Technics SL1200 turntable wants to be their own DJ

Life Technology
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Ok… I got a problem with this Technics SL1200… this video explains it all…

By the way the tonearm would not track at all at first, it would snap right into the middle HARD, and it was because the lateral bearing got deformed (it was made of some very soft metal). I dug that bearing out, and unfortunately that style of bearing wasn’t made anymore, so I reamed the hole in the tonearm assembly to fit a MR52ZZ bearing. That fixed the tonearm and now it tracks correctly.

But the self DJ problem, well I believe it’s related to some control IC in the board. When I first got the thing, it turned just fine, but a few minutes later I went to turn it on and it started doing this.

And I tried reflowing the solder on the board to rule out bad connections (since it worked once and it stopped working suddenly, I figure it was that), but that didn’t fix anything.

Problem is the IC’s on the board is some proprietary IC that isn’t made anymore, and they are selling for about 85 USD for just ONE of them. An entire board is about 200 USD. I have no idea which IC is bad, because I only have a multimeter, and no oscilloscope to measure waveform coming off the thing. I think I’ve isolated it to one IC, based on their voltage reading being REALLY off. However that IC cannot be found at all.

Owner is probably going to get the board at some point. I fixed the mechanical issue but electronic issues are a bit thorny.

Anyone have suggestions? Do you think there’s any way to modify the board for it to work with standard control IC?

Worst comes to worst, get a BLDC motor driver, an Arduino and program/wire it so that the buttons, dials, strobe, pitch shift, etc. all work.

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It’d be very weird/unlucky if when you got the thing it was working just fine, then it broke because of a completely new issue a few minutes after that, wouldn’t it? Isn’t it possible that it’s an intermittent issue?

Aren’t there more specialized forums for enthusiasts discussing these kinds of repair issues? Maybe you should search to look for previous reports of this problem and possible solutions?

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There’s a turntable forum out there, that appears to have lots of good info, but unfortunately does not accept new accounts at the moment.

Owner of the deck told me it has been water damaged, I think, or it was dropped. No idea of their history. If it was water damaged then that could explain the erratic and intermittent behavior.

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https://www.vinylengine.com/turntable_forum/viewtopic.php?t=16874
caps sound like a common problem for old boards that might lead to symptoms like this.

Might try hitting the table with some deoxit just for kicks to see if it helps .

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I don’t know. I’ve reflowed solder in various places to rule out disconnection problem, but I’ve also measured the spec for the power cap and they are all within spec, so I doubt that is the problem. Nothing on the board look out of place, nothing bulged, burnt, or had the magic smoke let out. Everything appears completely normal except the thing just won’t turn right.

That Vinyl Engine site was what I was talking about. I tried to create an account but they are not allowing that at this time. So I can’t go there to ask.

I’ve also followed the troubleshooting guide on the service manual, and measured various voltages. Main voltage at TP5 is correct.

However on one of the smaller IC (labeled IC302) the voltage on some of the pins are REALLY out of wack. Like one where it’s supposed to be 2 volt is reading like 9 or 10 volts.

I think that chip might be the problem, but unfortunately that chip also isn’t available anywhere.

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have you tried measuring the capacitance of the caps?

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I have, they were all within spec.

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Caps have all been checked, all within spec, no external damage, all voltage to and from the power section checks out. The only thing that doesn’t check out is the control IC but these IC are costing more than what these turntables are worth.

Unless there’s a copy of those control IC, basically the code for these is AN6680, AN6685, AN6682, and SVITC4011BP

I honestly do not know which chip is bad, I suspect all of them to some degree, and I do not have an oscilloscope to figure out which is bad and which is not.

These chips are extremely expensive. Basically AN6680 sells on ebay for 85 USD, and AN6685 same. They’re this expensive because there’s a limited supply of them. But China copies all sorts of chips and those motion controller are mostly the same, so does anyone know if there’s Chinese copies of these chips out there? Or what companies making them? I’m pretty sure Technics/Panasonic doesn’t make them and is likely contracted out to someone, because they are making SL1200 turntables as of 2020.

Seriously I just need the damn platter to spin at 33 RPM, I don’t care how. If I have to I’ll just remove the motor drive from the board and use a BLDC motor driver to turn it, and use an arduino to make it light up the strobe and other pitch shift functions. Because proprietary chip sucks.

Seriously some of these chips are costing as much as an Intel 10th gen i7’s, and they’re not even THAT complicated.

Maybe just use Raspberry pi to just emulate the damn thing.

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If this is from VD, which was flooded in a typhoon, “submersed for a long period of time” might be a more accurate description. The guys entire basement was a swimming pool.

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Yea, I saw a bunch of records without the sleeves at VD, and he said it was flooded and so the sleeves all dissolved.

