Re: Two caps instead of 1 ?
Good for you Vince!
Is that a capacitive voltage divider power supply?
Two weeks ago, I repaired am automatic temp control board for a Whirlpool washer. This machine is from the mid 80's and a replacement board is around $110.
It was supposed to modulate either the hot or cold water valve based on the water temp selected for the cycle. Warm is hot valve constantly energized, cold modulated; cold is cold constantly with hot modulated. Unlike 'normal' warm and cold settings, this would assure that 'warm' isn't too hot. And more importantly, that 'cold' wasn't too cold. About 10 years ago, this stopped working- 'warm' was hot & cold continuously, 'cold' was just cold.
I found a service aid better explaining the ckt. I made a little test jig with a pot in place of the thermisor to simulate incoming water temp, and a 4W night light bulb in place of whatever valve was switched by the triac. While playing and probing around, I concluded that the LM339 quad comparator had one of its outputs 'stuck high.' This made the gate driver for the triac bias the triac constantly.
One LM339 and 69 cents later, the board worked again and conformed to the data in the service aid. I got the '339 from ratshack years ago... I also replaced the caps.
-Paul
Good for you Vince!
Is that a capacitive voltage divider power supply?
Two weeks ago, I repaired am automatic temp control board for a Whirlpool washer. This machine is from the mid 80's and a replacement board is around $110.
It was supposed to modulate either the hot or cold water valve based on the water temp selected for the cycle. Warm is hot valve constantly energized, cold modulated; cold is cold constantly with hot modulated. Unlike 'normal' warm and cold settings, this would assure that 'warm' isn't too hot. And more importantly, that 'cold' wasn't too cold. About 10 years ago, this stopped working- 'warm' was hot & cold continuously, 'cold' was just cold.
I found a service aid better explaining the ckt. I made a little test jig with a pot in place of the thermisor to simulate incoming water temp, and a 4W night light bulb in place of whatever valve was switched by the triac. While playing and probing around, I concluded that the LM339 quad comparator had one of its outputs 'stuck high.' This made the gate driver for the triac bias the triac constantly.
One LM339 and 69 cents later, the board worked again and conformed to the data in the service aid. I got the '339 from ratshack years ago... I also replaced the caps.
-Paul
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