D
David Nugent
- Jan 1, 1970
- 0
I have a controller out of a moisture oven. It is about 20 years old, and I
need to get it working. It has a digital set point (temperature you want
the oven to go to). When the oven reaches the set point, it is supposed to
turn off (stop heating). I have no schematic for the controller, but have
created a schematic of the area in where I believe the problem lies.
There is a LED that says (Heating when Lit). When the oven is heating up,
the LED stays on. When it reaches the preset temperature, the LED starts to
flicker and then goes out. So I believe the logic side of the controller is
working fine.
The oven element is controlled by a TRIAC (Which is tested ok). It heats up
ok, and if I disconnect the Gate lead, the temperature starts to drop.
There is an "Unknown device" I've posted a picture of before. Maybe in the
schematic, it will make more sense to someone. I'm guessing it's some sort
of opto-isolator, but it's quite large about 2" long, 1" high and 1/2" wide.
A few things I noted/tried:
Out of circuit, pins 3/4 on unknown device look "open" (Meter flashes
infinite resistance). However, if pins 3/4 are not connected to the circuit
(While pins 1& 2 are), the oven will not heat. This puzzled me.
I figured it it was "open" that it would make no difference if it was there.
Disconnected the gate of triac while the oven was heating. Oven started to
drop temperature (Show that triac turns on and off).
As a mention of note: The oven originally had a Q4025P triac (That was
shorted - Oven always on/heating). I was given a BCR16HM triac from a local
electronics supplier and told it would be a fine replacement (Actually looks
a little more heavy duty).
Here is a curious point. When I first discovered the original Triac was
shorted, and replaced it with the new one, the first time the oven powered
up, it worked. It reached it's temperature and then the triac turned off.
But since then, it hasn't worked properly. As I mentioned I rechecked the
new triac and it seems fine.
I would greatly appreciate any help suggestions anyone can give me. I'm
pretty stumped at this point.
Thanks,
Dave
need to get it working. It has a digital set point (temperature you want
the oven to go to). When the oven reaches the set point, it is supposed to
turn off (stop heating). I have no schematic for the controller, but have
created a schematic of the area in where I believe the problem lies.
There is a LED that says (Heating when Lit). When the oven is heating up,
the LED stays on. When it reaches the preset temperature, the LED starts to
flicker and then goes out. So I believe the logic side of the controller is
working fine.
The oven element is controlled by a TRIAC (Which is tested ok). It heats up
ok, and if I disconnect the Gate lead, the temperature starts to drop.
There is an "Unknown device" I've posted a picture of before. Maybe in the
schematic, it will make more sense to someone. I'm guessing it's some sort
of opto-isolator, but it's quite large about 2" long, 1" high and 1/2" wide.
A few things I noted/tried:
Out of circuit, pins 3/4 on unknown device look "open" (Meter flashes
infinite resistance). However, if pins 3/4 are not connected to the circuit
(While pins 1& 2 are), the oven will not heat. This puzzled me.
I figured it it was "open" that it would make no difference if it was there.
Disconnected the gate of triac while the oven was heating. Oven started to
drop temperature (Show that triac turns on and off).
As a mention of note: The oven originally had a Q4025P triac (That was
shorted - Oven always on/heating). I was given a BCR16HM triac from a local
electronics supplier and told it would be a fine replacement (Actually looks
a little more heavy duty).
Here is a curious point. When I first discovered the original Triac was
shorted, and replaced it with the new one, the first time the oven powered
up, it worked. It reached it's temperature and then the triac turned off.
But since then, it hasn't worked properly. As I mentioned I rechecked the
new triac and it seems fine.
I would greatly appreciate any help suggestions anyone can give me. I'm
pretty stumped at this point.
Thanks,
Dave