Technics SL-1800 MK1 Ground Cable Help Needed

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RetroTech
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Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 24 Sep 2018 02:20

Hey guys, I recently purchased a used Technics SL-1800 and it is producing a terrible hum, but there is no ground cable present on the unit that I can find. Looking through the user manual, I see there is supposed to be one, but there is none. Looking through images on Google, I've seen where it appears that the factory ground cable exits with the RCA cables, but where would I solder a new one too? Anyone have pictures? I've also tried to find a service manual online with no luck. Thanks in advance for any Help you could send my way.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by abril » 24 Sep 2018 08:33

https://www.vinylengine.com/library/tec ... 1800.shtml
Service manual for Mk2 here
A quick search and found this
https://www.audioasylum.com/messages/vi ... ii-tonearm
Note the spade connectors on the underside of the arm?

RetroTech
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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 24 Sep 2018 11:10

abril wrote:https://www.vinylengine.com/library/tec ... 1800.shtml
Service manual for Mk2 here
A quick search and found this
https://www.audioasylum.com/messages/vi ... ii-tonearm
Note the spade connectors on the underside of the arm?
Thanks for all the advice. So the Mk2 and the Mk1 are the same in regards to the ground wire? Mine is a Mk1.

abril
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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by abril » 24 Sep 2018 11:16

I would expect them to be very similar for basic wiring.
Never had one though so don't know for certain.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 24 Sep 2018 11:47

abril wrote:I would expect them to be very similar for basic wiring.
Never had one though so don't know for certain.
If I were a betting man, I'd say the same. This is my first decent TT though, so I'm a complete noob to this game. Been watching a ton of videos on setup and routine maintenance. Can't wait to get this hum out.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by abril » 24 Sep 2018 12:58

Is it a hum or a buzz,a hum suggests a ground loop (too many ground points).
A buzz suggests no ground.
What cartridge is fitted?

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by akimmet » 24 Sep 2018 15:04

The closest models to the SL-1800 MK1 that have a service manual here on vinylengine are the SL-1600 and SL-1700 MK1. The MK2 models are different enough to not be very useful for Mk1 models.

I have had my SL-1800 Mk1 apart in the past. If I remember correctly, the ground wire and RCA cables go to a small PCB with a connector. This PCB should be the place where the original external ground wire was attached.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 24 Sep 2018 16:51

abril wrote:Is it a hum or a buzz,a hum suggests a ground loop (too many ground points).
A buzz suggests no ground.
What cartridge is fitted?
I would call it a hum more than a buzz, but I don't see any ground cables at all. I'll update further when I get a chance to tear into it and find out for sure.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 24 Sep 2018 16:51

akimmet wrote:The closest models to the SL-1800 MK1 that have a service manual here on vinylengine are the SL-1600 and SL-1700 MK1. The MK2 models are different enough to not be very useful for Mk1 models.

I have had my SL-1800 Mk1 apart in the past. If I remember correctly, the ground wire and RCA cables go to a small PCB with a connector. This PCB should be the place where the original external ground wire was attached.
Thank you for the Help, I really appreciate it. I'll update here when I get a chance to tear into it with my findings.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by abril » 24 Sep 2018 21:34

If it is hum it suggests a ground loop rather than no ground,beware of doing work that is not needed if you have a cartridge with a small,thin ground strap connected to one of the pins as many cartridges did have at one time.
You can see the straps here
38397

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by Dirty_Al » 24 Sep 2018 23:56

I had a similar Technics turntable with the same issue: Low level buzzing and no ground wire. There was, however, a jack on the back panel (next to the red and white audio RCAs) for a ground wire.

I found "Turntable Needles, Inc.' had the very part I needed! Try www.turntableneedles.com
using part number SFEL028-01E.

It would have been less expensive to pull the bottom cover off and hardwire a ground wire onto the machine but I wanted to keep it as close to stock as I could.

I was a pretty happy camper. Your mileage may, of course, vary!

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 25 Sep 2018 13:22

abril wrote:If it is hum it suggests a ground loop rather than no ground,beware of doing work that is not needed if you have a cartridge with a small,thin ground strap connected to one of the pins as many cartridges did have at one time.
You can see the straps here
38397
I will definitely check into that as well. Thanks.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by RetroTech » 25 Sep 2018 13:24

Dirty_Al wrote:I had a similar Technics turntable with the same issue: Low level buzzing and no ground wire. There was, however, a jack on the back panel (next to the red and white audio RCAs) for a ground wire.

I found "Turntable Needles, Inc.' had the very part I needed! Try http://www.turntableneedles.com
using part number SFEL028-01E.

It would have been less expensive to pull the bottom cover off and hardwire a ground wire onto the machine but I wanted to keep it as close to stock as I could.

I was a pretty happy camper. Your mileage may, of course, vary!
Yep, that's the first thing I looked for, but also there are zero output jacks on the rear of the SL-1800. The wires come through the back on a rubber grommet from where they are hard wired inside.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by akimmet » 25 Sep 2018 23:07

Correct, the ground wire and rca cables are hardwired on the SL-1800.

A common DJ modification was to ground through the rca cables. One would open the turntable, attach the grounding point to the shield of one of the rca cables. The original grounding wire was then removed.

This modification tended to create ground loop issues when used with most home stereos.

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Re: Technics SL-1800 MK1 Ground Cable Help Needed

Post by musicmn » 26 Sep 2018 01:19

Hi Retro Tech, I just finished up servicing and SL 1800 Before I closed it up I took some pictures of the motor drive board and just by chance the circuit board where the rca cables are attached. The red arrow in the picture is where the ground wire is soldered on. I hope this helps.
Attachments
technics SL 1800 mk1 003 (Copy).JPG

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