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Q303 - Record size detection working on and off

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Q303 - Record size detection working on and off

Postby tehinternet » 09 Aug 2018 13:03

Hello,
So my TT has the cutout in the mat that allows for two "fingers" to detect if there is no record, a 7-inch record, or a 12-inch record present. My issue is that when I first turn on the TT after letting it sit overnight, when I hit the Start button it automatically moves the tonearm to what I suspect would be the starting point for a 7-inch record. Then I raise the arm, move it to the 12-inch starting point, and all subsequent records after that point while it's powered on work fine.

Looking at the little fingers, the one closer to the center for 7-inch detection seems to be good. I can manually press it in and it pops back out on its own. The 12-inch finger farther out though seems to be stuck down all the time.

If I take the platter off, I can move the lever under these fingers and then the 12-inch finger will pop up. But, if I let go of the lever everything moves back to how it was with the 12-inch detection stuck down.

This is weird, because I would think if the 12-inch is always down and a record places on the platter then lowers the 7-inch that all would be well. This is also very weird that it only happens the first record I play after turning it on.

Now if I turn it off quick and turn it back on, it will not reproduce. It needs to sit powered off for a bit before it does it again.

What am I missing here?


EDIT: And there's some pics of what the top side of these 'fingers' look like at the bottom of this thread: viewtopic.php?f=16&t=101140&p=910269&hilit=detection#p910269
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Re: Q303 - Record size detection working on and off

Postby tehinternet » 14 Aug 2018 14:24

A little update on this.

The issue seems to only happen when auto-start is used the first time it's powered on. I can play 20 records after this and they all go to the proper start position. But if I turn it off and back on immediately, the first auto-start will try to go to the 7" start position again. Then subsequent auto-starts work fine. If I power it on, but wait for about an hour to let it "warm up" that makes no change, the first auto-start will always goto the 7" position.

I took the service manual and tore it apart. Gears seems to move freely, appear well lubed. The tone arm moves freely and doesn't stutter or bounce around when moving automatically. I was able to reproduce manually triggering the no record/7" record/12" record states accurately each time. Mechanically it seems to detect the record correctly by moving a detection lever to specific positions for the 3 different record states.

The only things I can thing of at this time is there is something electrical happening after the first power on which overrides the mechanical detection of the size of record. Or for some reason on the first power on the mechanical detection gets thrown off and the indicator detects only a 7" record for some reason.

Anyone have any ideas on this one?
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Re: Q303 - Record size detection working on and off

Postby tehinternet » 19 Aug 2018 03:03

I ended up solving this and am posting in the chance it helps someone else. It ended up being a problem to the grease mostly likely where the index plate slides. It's the little plate that the fingers on the platter hit when it does the size detection.

The first time I took it apart I didn't think it was a grease problem because everything was moving freely and the grease seemed 'okay'. My problem was I took it apart after playing a couple records in the table. I should have taken it apart after it sat for a day or two and then see if anything was stuck.

My theory is after the table sits for a day or two the grease would get tacky and after power on and hitting 'Start' it would have a tough time breaking free and messing up the detection. But, after that, then it would work well.

So, I took it apart a second time. I didn't re-grease everything, but I removed the grease, cleaned, and applied white lithium grease on everything I could easily access after the tone arm unit was removed. So far it's 4 days consecutively running well and starts perfectly each time.
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Re: Q303 - Record size detection working on and off

Postby AsOriginallyRecorded » 19 Aug 2018 03:17

Thank you for the posting and investigation of the situation. This is indeed something that may apply to a variety of turntables. I have several linear trackers, and know from experience similar to yours that the correct type and amount of lubricant can make significant differences on playback. The real beauty of this site is the sharing of information among members. You are now part of that....thank you! Cheers! =D>
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Re: Q303 - Record size detection working on and off

Postby sylvain999 » 19 Aug 2018 20:49

tehinternet wrote:I ended up solving this and am posting in the chance it helps someone else. It ended up being a problem to the grease mostly likely where the index plate slides. It's the little plate that the fingers on the platter hit when it does the size detection.

The first time I took it apart I didn't think it was a grease problem because everything was moving freely and the grease seemed 'okay'. My problem was I took it apart after playing a couple records in the table. I should have taken it apart after it sat for a day or two and then see if anything was stuck.

My theory is after the table sits for a day or two the grease would get tacky and after power on and hitting 'Start' it would have a tough time breaking free and messing up the detection. But, after that, then it would work well.

So, I took it apart a second time. I didn't re-grease everything, but I removed the grease, cleaned, and applied white lithium grease on everything I could easily access after the tone arm unit was removed. So far it's 4 days consecutively running well and starts perfectly each time.

Personally i am staying away of lithium grease. I am servicing many Technics and i begin to see some serviced 2-3years before with Lithium grease that begins to stick too much. Originaly the brown grease acted more like a damper for quieting the gears operation and have them feel smooth by removing the gap between gears. I never grease them back, it feels less smooth and more clunky/noisy but those gears never spins fast anough to wear and they never get back for servicing again. I will grease only if operation gets very noisy like metal on metal parts, or if there is a lot of pressure from a metal part on plastic/nylon gears.
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