This is what the bulb looks like at 45rpm. This is with the pot set to 8 volts as stated in the service manual. If I turn the pot down as you say, the motor just comes to a halt!
bulb_zpsteo1drp8.jpg Photo by tsp40 | Photobucket
bulb_zpsteo1drp8.jpg Photo by tsp40 | Photobucket
wow, pretty bright - as said on my unit it doesnt even glow.... it also looks smaller than mine, might be another type of bulb then.
So, if the (AC) voltage is the same for all speeds, then it might be a mechanical issue, after all.....
Sure you did, but is the pulley correctly fixed on the motor?
So, if the (AC) voltage is the same for all speeds, then it might be a mechanical issue, after all.....
Sure you did, but is the pulley correctly fixed on the motor?
This is the bulb at 8 volts as read by the multimeter. 33rpm is 5 volts and 16rpm is 2.5 volts. So obviously the bulb is dimmer on those settings. Will try an oscilloscope next to see if it's a setting up issue.
Borrowed a scope and all speeds are fine and sine wave is good. What I did discover is that the speed slide switch is unreliable. Sometimes to get 45rpm stable I have to move it to 16rpm and then back to 45. I have already taken it apart and cleaned it but will take it apart again and have another look.
glad the issue could be isolated, and I hope you had fun playing with the scope!
This speed slide will be a little difficult, probably not an easy spare part to get.....
good luck!!
This speed slide will be a little difficult, probably not an easy spare part to get.....
good luck!!
Has anyone have any advice on how to make the speed slider more reliable? Sometimes when the speed is off on 45rpm if I press the slider from the bottom so that it is closer to the gold contacts the speed stabilises. I have given it a good clean and sprayed with deoxit G5. Thanks.
That might be difficult, these things are essentially trimpots (just not round...). Once the resistive layer is worn, it will probably go downhill from there. Best would be to find a spare part - you may want to try this guy: homepage fabtech
good luck
good luck
To work out if the speed slider switch is the cause of all my problems then I will need to hardwire the components for 45rpm removing the switch from the equation. Does anyone know what the best way to do this is? I have a Mark 1 board number B 830 225. Thanks.
Carefully clean this switch is all that is needed to reliably him back to work , best with a fiber pencil.
volken
sorry for my last post, I obviously confused the speed adjustment resistor with the selector switch.....
volken is right, some careful cleaning should do the job. otherwise you could replace it with a rotary switch (e.g. from C&K, using a 3x4 version). It will no longer be original but at least you could try and see if all the rest works.
volken is right, some careful cleaning should do the job. otherwise you could replace it with a rotary switch (e.g. from C&K, using a 3x4 version). It will no longer be original but at least you could try and see if all the rest works.
Thanks, have already done that. However, on closer inspection it appears that one of those silver bits of bendy metal is slightly touching the contact next to it for another speed. ie the pad on the end is making contact with the 45rpm speed but is also touching the 33rpm contact lightly. The metal does look a bit damaged and bent so will try and bend it to so that pad on the end is the only thing making contact with the gold points on the board.
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