Michell prisma circuit board

[22mart0]

Hi all I’m after help
I’m trying to fire up the motor on the prisma all wires and fuses have been checked and board looks good but can anyone tell m3 what this is as no power after.
thank you for your help
also what else do I check/look for

 

[AngrySailor]

Hi all I’m after help
I’m trying to fire up the motor on the prisma all wires and fuses have been checked and board looks good but can anyone tell m3 what this is as no power after.
thank you for your help
also what else do I check/look for

Nice. I’ve got a Prisma also. There’s a thread where I had the whole motor split apart to clean and oil
The bushings. They use a magnetic reed switch, do you have to motor assembled with the magnet on the power knob to engage the switch?

 

[22mart0]

Thank you so much for your reply and help
I have read and enjoyed your post with much interest
lm very much in the dark and very green so…..the motor is still In one piece but feels good, lm I little confused.
I have 240 going to the circuit board and up to the glass thing in the photo even with the switch on but nothing else,
nothing looks to have failed but I will also need to potentiometers when I get power in

ok so understand now that’s called a reed switch and I take it that it’s open …..can I jump it ?

 

[AngrySailor]

Thank you so much for your reply and help
I have read and enjoyed your post with much interest
lm very much in the dark and very green so…..the motor is still In one piece but feels good, lm I little confused.
I have 240 going to the circuit board and up to the glass thing in the photo even with the switch on but nothing else,
nothing looks to have failed but I will also need to potentiometers when I get power in

ok so understand now that’s called a reed switch and I take it that it’s open …..can I jump it ?

It’s been a while since I worked on that so I’m a little fuzzy. There’s that micro switch there also and I don’t remember what it does. You may not want to jump anything as the micro switch and reed switch could work in conjunction. These motors are rare as unicorn piss so try not to hurt it! I would try assembling it enough that the power switch knob is in place, this will let the magnet and the cam on the shaft work both the reed switch and micro switch as intended.

 

[AngrySailor]

ok so understand now that’s called a reed switch and I take it that it’s open …..can I jump it ?

It’s open until the magnet on the power knob closes it. I “THINK” the reed switch is the main power and the micro switch is the 33/45 selector which happens when you turn the knob left or right one way is magnet only and the other is magnet and micro switch. Again if you’re unsure I’d assemble it so it works as intended and test from there.

 

[J!m]

Seems plausible to me, but this is the first I've ever seen these components...

 

[22mart0]

It’s open until the magnet on the power knob closes it. I “THINK” the reed switch is the main power and the micro switch is the 33/45 selector which happens when you turn the knob left or right one way is magnet only and the other is magnet and micro switch. Again if you’re unsure I’d assemble it so it works as intended and test from there.

Thank you I did wonder 33/45 I will try tomorrow and post later thank you for your help

 

[22mart0]

Hi all update, I found the fuse holder to be faulty so now have the light working but no motor I believe the fault to be both potentiometers as both broken , does anyone know where to obtain the same size ones , I also believe both to be 4k7
thank you

 

[J!m]

After trying reputable sources, I ended up going to eBay to get small case 10k (I think they were) pots to replace the trim pots in my Kenwood.

I’ve never heard of a pot near 4K before… tiny board mount trim pot maybe? Still seems an odd value.

 

[22mart0]

Hi Jim thank you for your reply , I’m very green with this so every day is a school day, please see pics one does reed 4k7 the other I’m not sure what do you think?

 

[WOPL Sniffer]

I think that was the old ancient way of marking them. So, 4.7K I believe. Find a suitable sized 5K pot. If in doubt, measure the resistance with your meter to be sure. Are you SURE the old ones are "Both Broken"?????

 

[Gepetto]

I think that was the old ancient way of marking them. So, 4.7K I believe. Find a suitable sized 5K pot. If in doubt, measure the resistance with your meter to be sure. Are you SURE the old ones are "Both Broken"?????

Actually still a well used way of marking resistances. The units replace the decimal point...

2R2 = 2.2
22R = 22
220R = 220
1K5 = 1.5K
and so on.

 

[WOPL Sniffer]

Ancient

 

[22mart0]

I think that was the old ancient way of marking them. So, 4.7K I believe. Find a suitable sized 5K pot. If in doubt, measure the resistance with your meter to be sure. Are you SURE the old ones are "Both Broken"?????

Hi thank you for your help, I have attached a pic of one pot (cracked) the other has outer contact missing + neither are adjusting from knobs

 

[J!m]

5k seems the closest modern pot like Sniff says. I’d try that and see what happens.

Is it also possible that marking is a manufacturing number? Model number or something rather than the rating/value? The other pot seems marked differently which would be very odd indeed. (Not manufacturing friendly)

 

[AngrySailor]

There’s a course trim pot which affects both the 33&45 pot also so the actual value of those trim pots likely has some wiggle room. To me the issue would be trying to keep things visually original. I did repair one of mine with a pencil lead for a wiper. Works fine, I set it in the middle then adjusted the course speed close, set the trim and darn near forget it. The strobe is always spot on, they’re not a pot you will adjust much if ever...

 

[WOPL Sniffer]

There’s a course trim pot which affects both the 33&45 pot also so the actual value of those trim pots likely has some wiggle room. To me the issue would be trying to keep things visually original. I did repair one of mine with a pencil lead for a wiper. Works fine, I set it in the middle then adjusted the course speed close, set the trim and darn near forget it. The strobe is always spot on, they’re not a pot you will adjust much if ever...

Visually original aint gonna work with 2 broken pots. Get over it, sometimes ya gotta do what ya gotta do. Including painting it green.

 

[22mart0]

There’s a course trim pot which affects both the 33&45 pot also so the actual value of those trim pots likely has some wiggle room. To me the issue would be trying to keep things visually original. I did repair one of mine with a pencil lead for a wiper. Works fine, I set it in the middle then adjusted the course speed close, set the trim and darn near forget it. The strobe is always spot on, they’re not a pot you will adjust much if ever...

Hi update I have changed the two pots and light is on but motor still not running I suspect the Trimpot on the board to be the culprit as it’s very black any idea on its value I belive I read some where it’s a 50k?

 

[AngrySailor]

Hi update I have changed the two pots and light is on but motor still not running I suspect the Trimpot on the board to be the culprit as it’s very black any idea on its value I belive I read some where it’s a 50k?

Take a reading across it, spray it with some cleaner and gently work it see if it’s making contact and what it reads. Maybe note where it is roughly now so you can start in the ball park.

 

[22mart0]

Hi update I have changed the two pots and light is on but motor still not running I suspect the Trimpot on the board to be the culprit as it’s very black any idea on its value I belive I read some where it’s a 50k?

New one on order as it all fell apart …..bugger ……and yes it is 50k lin