I had to repair one of these recently, and while searching for answers, there were ~20 threads of people wondering why the platter stopped spinning / tonearm stopped moving, or things would work intermittently. Many threads ended with no conclusion, so I suspect many tables were binned.
I had some time this morning to finish it off and thought I'd share, in case someone does a search in the future.
These points will likely apply to similar Technics turntables like the SL-QD22, SL-BD33, SL-BD20, etc, not just the SL-QD33. It's just a budget table but apparently decent enough.
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- The first major problem is that Technics cheaped out and used Toshin Kogyo capacitors in these (they say TK on them). The particular ones that were bad were ALL the 47uF ones in my unit, down to 10uF or worse in some cases. I took the opportunity to replace them all, but if you are on a budget, I'd recommend replacing all the TK branded ones at least. Check all boards (function button board, power supply board, motor board). Generally the Panasonic/Matsushita (triangle logo) are fine. This will generally restore all electronic function, particularly the platter and tonearm either completely not working or only working intermittently.
- I replaced the main PSU capacitor (2200uF axial) with a slightly higher value 2700uF Panasonic FM radial, you can do whatever you want here - just make sure it physically fits. This one *just* cleared when mounted upright.
- The second "issue" most people notice is that the record size detection "prongs" that poke out of the platter are amiss, and that only one of them is poking up. They mistakenly think this might be a cause of a whole bunch of issues (as did I) - but actually - it's not a problem at all. I think these either broke really easily or were like this from factory (it's just the outer one), either way, if there are problems with your turntable then this isn't it. If neither of them pop up you *should* address it, but if the inner one is poking up and the outer one is down, don't worry about it - all functions of the table will still work normally.
- There are a lot of adjustments that need to be done as per the service manual. You can get them from vinylengine with a free account, the QD33 one is here: https://www.vinylengine.com/library/technics/sl-qd33.shtml
- Something confusing is that there are two adjustments performed through the same hole (under a rubber cap near where the tonearm enters the table). What happens is that when the tonearm is at rest, one screw is positioned under that hole, however when you move the tonearm onto the platter (as per instructions), it moves a different screw under that hole - hence two different adjustments. The other adjustments are straightforward and the manual is excellent - you have to set yourself up so you can work from underneath the table (without turning it upside down) though.
- The entire system is very sensitive to the initial positioning / setup of the parts inside the tonearm positioning mechanism. If the start/stop light flashes when you try to use the turntable, it means there is an error in the initial setting of something in that mechanism. This part is a royal pain, but my advice is just be gentle when you mess around with it so you don't break anything. The arm should be able to move to the center of the record freely from its rest position and back if you've positioned things right, without feeling like it gets "spring loaded" at any point (before you power-on the table).
- If everything works well but the start point or end point detections don't work, it's likely something to do with the initial setting of the plastic mechanisms described in the above point - particularly the plastic parts triggered by the large/small disc tabs on the platter.
- There are some tiny switches in the record size detection mechanism (a triplet of black cable runs to these switch boards from memory), they are depressed at different extremes of operation. If all else fails you can unscrew these boards and check that pressing the switches causes the matching terminals to short (I used my meter in diode test mode). You don't have to desolder anything to test them. Mine were fine.
- My knowledge of turntables is limited, but apparently the stock P-mount cartridge is decent (better than the cheapest replacements anyway), and you can just get a replacement stylus for it. Typing EPS30 or P30 stylus into ebay will get you going. I'm sure there are better cartridges if desired, but I'd replace the stylus on the original as a minimum - the stock one will have deteriorated damping rubber. The purple part just pulls off by hand, very easy.
- The stock hinges suck and the perspex tabs that slot into them are fragile (and probably cracked) so be gentle + remove the lot to work on it, if still intact.
The main problem is the capacitors. The actual mechanisms and motor in these tables seem to be quite reliable if someone hasn't messed around with them already.
This table didn't work at all initially, then after moving things manually occasionally I could get the platter to spin and arm to move a bit but that stopped again. After recapping, everything worked again, however the initial record size detection didn't (arm would move all the way to the middle on start). Then, after pulling apart the arm mechanism and resetting everything carefully, everything works perfectly - including record size detection, start/end points, cueing, and even the repeat function (which is kinda cool!).
Picture of recapped boards (I just used spare parts I had lying around, including a mix of film caps for smaller values):
View attachment 977645
(There's also some more caps to change under the control/button board visible in top left)
I also attached some pictures I saved from the internet of the various mechanisms that operate the arm - just in case people want to check for things like broken plastic tabs. These are not my pictures, I just used them to check for broken parts on the one I was working on (everything seemed to match).
