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Onan 300-3056 control board repair

MJSchwartz504

Aug 27, 2013
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Hi, First post!

I have an Onan generator that I am trying to repair. While searching the internet trying to find a schematic to aid me in repairing my control board I stumbled across a thread on this site

https://www.electronicspoint.com/onan-control-board-t250748.html

In which another member had posted about the same board. After reading through and looking at the photos from the other post, and seeing they are almost identical,I was hoping to get the same attention to my issue. I have repaired small electronics in the past but Im no wiz. I have attached photos of the board, the problem areas seem to be CR2 and CR3.

Thanks in advance
-Michael
 

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Last edited:

davenn

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Sep 5, 2009
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hi there
welcome to the forums :)

give the board a good wash with hot soapy water and a paint brush ( its soft and gentle) then leave it to fully dry out
You will have some fun swapping any components as you can see there's a nice layer of silicon type sealer over the board

what tests have you done that led you to believe that the problem may lie with those two diodes ?

Dave
 

MJSchwartz504

Aug 27, 2013
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what tests have you done that led you to believe that the problem may lie with those two diodes ?

Thanks for the welcome Dave. If you check out the photos you can see that those two diodes are completely obliterated. One is next to the yellow component and one is next to the switch. I am going to need help identifying what to replace them with and the direction in which they need installed.

-Michael
 

davenn

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Sep 5, 2009
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Hi Michael,

sorry .... I was drawn to the 2 diodes in the centre of the board

OK since you cant make anything out of them any more, use your side cutters and nip them out of the circuit do a gentle board cleanup as I suggested earlier paying good attention to those 2 diode locations be gentle and hopefully at least you should be able to identify which way around the diodes are orientated

then we will have to try and figure out the purpose of those 2 diodes.
that yellow thing is a relay and I suspect the 2 black things are relays as well
its probably that least that diode beside the yellow relay is across the coil of the yellow or the black relay to its right for back EMF protection ... If so a 1N4001 will probably suffice.
The diode beside the switch, Im not sure ... would need to see more of the circuit in that area and how the diode is connected into it.

just a hint ... to save confusion in the future ... put a pic in to paintbrush and put a Yellow circle around the parts being referring to ....
I didnt even see them as components, just more muck on the board ;)

cheers
Dave
 

MJSchwartz504

Aug 27, 2013
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I will get the board cleaned up after I have my coffee. I will post some pictures if I get any better shots of the blown components. I was really hoping to be able to gleam some information about what these components were from the other thread. In that thread the OP replaced the same components on his identical board. On his board it seems that the blown components were both

J1N5552AKK

As far as the the purpose of this circuit. When the start button on the board is depressed it should be sending a 12v signal to the starter solenoid. When the button is depressed now, I am reading some amperage draw from the battery from the board but im not getting the signal voltage at the solenoid.
 
Last edited:

MJSchwartz504

Aug 27, 2013
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After having my cup of coffee I looked over the board. I removed the two bad diodes and on the underside of one i could clearly read 555 and on the other I could just barely make out N55.

I am now pretty much sold on the idea that the offending components were originally J1N5552AKK

on the other post the suggested replacement was 1N5406. Using this as a guide http://www.vishay.com/docs/88516/1n5400.pdf I was wondering if I could use a 1N5404. The generator is only rated to produce 120v.
 

KrisBlueNZ

Sadly passed away in 2015
Nov 28, 2011
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The 1N5552 is available from Element 14.
A 1N5406 would be a lot cheaper but its leads might be too thick to fit through the holes.
Even though the generator's output voltage is only 120V there may be higher voltages at other parts of the circuit, so I would not use a 1N5404. The original was rated for 600V (there's a data sheet at http://www.newark.com/pdfs/datasheets/SSI/10P5274.pdf).

Edit:
Cool!
 
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