no dice. After examing the mechanism a bit further, I found out that the bigger one of the two plastic white gears had a problem. There's a metal pole sticking out underneath, which falls into a slot on a black plastic piece. This black plastic piece (or 'cam') operates the switches. The metal pole from the white gear had gotten loose, and even though it could still transport the arm, it wouldn't return the black plastic cam in the right position. As a result the switch would remain open and the sequence would be 'off' so the motor kept running.
Fortunately I have a donor unit that I could take the gear off and replace it.

So do check the technical bulletin, it might have the answer. There could of course be electronic problems as well, but that would seem less likely.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 16 Sep 2019 21:32

Thanks very much for your help Japi Roelofs, I’ll look at the suggestions you have made and read the tech bulletin.

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Re: Technics SL-1700 no arm return help

Post by Japi Roelofs » 17 Sep 2019 00:01

Looking at the technical bulletin again, I noticed in the pictures of the underside of the tonearm that the black plastic cam on the 1600 is actually white on the 1700. Go figure...

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Re: Technics SL-1700 no arm return help

Post by chgc » 17 Sep 2019 02:41

akimmet and Japi Roelofs have already covered key areas. I just want to add that, unless and until someone cleans and lubricates the mechanism, you are unlikely to solve the problem, in my opinion. This will entail checking and readjusting sensors and such, but you can’t really get a handle on what needs adjusting until the mechanism is freed up. Sticky grease, dirt, corrosion, loose belts, hardened rubber, all but guarantee impaired function, even on MK 2’s.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 17 Sep 2019 10:21

The grease seems fine, I will clean up the cams and worm gear and re lubricate everything and report back. Are there any good instructions or videos people know about disassembling the arm mechanism and re aligning everything?

However I still think I have an electronic logic problem because the arm performs fine when you hit 'stop'. It returns to the arm rest as it should. It just doesn't return at the end of the record, it just lifts and stops so it is detecting the lead out of the groove.
If it was hampered by mechanical problems or dry grease it wouldn't work under any circumstances.

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Re: Technics SL-1700 no arm return help

Post by chgc » 17 Sep 2019 16:38

I don’t know what’s wrong with your turntable, but I figured it’s probably wise to clean/lube before messing with the electronics.

This video features an SL1600 MK2, but it has some good information. I only watched it once a few months ago. I don’t know if everything in it is correct or a good idea (e.g. I think he installs the shipping screws at the end). But at least it’s fun viewing if you’re into that sort of thing.

https://www.youtube.com/watch?v=HmZ_Nfo-dRw

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 17 Sep 2019 20:45

Thanks for the help so far . I’ll clean the arm gears put new grease on them add a new belt, it’ll be good insurance policy for the future anyway. For the actual auto arm return fault the logic chip IC501 (TC4011) has my suspicions and I’ve ordered one as they are inexpensive. If after cleaning etc if the fault remains this is the next step.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 21 Sep 2019 14:08

I’ve done some work on the turntable and I’ve cleaned up the gears and worm gear and re greased with a light silicone grease. The arm is working smooth and fine when you press stop but auto return is still not working. Still exactly the same problem it lifts the arm at the end of the side but doesn’t return to the rest. The motor power is cutting off too early because if I power the arm motor with a bench power supply it all works fine lifts and returns. I decided to replace ic 501 the cmos chip on the arm board but that made no difference. There is a variable resistor on the arm drive board marked ‘auto return time’. The service manual skips over it. Anyone know what that does or have anymore ideas for me?

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Re: Technics SL-1700 no arm return help

Post by Tom_Technics » 22 Sep 2019 00:29

Classic symptom of failed IC's or electrolytic capacitors in the arm control circuitry. Has your 1700mk2 ever been serviced? If not, a thorough top to bottom electronic and mechanical overhaul is seriously overdue for this machine.

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Re: Technics SL-1700 no arm return help

Post by paddypaws » 22 Sep 2019 06:51

Hi Tom_Technics, no as far as I can tell i'm the first person to take it apart judging by all the dirt that is inside. Are there any places to get a full service done on this deck, I might just do that. There seems to be loads of places that will do 1200's but obviously a 1700 is more complex. Its cosmetically excellent so would be worth doing.

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