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Author Topic: SDA /SDT Generator Manual copy available and question on de-magnetised generator  (Read 778 times)

Alexdick

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Hi Rob
I flashed the thing shown in the photos which I think is the rheostat? I may have sparked it a little bit too much?!
Anyway, the light i refer to is in the house about 30m from the generator so a little bit of electricity is getting there from the generator but clearly not much as it is very dim. Any ideas? Should
I try and flash the rheostat again?
Thanks
Alex

mike90045

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If you are even getting a tiny bit of voltage, when you had none before, the flash was successful. Now there is something else preventing the voltage from becoming full. 
 Did you have any loads on the system when you shut it down again ? 

 Let it "build" voltage for a minute or 2 before you engage the breakers and loads.

ajaffa1

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Hi Alex. you need to flash the field not the rheostat. You need to connect your battery to the two wires connected to the rheostat after disconnecting one wire from the rheostat. This will cause electricity to flow through the selenium rectifier into the field windings and magnetize the iron core it is made of.

If that doesn`t work we will have to try and flash the main windings. Something I am hesitant to do because getting the polarity wrong could cause serious damage or injury.

Bob

ajaffa1

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Hi Alex, further to my previous post please ensure that all loads are isolated from the generator when attempting to flash the auxiliary field. You don`t want to feed 12 volt DC into your house.

Bob

Alexdick

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Bob
Thanks for this.... you must think I am a total idiot!! I fully understand what I am meant to do now. I hope I didnít damage the rheostat by doing what I did last night? Iíll get on the case when I return from work tonight and let you know how I get on.
Thanks again.
Alex

ajaffa1

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Hi Alex, no I do not think you are a total idiot, I actually think you are a very useful mammal for trying to fix and understand things for yourself. Most people would phone an electrician or go buy a new one.

Good luck,

Bob

Alexdick

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Hi Bob
No joy sadly :(
Alex

ajaffa1

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Hi Alex, I will have to take the covers of my Brush head and take some more photos. I will also get some resistance measurements with a multi meter so we can compare them with yours to try to track down where the problem lies.

When you start your generator, how do you do it? What does your control panel and top box look like? Does the control panel have a wiring diagram pasted to the inside? A couple of photos would be very helpful.

Bob

Alexdick

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Hi Bob

Apologies for the slow reply.
Sadly, no joy last night when I tried....
I start the generator using 2 x 12v batteries.
I attach some photos of the top box....I don't have a control panel? the feed to the house comes out of the top panel and the to the house where there is a junction box Mains - Off - Generator
The light in the house i have mentioned which is the timer on my central heating system still  (next to the junction box) still flickers dimly when I turn the generator on so there is something getting through albeit next to nothing!
Thanks!
Alex

ajaffa1

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H Alex, sorry not to get back to you sooner. I completely forgot that I had a board meeting to attend yesterday. It sound very posh and important being on the board of directors for the local camping and canoeing center. Let me assure you it isn`t. This is a not for profit organisation and all the board members do it for free. We provide outward bound training for kids and etc as well as certificated training for rescue personnel. I spent most of yesterday in meetings and all of today doing the same.

I will try to get some multi meter readings for you in the morning so that you can compare your readings and hopefully we can identify the issue and get it resolved. Do you have a multi meter, or could you borrow one from a neighbor or friend? You could probably pick up a perfectly serviceable one at the local hardware store for 10 to 20 quid. It needs to do volts AC and DC and ohms (resistance)

Thank you for the photographs, I will try to work out some sort of wiring diagram based on them.

I`ll post my reading tomorrow.

Bob

oldgoat

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Looking at the photos I would turf out those old selenium rectifier bridges and replace them with modern silicon bridges probably cost you $30 and save a lot of grief later. If you have a multimeter turn it to ohms and actually see if you have continuity where you are applying your batteries

Alexdick

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H Alex, sorry not to get back to you sooner. I completely forgot that I had a board meeting to attend yesterday. It sound very posh and important being on the board of directors for the local camping and canoeing center. Let me assure you it isn`t. This is a not for profit organisation and all the board members do it for free. We provide outward bound training for kids and etc as well as certificated training for rescue personnel. I spent most of yesterday in meetings and all of today doing the same.

I will try to get some multi meter readings for you in the morning so that you can compare your readings and hopefully we can identify the issue and get it resolved. Do you have a multi meter, or could you borrow one from a neighbor or friend? You could probably pick up a perfectly serviceable one at the local hardware store for 10 to 20 quid. It needs to do volts AC and DC and ohms (resistance)

Thank you for the photographs, I will try to work out some sort of wiring diagram based on them.

I`ll post my reading tomorrow.

Bob
Thanks Bob, I look forward to hearing from you. I have a multi-meter ready! See pic...

Alexdick

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Looking at the photos I would turf out those old selenium rectifier bridges and replace them with modern silicon bridges probably cost you $30 and save a lot of grief later. If you have a multimeter turn it to ohms and actually see if you have continuity where you are applying your batteries

Thanks, will check later

ajaffa1

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Hi Alex, please see the revised wiring diagram attached.

What I would like for you to do is isolate the generator from the house. Set your multi meter to ohms, place the black probe on the terminal for the black wire in the connector block and the red probe on the terminal for the red wire in the connector block. Please tell me how may ohms it reads. (mine reads 12 ohms)

Bob

Alexdick

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With the ohms set to 2k it reads 0.07 and with it set to 20k it reads zero .this is on the red and black terminals in the top box.

As an aside the  batteries are set to deliver 12v not 24v