EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: CatalinaWOW on July 19, 2019, 04:24:44 am
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One of the things I have acquired is an Adams-Maxwell 1201 Bobbin Winder that is missing the foot pedal speed control. My initial plan for repair of this was to adapt a sewing machine triac controlled foot pedal to the job. The first clue that this would not be easy is the 17 pin circular connector dedicated to the foot pedal.
Adams-Maxwell is still in business and I can literally buy a replacement pedal, but where is the fun in that? I am also afraid to ask the price of said pedal as they do not post prices on line. It seems likely that their price will exceed my hobby needs for a coil winder.
I have been unable to find schematics for this unit online although the manual is available. When powered on the control and counter circuitry all appear to be operating properly, accepting programming instructions per the manual and properly counting turns when the spindle is turned manually.
I have reverse engineered the loose wiring under the deck and this is included in the attached pictures. There are two circuit boards, both are difficult to access and I am reluctant at this time to tear this thing apart. Connections to these cards are through wire bundles that attach to the terminal strip shown in the bottom view. In the schematic attached the circular test points and labels are taken from the attachment to the closer of the two circuit cards.
My questions? First, does anybody have more information on this unit that can be shared.
The other questions relate to possible paths forward. From the schematic you can see that the field current to the motor is fixed, while the armature current is varied by a combination of a front panel switch that selects various taps on a transformer and the foot pedal. The transformer supplies one input of a bridge rectifier, while the foot pedal modifies the return path at the other input of the bridge rectifier. I have been assuming that this modification is some form of phase control via a triac type circuit, but the variable and low AC voltages involved cause me to question this.
I see three potential paths forward. First do a conventional triac control, possibly using the full line voltage in the trigger circuitry to avoid the low voltage problems. Second, I could just hook the bridge directly across the tapped voltage and do PWM on the resulting DC. Finally, there may be nice integrated solutions to this sort of problem. Not my end of electronics and I would welcome suggestions.
Any recommendations on which way to go?
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I have a buddy just down the road that has a business making custom walwarts and he winds all his own transformers for SMPS and linear PSU's. He has a few winding machines so I'll see if he has an Adams-Maxwell or any info on them.......gimme a few days.....ask me in a week as a reminder if I haven't come back with anything.
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I girded my loins and contacted Adams-Maxwell. I must comment that their response was immediate and professional. If any of you have business use for their products I have no problem recommending them for these qualities. However my fears were realized. They will happily ship a replacement foot pedal for $295 US (shipping may or may not be included in that figure). This significantly exceeds what I have invested in this device and may exceed my commitment to have a coil winder for hobby use since I already have a lathe and can easily rig a turns counter.
Thanks for the response tautech. I will probably not proceed until I have heard any further information you may have.
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@CatalinaWOW
Haven't had the chance to visit my buddy yet and have another thing to see him now about for another member too.
Thanks for the reminder post and hope to have something for you in the next couple of days.
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@CatalinaWOW
My buddy knows of this brand but no more.
However he has a Swiss winder that the treadle has failed so has converted it to Variac control.
His tips.
Identify the motor power requirements and work from there.
Voltage, AC or DC.
Convert to bench mounted Variac control and always start lowest speed. Incorporate ON/OFF switching.
Other winder circuitry can be powered independently, counter, rpm, etc.
So while you may not regain all the functionality of this winder for hobbyist use it will be suitable for purpose.
Good luck.
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I don't see any wire tension control. Ones I seen/repaired from the 60's maybe 50's had a s electable weight bouncing up and down between spaced selenium "electric eyes". I think I have an electric eye sensor assembly. Time for ebay.