That’s just the PSU - you need the board inside the MK2A chassis. Remember on the MK3 the external box is not just the PSU but the entirety of control. There’s nothing inside the motor chassis except a breakout board with a few transistor and diode on it for the brakes and strobe and buttons.
That makes sense, thanks. Obviously I haven't studied the schematic in any detail yet. So I'd like to find a parts only Mk2A if possible (or SL1300/1400/1500). Would I be able to use the board from one of those donors or would they just supply the ICs? Certainly the SL1300, etc. would be less expensive than SP-10Mk2A.
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This photo is very helpful. Does it have the improved output stage needed to avoid hand-starting? This is very encouraging - so I will purchase the Mk3 if still available. Do you have any interest in selling the board in that photo? I assume it would benefit from you MN6042 replacement.
No, this is just the stock board with the mating connector for the MK3 motor attached - https://www.mouser.com/ProductDetail/656-SRCN2A2524S.
SL-1300/1400/1500MK2 (SL) uses one 20V rail for the motor, so it's driven with a virtual center for +/-10V approximately. SP-10MK2A (MK2A) does a bit better with a 32V supply, but is still virtual center so +/-15V. On the MK2A there are level-shifters on the P side. The MK3 has +/-32V supplies so the motor drive is +/-32V - double what the MK2A will swing. Of course levels-shifters for both P and N on that one.
The other benefit of the MK2A is that it has all the same adjustments as the MK3, while the SL platform doesn't. The if the MK2A isn't strong enough to command the motor for your situation then I'd look at replicating the MK3 output stage on a breadboard and integrating it on to the MK2A board, but it may just be good enough "out of the box".
The SL platforms aren't known for having MN6042 issues - only the SP-15 and MK3. It was hypothesized that the issues are due to poor or no gate protection on an early MOS design. That could very well be as I think the largest practical difference between the platforms is environmental - people don't tend to use the ground lug on the motor chassis for the SP-15 or MK3, whereas on the SL's it's connected to the arm/phono ground internally.
SL-1300/1400/1500MK2 (SL) uses one 20V rail for the motor, so it's driven with a virtual center for +/-10V approximately. SP-10MK2A (MK2A) does a bit better with a 32V supply, but is still virtual center so +/-15V. On the MK2A there are level-shifters on the P side. The MK3 has +/-32V supplies so the motor drive is +/-32V - double what the MK2A will swing. Of course levels-shifters for both P and N on that one.
The other benefit of the MK2A is that it has all the same adjustments as the MK3, while the SL platform doesn't. The if the MK2A isn't strong enough to command the motor for your situation then I'd look at replicating the MK3 output stage on a breadboard and integrating it on to the MK2A board, but it may just be good enough "out of the box".
The SL platforms aren't known for having MN6042 issues - only the SP-15 and MK3. It was hypothesized that the issues are due to poor or no gate protection on an early MOS design. That could very well be as I think the largest practical difference between the platforms is environmental - people don't tend to use the ground lug on the motor chassis for the SP-15 or MK3, whereas on the SL's it's connected to the arm/phono ground internally.
OK, time for a subjective question. Before I launch into an interesting science project, I'd be interested in opinions about the Mk 3 compared to Mk 2. I have a restored Mk 2 with Graham B44 arm and really like it. The Mk3 will cost several multiples of what I have invested in the Mk 2 so my questions is "Is it worth it?" I realize the Mk 3 is technically superior and has better specs, but are those differences audible. Of course I realize I'm asking for opinions and that's just fine. Many of the people on this thread are true experts with both machines so your opinions are quite valuable to me. Cheers.
"It’s the same chipset as the SL-1300/1400/1500MK2, SP-15, and SP-10MK2A sans pitch control. You could use one of those as a base and hang a beefier output stage for the drive phases."
I don't get the whole pitch control thing. There is only one perfect pitch. I thought the whole purpose behind the Mk2 electronics was to lock in the speed control. Why would you want it adjustable? Why not just have the electronics do it? Most people don't have perfect pitch anyway (I'm certainly one of them) so it would never be right if they fiddled with it.
I just don't get it. Am I wrong thinking my Mk 2's are running at the correct speed if S & T are dead on?
Don
I don't get the whole pitch control thing. There is only one perfect pitch. I thought the whole purpose behind the Mk2 electronics was to lock in the speed control. Why would you want it adjustable? Why not just have the electronics do it? Most people don't have perfect pitch anyway (I'm certainly one of them) so it would never be right if they fiddled with it.
I just don't get it. Am I wrong thinking my Mk 2's are running at the correct speed if S & T are dead on?
Don
The turntables that have pitch control give the ability to adjust said pitch if you want to. (Obviously you don't have to…)
Applications may include;
Matching the rhythm of two different albums when needing to sync in a DJ style.
’Tuning’ the pitch of a recording if playing back whilst playing an actual instrument.
Adjusting a playback for proper pitch if the original recording was mastered or cut off speed.
And the like.
Non-quartz PLL turntables used an LR tank to make an oscillation that the motor drive would follow - but being passive, there are variations in frequency that are temperature and voltage dependent, leading to the necessity of adjusting them to the accurate speed that day but looking at the strobe and getting the platter dots to be still.
This adjustment on a quartz-reference turntable is not required like it was on the non-quartz. But the ability to do so was straightforward to include and an easy bell and whistle to include on the spec sheet.
Those that need it, most notably DJ’s, will obviously want it. This is also an extremely important feature for the archivist market. (Which appears to be dominated by SP-15, interestingly…)
Also, in context of what JP was talking about, the chipset of the SL-1300/1400/1500MK2, SP-15, and SP-10MK2A are all the same, and pitch control is a feature that is separate, so you wouldn’t need to include it if you don't want to.
Applications may include;
Matching the rhythm of two different albums when needing to sync in a DJ style.
’Tuning’ the pitch of a recording if playing back whilst playing an actual instrument.
Adjusting a playback for proper pitch if the original recording was mastered or cut off speed.
And the like.
Non-quartz PLL turntables used an LR tank to make an oscillation that the motor drive would follow - but being passive, there are variations in frequency that are temperature and voltage dependent, leading to the necessity of adjusting them to the accurate speed that day but looking at the strobe and getting the platter dots to be still.
This adjustment on a quartz-reference turntable is not required like it was on the non-quartz. But the ability to do so was straightforward to include and an easy bell and whistle to include on the spec sheet.
Those that need it, most notably DJ’s, will obviously want it. This is also an extremely important feature for the archivist market. (Which appears to be dominated by SP-15, interestingly…)
Also, in context of what JP was talking about, the chipset of the SL-1300/1400/1500MK2, SP-15, and SP-10MK2A are all the same, and pitch control is a feature that is separate, so you wouldn’t need to include it if you don't want to.
S&T adjust the phase relationship of the PLL - have nothing to do with speed. You want it to be approximately 1/3 to be well safe from overshoot causing it to fall out of lock and also to leave plenty of margin for heavy load causing it to also fall out of lock. Not remotely critical.
Pitch adjustment is critical if you play 78s as those are all over the map for speed, and there are speed errors on other records. I use it quite a lot with test records to contrive test signals or identify anomalies in the test record. I have modified one of my MK3 controllers to do -50%, +20% - makes the downstream math easier than 33 vs. 45.
For most people it's likely an unneeded feature.
A lot of them are F/V off the motor with a servo against a reference voltage, the reference not being all that stable.