This turntable/tonearm combination has been in my collection for over twenty years. I wired the tonearm for stereo because I particularly enjoy using it with the Shure M3D and M7D.
I couldn't find this in any of the Radio Shack Catalogs issued from the late 50s to the early 60s unless it escaped my tired, old eyes.
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| from page 2 of the 1957 Radio Shack Sale Flyer |
However, the A-3 tonearm, which is essentially a Calrad SV12/Musicmaster Model 12/Velvet Touch sibling, was featured in the 1957 sale flyer above.
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| from page 4 of the 1958 Radio Shack Sale Flyer |
This is the Mark 7 turntable recorded in the Radio Shack Catalog Vault.
Based on the shape of the chassis, this Mark 7 is perhaps the younger of the two since it looks very similar to the succeeding Mark 8, which I will discuss in a future installment.
DIFFERENCES
Although not quite as heavy and massive as a QRK or Russco, the cast aluminum chassis is very rigid on both units. The earlier MK7 chassis above is configured to accommodate a 9"-10" tonearm, while the later MK7 below was designed as a "motor unit" like the Garrard 301 and 401.
The speed selector linkage to the idler wheel in both are similar, but due to a slight difference in the motor mounting layout, the idler arm and idler wheels are not interchangeable.
SIMILARITIES
Except for the paint color, this hysteresis motor is exactly the same unit fitted to my NEAT P58H, which I covered in Part 2 of this series. Click here for motor servicing information.
The main bearing is an oil lubricated design, which supports a 3-lb. cast aluminum platter.
MODs & TIPs
Before moving on, the younger MK7 depicted above had a serious issue - the motor has a bent rotor spindle!😔 Will I be able to save it by adapting the motor from another Lafayette PK245 (don't ask my wife how many turntables I own 😆) with a warped platter?🤔
While planning the motor transplant, I examined the MK7 idler wheel condition and decided it might be worth rejuvenating.
So I mounted it on a handheld drill, deglazed the rolling surface with 400 grit sandpaper, and soaked it in brake fluid for over a week. This was suggested to me decades ago by a kind soul who visited the Rek-O-Kut Tips page in my old website. It has worked with two other Japanese idler wheels but I've never tried it on a Lenco or Rek O Kut. Back in those days, it was more convenient to just send Lenco and ROK wheels to Ed Crockett, RIP 😞 or Terry Witt 👍, who's still catering to the needs of audio DIYers.
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| The above idler wheel was resurfaced by Gary of VoM. 👍 |
Even if the rubber motor mounts were still supple, I replaced them with springs. A nice lesson I learned from servicing my NEAT P58H.
To my ears, the spring mounted motor + 8 mm ball bearing/nylon countersunk washer thrust pad help lower the noise floor.
Realistic Mark 7 stepped pulley specs
Dynax P-9
It is essentially the Realistic Mark 7 above with a different inscription on the badge.
MUSIC VIDEOS 😉
I have a close affinity for the Mark-7 + A3 since this was the very first Japanese idler-driven turntable I acquired.
Always love your posts! I have the Russco Cue Master with a MicroTrack Tonearm. Making slow progress restoring it. Definitely fun machines.
ReplyDeleteThanks for the note!
DeleteEnjoy your restoration project!😊