The turntables did come from VD. I have two of them. One of them is perfectly functional, the tonearm was a little springy but I adjusted the tension on the points and it fixed the tracking issue and now it works perfectly fine, just the RCA cable was dead, replaced that and now it works.

The other one was a trainwreck. I turned it on at first and it spins correctly but later on it did that back and forth thing. The bearing on the tonearm was a mess, where it snaps to the middle with considerable force. I had to remove the bearing (they look like they were made out of chineseum, softer than butter), ream out the hole and pressed a MR52ZZ bearing into it. That fixed the mechanical issue of that tonearm and now it tracks correctly.

But I’m not seeing any evidence of water damage on the turntable at all, except that it was covered in grime (perhaps from the water??). The internal electronic looks pristine and so it had me baffled.

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Just an update: I started playing detective on the thing. It’s hard to know what’s wrong when everything looks pristine and untouched yet it’s broken…

So I started by removing a transistor. This caused the turntable to spin correctly but at a much higher speed (like a CD player almost). I went and got a replacement transistor in case I thought it might have been damaged. I also got a bunch of caps just in case some might have burned out even though none looks that way and are all working and in spec (according to my measurements). Caps are cheap anyways.

None of that solved the issue. Putting a new transistor back in just made it do the washing machine motion again. In desperation, I have a perfectly functional Technics SL1200, so I took the AN6680 chip off that, and put it on the broken turntable. Well what do you know, it now spins correctly and functions perfectly fine.

Except this chip is rarer than hen’s teeth and people seem to know so little about it that not even China will copy it, so I can’t find it for anything less than about 100 USD just for the chip.

That transistor I just replaced got VERY hot during an hour of operation though, and the guy from VD runs them like 12 hours a day for YEARS. So I found a heat sink from a broken computer, cut it to size, and attached it to the transistor. Better safe than sorry.

Last thing I want is the AN6680 failing again.

Can’t believe there’s no Chinese copy of this thing. I heard there’s Technics SL1200 copy… I have to wonder if they have the same AN6680 chip in it, or even if not if they basically do the same thing.

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So update, the AN6680 is the culprit. Because after replacing the transistor and a few caps just in case, the turntable was still doing the washing machine thing.

So I took the an6680 from another turntable that does work correctly, and soldered it to the broken one, and what do you know, thing is fixed!

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Didn’t you already say that in your previous post yesterday?

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Sorry I forgot about it.

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Seems like you’ve fixed it anyway, just wasn’t sure why I was reading the same thing again…

Looks like you got a lot of useful technical advice on the Arduino forum. Maybe it’ll help.

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No, not really. I need an alternative for the an6680 and there isn’t one and the Chinese won’t copy them. I heard the 1200 mark 7 is junk, made in Malaysia and likely use a different drive system.

Everything points to getting another an6680 chip. Chip costs about 100 USD. I took it out of another good turntable so I still have one nonfunctioning one.

Going to ask the owner of the deck when he goes to Japan and see if he can perhaps get some technics main board. Even if it’s for a different model like 1300, 1600, 1700, they all use an6680 chip so I can rip it off them.

Stuff is repairable but not integrated circuits. There are no smd so I don’t have to bother Marco about using a rework station.

Modern turntables, especially all those Bluetooth stuff, can’t be fixed at all. Which is what makes these older decks more valuable.

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So do that then? I see they’re around 100 USD, but aren’t you just repairing it for someone else?

I was referring to your long, detailed conversations about doing something with an Arduino on here and other forums. Not much point discussing all that then is there, if the solution you’re going for is just buying the chip? It does seem like the best option…

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It’s more for future use, because those chips are just going to be one rarer and rarer. I also am trying to help the owner save money. An Arduino uno r3 can be had for like 150nt and they can do a lot if you know how to program them.

Might as well have the discussion before those chips start costing more than 1000 usd.

But if it’s the an6675 chip then it’s more screwed because that chip costs more, and the motor will not spin at all without it.

Goal is have replacement drives that can be customized off the shelf that can tie into existing motors in the turntable.

There’s a lot of 1200 with no guts. Mechanically I can easily fix it but electrically they need to spin.

Maybe one of those diy Arduino turntable kits out there…

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Yeah, but how many hours of your time have you spent now trying to help someone else save less than 100 USD? (I hope you’re being reimbursed for that.)

If the chip is the way to go, may as well just do it. It’s only 100 USD, and if it’s someone else’s money anyway…

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Just an update. Ended up buying a replacement chip for damn near 100 USD. Turntable works fine once a new chip was replaced (I took it from a working SL1200).

I found a shop near the tax office at Ximen that had drawers full of chips with the AN prefix on it, but sadly no 6680, 6675, or 6682. I really wish that those chip number can be cross referenced and a functional replacement that’s cheaper be found, as motion controllers tend to be somewhat similar. Those AN prefix chips were anywhere from 50 to 300nt each, depending on which one. Guy there said they’re no longer made too.