Greetings, I've had around 20 of these decks pass through my hands and have 3 complete and one donor in the house at the moment. This are great turntables, very unusual designs, not your standard motor-plank, and have a number unique features.
First off the only part that is NAD is the badge and the green paint, I love NAD but none of their decks are their own design, just rebadged, most recently rega. The 5120 deck was developed in Czechoslovakia at the National Tesla factory and were sold across Czechoslovakia and Hungary under the Tesla brand in a dark colour (model NC470). The designer was an unsung genius called Jiri Janda, who'd built a number of HiFi components at clubs, under the noses of the soviet era authorities. He had to come up with engineering solutions to address their lack of machine tooling,and limited materials common in Western turntable firms.
https://mr-ives.blogspot.com/search?q=NAD
The most unusual thing is the arm which incorporates two additional settings not typically found on other tonearms. The idea is that you can cancel out any arm/cantilever resonance by adjusting the frequency that the balance weight resonantes in a cradle, and how much damping is applied. Its worth spending some time setting these correctly, its free and costs nothing, just time. detailed user guides are available on Vinyl Engine, but the arm can be set in 4 ways:
1) Uses standard values for the two extra settings
2) Use the makers charts that were provided with optimal settings for popular cartridges (circa 1982)
3) Use the calibration test record , only for total completists
4) Find out the parameters needed for new cartridges and follow the guide on how to use the charts to set these.
Getting these right along with the normal tracking and anti skate is about all you need to do
The motors can get noisy, but it's possible to clean and relube them (see link above). Some examples never autoraise at the end, it's just down to whether the peg in the sub-platter is intact.
Other than a motor fail, or a phase cap fail (spins randomly either way, easy fix) they are pretty robust
The earlier models had a flat arm and orange front light, later moving to round arm, red front light and finally suspension adjustment screws from below. With each new variant they improved the internal grounding of the deck, and you tend to find some there is some background hum, buts gets less and less with each model. You can swap arms , so could fit a flat early arm on a later and better plinth, for the ultimate 5120
The decks tend to keep good speed and have a very nice sound. Don't use a slip mat, they don't need one and it will ground out the suspension which hovers very low relative to the plinth top. The originals shipped with a Tesla cartridge, but later in the UK were invariably shipped with an ortofon OM5 or 10 series cartridge. I used one for a while with an OM20 (Any OM body with a STY20 stylus) which cost 4 times more than the deck and gave a lovely sound. In theory you can dial in the parameters of any cartridge and I am amused to see Koetsu cartridges listed in their parameter charts
