The Sewing Place

Bernini 707 minimatic

Lachica

Re: Bernini 707 minimatic
« Reply #15 on: April 19, 2018, 09:00:21 AM »
Meter seems to confirm it's working as on/off switch. There is a small amount of resistance change at the very end of the footpedal movement, which makes me think it might be possible to adjust travel on the thumbwheel? @Roger, any thoughts, I think you're also a vintage machine fan?
Mary

Lachica

Re: Bernini 707 minimatic
« Reply #16 on: April 19, 2018, 09:10:29 AM »
@b15erk @Madame Cholet I've just found your comments about 730 foot pedals. Mine was easy to take apart, just 6 screws. No sign of carbon discs and no muck. On the back it says ' Bernina type 200 speed regulator' so I think I've answered my own question, there's a fault. I might do as you did and buy a generic one, if I can be sure it'll work.
Mary

Lachica

Re: Bernini 707 minimatic
« Reply #17 on: April 19, 2018, 09:27:11 AM »
Related question: how does the motor cover come off? Might as well check the max/min switch while I'm at it.
Mary

arrow

Re: Bernini 707 minimatic
« Reply #18 on: April 19, 2018, 11:16:32 AM »
I think there are two screws under the machine, it migh come off on it's own, one some machines I think you have to remove the side panel to get it off.

arrow

Re: Bernini 707 minimatic
« Reply #19 on: April 19, 2018, 12:00:32 PM »
My pedal is slightly different, but the squarish white thing is the cartrige for a stack of carbon disks. The battery like cylinder with a wire out of each end is the capacitor that often needs replacement as the decades go by. They can cause speed issues, machines to run by them selves, blow up with a bang, or just make it all stop running. You can simply remove it and see what happens. (I kept it and showed it to a repair guy and he found a new one). My 730 has the large green metal pedal, my 900 Nova has a round pedal and the carbon resistor is just a tiny solid square bit. I think you might have the type  with one or two stacks of carbon disks.

For speed adjustments you usually try different settings, and the idea is to get an even movement of the parts that move in and out of the cartridge (I'm not sure if its the correct terminology). When you press  the pedal all the way it is suppose to touch the copper conductor parts directly and  bypass the carbon disks. The carbon cartridge slows the current and it gradually increases speed as the pedal go down. From the picture I can't see exactly how it works with the spring action and adjustment nut, but push the pedal and observe how the mechanics work. The game is to find the spot (simply turning the nut to a different position) where the speed gradually increases and as the pedal comes fully down it obviously reaches full speed. I'm not sure if the explanation helps, but it is usually not too difficult for a DIY adustment. On the motor there's a switch for one even speed and another for gradual speed. Make sure you are not testing the pedal on the even speed setting, it should be a nice medium-slow stitching pace however far down you push the pedal. I'm probably just rambling on with all the stuff you know well and are onto already  :P

Is it an original pedal? Berninas can be fuzzy with replacements, even with the basic pedal like this I know some have needed to get both a second and third replacment before it worked. In theory it should be fine, but it's one of those odd things that's happened more than once and I guess that's why some go for the more expensive Bernina brand replacements.
« Last Edit: April 19, 2018, 16:50:24 PM by arrow »

Lachica

Re: Bernini 707 minimatic
« Reply #20 on: April 19, 2018, 13:17:20 PM »
Thanks for your quick reply @arrow. There's only about 4mm of movement on the central rod which goes through this the carbon rheostat. The capacitor looks fine, the wax ends are still intact (haven't seen one like this for decades).

With regard to the max/min switch, thanks for your comment, I'll see if I can get in there. The manual describes it as an 'adjustable motor' with 'min' being half the revs so presumably it switches out half the motor windings.

The pedal does look a bit different to the one shown in the manual, but the photo is of a continental 2 pin plug, mine is obviously made for the British market and has a 3 pin plug.
Mary

Lachica

Re: Bernini 707 minimatic
« Reply #21 on: April 19, 2018, 13:25:25 PM »
Sorted, thanks @arrow. I adjusted the thumbwheel and it now accelerates smoothly. The max/min switch is working, it obviously needed the pedal to be adjusted first.
Mary

Lachica

Re: Bernini 707 minimatic
« Reply #22 on: April 20, 2018, 15:36:53 PM »
Bad news - just done a small amount of stitching, sat in front of machine with foot nowhere near the pedal, and the motor started humming. Next thing it's stitching full speed ahead! Pulled out mains plug, fetched my husband, plugged it back in & off it went all on its own. >:). Took the foot control apart and the end has melted out of the capacitor. I won't be doing any more sewing this holiday unless I can find somewhere to buy a replacement capacitor. And borrow a soldering iron :angry:
Mary

arrow

Re: Bernini 707 minimatic
« Reply #23 on: April 20, 2018, 18:22:07 PM »
Can't you simply cut off or unscrew the capacitor? The only trouble will be TV interference, and  maybe wifi or phone signal interference. It's minimal though. Keep the cylinder and a replacment can be found more easily, at least for an amateur like me.

Lachica

Re: Bernini 707 minimatic
« Reply #24 on: April 20, 2018, 21:30:57 PM »
Yes, @arrow, snipped the capacitor out & carried on stitching. No interference problems, TV and radio are via internet.
Mary