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Technics linear trackers like SL-7

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 18 Dec 2021 at 7:48pm
I am about to reset the arm servo on an SL-DL1 which has the same arm and servo circuit as the SL-7 so decided to revisit my previous work on this. First of all I think the Technics 1mm pitch test record was/is a widely spaced groove, 7 or 8 times the average groove spacing or pitch on an LP. I wanted something nearer to the Technics 1mm and for it to be a fixed pitch for ease of measurement with a digital multimeter.

On an LP you have 20 minutes in 80 - 90mm width, go fo the maximum 90mm which happens in 20 x 33 1/3 = 667 revolutions, giving pitch of 0.135mm per revolution. Variable pitch lathes have been in use since the 1950's so the goove is further apart in the loud bits of music and closer in the quiet bits e.g. gaps between tracks. It is that dead space or silent groove that appeals because the groove is not modulated so not moving side to side (in and out), which would make it hard to measure the SL-7 arm servo voltage.

The Hifi News test LP no.2 has 20 seconds of silent groove that is well spaced. The track is 3mm across so the pitch is 0.3mm (= 3 / (20/60 x 33 1/3). Based on Technics' 0.6V for 1mm pitch I aimed for 180mV with my test track. The result sounded even better than before.

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 22 Dec 2021 at 10:07pm
The SL-DL1 was instructional as it showed how one mistake (not by me or Ifor!) had messed everything up and why you should always check the service manual.

The SL-DL1 was sticking, playing one revolution of the groove again and again. From reading up on the subject I expected to find the tonearm carriage wasn't sliding smoothly along the guide rail or the motor servo settings were wrong. The rail was a bit rough so I cleaned it with IPA then used fine wet and dry paper, same for the cylindrical bearing in the carriage that runs along the rail. I refitted it and adjusted the offset sensor position and the servo presets. Record still sticking so I took the guide rail, tonearm, and disc sensor PCB out. I noticed the string was slack but it wasn't the tensioning springs, in fact the string wasn't running on one of the pulleys but on its axle. I took the arm drive wheel off to get at the pulley and check the string, finding the circlip didn't have a washer underneath... When reassembled I could still hear a very quiet rubbing noise so I tried the only thing left and found the string was laid back to front on the drive wheel. It all works again now but this shows how careless work at some point in the 40 years had sabotaged the well engineered product that left the factory.

I fitted my LP Gear VS cartridge and am enjoying some LP's.



Edited by Fatmangolf - 22 Dec 2021 at 10:12pm
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 22 Dec 2021 at 10:34pm
With my writing about the SL-DL1 I thought it was time to rename the topic!

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CageyH Quote  Post ReplyReply Direct Link To This Post Posted: 23 Dec 2021 at 7:11am
Interesting stuff. Arm troubles are what put me off a linear tracker.
Kevin
European loan coordinator, based near Toulouse, France.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 26 Dec 2021 at 9:20am
Yes they need to set up right. Having worked on three I have a high opinion of the Technics linear trackers now.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 27 Dec 2021 at 10:09am
I also cleaned out the cueing mechanism and replaced the silicone oil that slows the arm drop and lift speed. I picked some 100,000 cSt fluid from a local RC model shop. At some point I will get a higher viscosity like 300,000 cSt but it is definitely better for now.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 16 Jan 2022 at 12:45pm
The 300,000 cSt (yes that would be 3 kSt but it is a flow speed measurement that reminded me of the Stint Meter used on golf greens) finally arrived a few days ago. The vendor was apologetic as the courier had sent it somewhere else and agreed to post it to me the second time...

Anyway it has done the job as the drop speed is now normal. I think this is the right viscosity of silicone oil if you need to refill a cueing cylinder but you'll need a few millilitres so the 60ml bottle will probably outlast me.

Whilst I had the tonearm assembly off the rail I drilled out the outer hole for the T4P locking screw. This means you can push the cartridge in and slide the screw across into the threaded hole on the far side. It was one of the few 'value improvements' in the SL-DL5 that I liked along with the screw having a plastic thumbwheel instead of a recessed hex or posidrive that means trying to get a screwdriver turning in the tight space between the lid and mechanism dust cover. Even then T4P is a lot easier than fine tuning a normal cartridge to achieve one of the alignments.

Also  I picked up a second? hand Oyaide BR12 to try on my SL-DL1. It is 2mm thicker so the SRA would be about 1 degree shallower at the start of an LP then reducing as the BR12 is concave or dished. You need a clamp for this but there is limited space due to the low profile lid height and the edge of the dustcover overlaps the record label so a smaller than normal weight or clamp is needed. I dismantled the (spare) Michell clamp that came with my GyroDec and fitted a disk of 5mm acrylic. I used a hole saw to give me a 90mm diameter disk, countersunk it for the clamp to engage on the short spindle and superglued an M8 washer on top to centre the mechanism. It does the job on the BR12 mat and the stock mat, but I have yet to listen to records on it. If I like it I will probably but small holes in BR12 so the disk-size LED's can shrine through to the sensors in the lid. I will find a neat way to cut the holes or slots, assuming first that I like the sound compared the original mat.



Edited by Fatmangolf - 16 Jan 2022 at 12:53pm
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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