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Denon SL-7D Direct-Drive Turntable Service & Repair

I’ve just finished repairing and servicing a lovely old deck that one doesn’t often see – a Denon SL-7D direct-drive turntable.

My customer was given the run-around by several techs and wanted me to have a look and see if I could get her going again. This Denon SL-7D came fitted with a gorgeous old AKG P25MD moving iron cartridge – more on that later.

The SL-7D is a great turntable and quite rare – I’d not worked on one before this one. It’s tonearm appears to be oem’d by Jelco and is vewry similar the the Jelco SA-750D.

More information and the owner’s manual can be found at the always excellent Vinyl Engine.

This particular Denon SL-7D had been overhauled at some point a few years ago, but the deck had never worked properly since. The main issue was poor speed control and lack of Quartz lock.

I cleaned the old girl up and then had a good look inside the chassis to start with. The speed controls needed cleaning and lubrication and the spindle bearing contained only a little old, dirty oil, so I fixed that too.

This is how to build a serviceable bearing – removable brass bearing base, complete with thrust pad, fine screw pitch and sealing ‘O’ ring – very nicely done.
Looking from the bottom of the bearing, you can see the steel ball bearing resting in the bearing shaft. I cleaned out the old oil and added fresh synthetic oil.

The guy who worked on this deck previously had seriously goofed though. Rather than take the time to disconnect and desolder the wires leading to each board before he removed the boards to work on them, instead this guy just cut though the wiring looms to each board. When he was done, he just used cheap terminal blocks to reconnect the now broken wiring, a very crude methodology indeed and completely unnecessary in this case.

I’m going to be blunt – there is absolutely no reason to do this, this is an extremely poor decision when the wires could simply have been desoldered from a board.
Again, there was no reason to do this. It is always better to simply desolder wires at one end, but in this case the wiring looms were long enough that you didn’t even need to do this – I was able to gain access to the boards I needed to without having to desolder or disconnect anything!

Thankfully, once I have cleaned everything, checked all the wiring and careful set the deck up again, she worked perfect and played a record very nicely, so this was a great result.

Back to that beautiful old AKG P25MD moving iron cartridge. These things have a super low tracking force of around 1.2g and come with their own individualized frequency response plot like a Denon DL-103 does now for example. Very nice.

Individual frequency response chart for the P25MD cartridge

Summing up, the Denon SL-7D is a really solid direct-drive turntable. She is very well-made, as Denon gear was back then, and the deck sounds great when fitted with a classic period cartridge, like this Audio Technica P25MD. The tonearm is a quality item and operates very nicely. The repair went smoothly and the owner was extremely happy. He actually messaged me to tell me how happy he was with the sound and the fact that I was able to get this lovely deck working for him when others had failed in this regard.

I love it when a customer is happy, especially in relation to vinyl 🙂

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Thanks for reading, leave a comment and let me know what you think!