Mr. Doordoc,

The light relay contacts are not welded. The relay simply picks up as soon
as power is applied and stays picked up from that point.

The up and down relays will operate if I momentarily fake a signal to the
base of the transistors that drive them.

Shorting the up/down switch terminals makes nothing happen whatsoever.

Just how exotic is that proprietary IC on this board, the 16-pin one? There
is another proprietary chip that has only 8 pins. Not sure of its function.

I'm thinking that the IC is bad or else a critical input it needs is not
present. What do you think?

wrote in message
ups.com...

Silver Surfer wrote:
You've given me some good ideas on things to check. Thanks for your
interest in my problem.

Some observations:

The 110V incandescent bulb stays lit all the time.
The board uses three Omron 24V relays to do its thing. One of them is an
open type, and its contacts are in good shape.
On the bench I can't hear any relays operate when shorting the up/down
button terminals.
I don't see any suspicious looking solder joints.
Don't see any burned up or darkened components.
Don't see any cracked or melted circuit board traces.
This opener has no optical safety sensors.
There is a 16-pin integrated circuit on the board made by TI. Cannot
find
the number anywhere on the Web. Called TI. They could not identify it
either and concluded that it was an ASIC.

More questions:

What effect on the circuitry does the optical speed sensor on the motor
shaft have? Does its output need faked with the main board on the bench
for
troubleshooting?
How do the up and down force limiters work?

The revolution counter board (optical speed sensor) is a timing
circuit. The pulses are sent from the counter board to the main logic
board at a uniform rate. So when the door meets an obstruction the
motor slows down, which changes the timing of the pulses & this tells
the opener to stop if the door while opening or stop & reverse while
closing.

So the force limiters set how much the motor has to slow down before
the opener will react to the change in the timing.

If the counter board is bad or not hooked up the opener will run for
exactly 4" in & then stop or stop & reverse back for 4". So for bench
testing the relays should still pull in even though the counter board
isn't connected.

There is 3 relays on the board, one is for open, one is for close, &
the third is for the light. As soon as the opener is plugged in the
light should come on & then time out & shut off. If it stays on all the
time it sounds like the light relay contacts have fused together. If
the open & close relays won't pull in, then either the coils in the
relays are bad, or they are getting power. Check for incoming power to
the relays & trace backwards if they aren't getting power.

DoorDoc
www.DoorsAndOpeners.com