Do you own a “speedy” Dual turntable? There is a well-known speed issue that affects SM-840 motors installed in specific belt-driven turntable models.
The speed problem is usually fixed by replacing the faulty SM-840 motor with an upgraded SM-860 motor, which are hard to find these days and quite costly.
But wait… Don’t throw out that old “speedy” SM-840 motor! Now there’s a simple fix that can restore your turntable to perfect operation without even removing the old motor: The BumbleBee!
The MSF-60 motor speed fix is a Do-It-Yourself kit, consisting of a tiny circuit board that remediates the speed problem with Dual SM-840 motors operating at 120V AC at 60 Hz. The MSF-60 works with the Dual 1249, 601, 510 and 502 turntables.
Affected turntables exhibit speed instability at startup, namely the 33-1/3 RPM rotation operates at double the speed. This “speed takeoff” occurs randomly and can be affected by any combination of line voltage, line frequency, sine wave phase, and mechanical load on the motor.
HOW IT WORKS:
A tiny microprocessor creates a timing pulse that injects a small load onto the motor for a short interval at startup. The load is controlled by a solid state relay and the circuit is powered by a self-contained miniature power supply. This startup pulse allows the motor enough time to properly synchronize and lock in the speed, thus preventing “speed takeoff”.
The “BumbleBee” modification kit attaches to the underside of the deck plate with the included double-sided gel tape, and installs easily with just three wires. Our easy-to-follow installation manual in PDF format shows you step-by-step wiring guides for each turntable model.
Or, we can install the module for you for a reasonable fee, as well as any other turntable, tube audio, computer and electronic repairs and modifications you may have in the Toronto area.
Please Note: This Do-It-Yourself modification kit is easy to install, but is suited to technically-inclined Dual owners. The kit requires a certain knowledge of electronics to install, as well as soldering and schematic skills and a basic set of tools.
“I finally had the time to install the MSF-60 kit I purchased from you and wanted to let you know how pleased I am with it. I am happy to report that it works like a charm, exactly as claimed. In addition, your directions complete with photos are excellent and very easy to follow. Thank you very much for a solution to a problem which has bugged me for years.”
“I can attest that this board works perfectly, as I have had the pleasure of testing the first pre-production board on a sick 601 I have … I was well pleased with the results and can heartily recommend it!”
Former Assistant Service Manager
Noresco – Dual of Canada
PLACE AN ORDER HERE:
All prices are in Canadian Dollars.
- The MSF-60 kits are $60.00 each
- Flat rate shipping and handling to anywhere in North America is $8.00
1. Please specify your turntable model number in the PayPal instructions box.
2. Please include your phone number (required for U.S. shipping).
After completing the PayPal Checkout process, your item will be dispatched immediately by Canada Post.
We ship by Lettermail to Canada and Small Packet Air to the US. In order to reduce cost, this economy service does not include tracking. Your order will take an average of 2-6 weeks to arrive.
- The “speed takeoff” fault only occurs in 120V AC / 60 Hz model SM-840 motors, mainly from the American continents. The MSF-60 kit will have no effect on 50 Hz motors.
- The MSF-60 kit is specifically designed to remediate the “speed takeoff” fault. It will not fix other SM-840 issues caused by bad bearings, worn parts, bent shafts, etc.
- Proper operation of the MSF-60 kit is predicated on the motor having sufficient mechanical drag. Thus, it is important to use a platter drive belt in new or good condition. Old, worn-out, stretched rubber belts will be too loose and may prevent the MSF from correcting the motor speed each and every time.