Taco SR506 circuit board power problem

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Old 01-14-15, 06:13 PM
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Taco SR506 circuit board power problem

I have a taco SR506 circuit board approximately 4 years old. The background: Hydronic coal and oil boilers tied together, with 6 circulators feeding water to different zones. Power to the system comes from panel to a main switch located near heating equipment. The main switch feeds 3 separate switches, the first for the oil boiler, the second for the coal boiler, and the third for the zone board/ circulators. The problem: I have 120v as tested at the input terminals on the sr 506 board, but the green power light is out, so no circulators kick in. It started malfunctioning this way periodically over the last few months with no discernible pattern. I accidentally discovered a temporary fix, which is to turn off the circulator switch, and then turn it back on. This causes the green light to come on and the red lights as well indicating power to the circulators for those zones that need to be satisfied.
A call to the manufacture's rep told me they'd never heard of anything like this before, and that I probably need a new board. Is there anything I can test to replace inexpensively a part as opposed to laying out cash for a new board?
Thanks so much for help. My first post so also let me know if I said/did something wrong here.
 
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Old 01-14-15, 06:41 PM
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Welcome to the forums.

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Is the transformer mounted to the left of the board or on the board itself ?
I'm looking at several different circuit diagrams. The board takes a part of the 24vac from the transformer and converts it to DC for the logic circuitry. That DC is also what runs the green power LED. There really aren't any user serviceable parts in the power supply section.
 
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Old 01-14-15, 07:04 PM
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There really aren't any user serviceable parts in the power supply section.
And Taco doesn't release schematics of their equipment so trying to troubleshoot is an act of 'reverse engineering'.

So even if one did have the skills to work on surface mount electronics, other than finding a bad solder joint somewhere (which is what it sounds like to me) you're pretty much s.o.l.
 
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Old 01-15-15, 05:32 AM
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When the problem arises you may be able to wiggle some of the on board components to see if you could locate a loose joint.
Just a thought
Geo
 
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Old 01-15-15, 10:57 AM
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Pete, The transformer is on the left side on the board itself, attached by two screws. I tried to attach photos, but don't believe I did it successfully.

NJ Trooper and Geochurchi, I was thinking it might be a bad connection or something loose, as was suggested, but the odd part is every time it has happened, 5-6 times over the last few months, it goes back to fully functional if I switch the power from on to off then back to on again. It fixes it without fail 100% of the time. Almost as if the power switch itself is functioning like a reset button. The switch is removed from the board itself, so no vibration to components or circuitry occurs. I will try looking the board over for anything obvious and also try jiggling things.
My thought was perhaps something was eventually heating up, and by the time the house gets cold the bad component has cooled down enough to work. What I fail to grasp though if this is the case, is why it doesn't turn back on automatically upon cool down, since power is available to the board, but instead depends on a manual resetting of the power switch. I probably am sol. Thanks.
 
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Old 01-15-15, 01:40 PM
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That powering off is the Kicker,it almost seems like a relay could be hanging up,but loosing power to the board that doesn't really make sense,I hate to say it but you may be SOL not knowing the circuitry of the board.
Geo
 
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