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Author Topic: startomatic  (Read 5773 times)

ajaffa1

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Re: startomatic
« Reply #15 on: January 26, 2019, 11:11:47 PM »
John, When selenium rectifiers are failing they start to give off a garlic smell. This is mildly carcinogenic so please don`t take a big lung full. When you start to smell garlic it`s time to swap out the rectifier.

Bob

vegoil

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Re: startomatic
« Reply #16 on: January 27, 2019, 01:49:00 PM »
Hi I have had a ohm meter on it and I get 1.3 ohm each way so am I right it thinking that it is Dead.

cheers

John

BruceM

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Re: startomatic
« Reply #17 on: January 27, 2019, 02:39:21 PM »
Yes, it's kaput; the ohm meter test both ways is reliable. The failed diode caused the cap to fail.

vegoil

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Re: startomatic
« Reply #18 on: January 27, 2019, 05:23:50 PM »
I have ordered the other capacitor the brown one 1uf 250v I suspect it may be blown as well would you be able to tell what way round it goes on the board as there are no + - markings on it. there is a small raised band around the left hand end.  Is it the same as the blue one 50uf 350vDC + to the right hand side. If you look at some of the other photos.

cheers

John

BruceM

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Re: startomatic
« Reply #19 on: January 27, 2019, 05:40:03 PM »
In the diagram there is only one other capacitor, marked "C".  It's only a contact arc suppressor, which is consistent with it being a 1 uF metal film type capacitor.  It's not involved in the diode and larger cap failure. If you do replace it, it must be a metal film type, not an electrolytic.

I don't have a SOM and only have your diagram to go on.  Bob might be able to fill you in better.


vegoil

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Re: startomatic
« Reply #20 on: January 27, 2019, 05:44:53 PM »
thanks for the advice.

Cheers John

ajaffa1

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Re: startomatic
« Reply #21 on: January 27, 2019, 09:39:55 PM »
Hi John, Sorry to see that the old rectifier has turned it`s toes up. That said I wonder how much of our modern electrical equipment will still be working 50+ years from now.

Replacing the rectifier with a diode is an easy fix as is replacing the blown capacitor. Have you checked the resistance of the small solenoid coil? If it is also burned out I can talk you through how to rewind it.

Why do you think the other capacitor is damaged? It is not a part of the same circuit. You can test it with your multi-meter, set it to the lowest Ohms range; now place the black probe to the neutral (orange wire going to small rheostat) and the red probe to the other end. The readout on your meter should briefly scroll as the capacitor charges. If the read out scrolls the capacitor is OK, if it doesn`t, replace it. The negative end is the one connected to the small rheostat (variable resistor).

Bob

vegoil

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Re: startomatic
« Reply #22 on: January 28, 2019, 08:22:00 PM »
Hello Bob,Just got back home, de-soldered the wires from the small capacitor and it is fine. de-soldered the wires from the small coil and it was 100 ohm

cheers

John

ajaffa1

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Re: startomatic
« Reply #23 on: January 28, 2019, 08:34:22 PM »
Hi John, not sure what the resistance should be but if you`ve got continuity it`s probably fine.
looking forward to you having it running again.

Bob

vegoil

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Re: startomatic
« Reply #24 on: January 28, 2019, 08:42:39 PM »
Hello Bob, I made a school boy error, tried to test without de-soldering but quickly realised my error!
I am hoping to have the parts later this week.

Cheers

John

ajaffa1

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Re: startomatic
« Reply #25 on: January 28, 2019, 09:09:06 PM »
Hi John, just went and measured the resistance of my small solenoid coil. I got 106 ohms so I think your reading of 100 ohms is close enough.

Bob

vegoil

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Re: startomatic
« Reply #26 on: January 28, 2019, 09:37:45 PM »
by the way what way round dose the  IN4004 diode go. I mean the silver end to the brown or the yellow wire. just so as I know before it arrives.
again thanks for all the help and advice  without yourself and the forum I would have found this kind of repair very difficult.
you must be very patient having so many people throwing questions at you.

Cheers

John
« Last Edit: January 28, 2019, 09:44:43 PM by vegoil »

ajaffa1

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Re: startomatic
« Reply #27 on: January 28, 2019, 10:20:03 PM »
Hi John, the end of the diode with a silver ring around it is the negative so in your set up the silver ring connects to the yellow and the +ve end to brown. The easiest way to do this is with a terminal connector block screwed to the frame. Something like the photo.

I`m probably the most impatient person you`ll ever meet. I had a very serious car accident just over 2 years ago. I broke my neck and some other bones, had to sit in a chair watching TV for nearly six months. Drove me nearly mad. If I never ever see another episode of Dr Phil or Judge Judy. it`ll be too soon. I eventually got the nod from my doctors saying I could start doing stuff again, so I did and promptly had a heart attack. I now have to be very careful about what I do. If I do too little my neck stiffens up and I loose the use of my hands(trapped nerves), if I do too much I risk another heart attack and my neck stiffens up and I loose the use of my hands. I can`t win. Next month I have to go and see a surgeon about trying to release the nerves.

This forum is the only thing that keeps me sane, I take anti depressants but I find talking people through their mechanical/electrical problems much more therapeutic, so please feel free to ask away. I get huge satisfaction out of helping others do what I no longer can.

Bob

mike90045

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Re: startomatic
« Reply #28 on: January 29, 2019, 04:38:41 AM »
I have ordered the other capacitor the brown one 1uf 250v I suspect it may be blown as well would you be able to tell what way round it goes on the board as there are no + - markings on it. there is a small raised band around the left hand end. ....

It's marked DC working voltage, so I suspect it  is an electrolytic style.

Generally the minus side is marked, arrows, band or whatever.  Perhaps you can check the polarity of the voltage present before you remove it.     Also with such a large value  1uF , it would be unusual for it to be a film or mylar cap without it being very large.  A 250V rating is large, and I would not get a replacement that is any less than that.

BruceM

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Re: startomatic
« Reply #29 on: January 29, 2019, 05:30:13 AM »
As I recall, the 1 uF cap is the one marked C on the schematic, and on the cap it says metal film. As I had already stated.

Electrolytic caps are too high ESR (effective series resistance) to work well for contact arc supression.  There are plenty of DC only rated metal film caps also, they are smaller than the AC ones of similar rated voltage. 1 uF metal film caps for 250VDC are not too big. 

I would not recommend using an electrolytic for this cap C.