Control panel powers down

This treadmill has recently started behaving abnormally. What I see on power up is the LCDs display all segments and the 3 LEDs all display correctly for perhaps a second, apparently a power-up self test, then everything goes dark. The pushbuttons don't respond.

So far I've checked:

1. The power board under the unit. All LEDs display as per the online repair manual, and the speed LED blinks when I move the motor.

2. The cable from the power board to the control panel has full continuity.

3. There is no documentation on the keyboard, but I was able to determine that they're capacitive, and I got good readings (e.g., noticeable capacitance change) from the ones I could trace. (all but two -- power and program, and I think I nailed those also)

4. Voltage out of the regulators was good on the control panel. The three electrolytics on the board had solid 12V, 5V, and 5V.

5. The magnetic safety switch works fine.

6. The so-and-sos who built the control panel obliterated the markings on all but two of the 9 chips, so reverse engineering wasn't possible.

My gut feel is that during the power-on self test the unit discovers an abnormal state and shuts down, but I don't have enough information to take it from there. For example, a breakout of the signals on the above mentioned cable would be useful.

Naturally the online repair manual wants me to replace boards, but homey don' play dat. Besides, this is an old unit, and parts are unavailable.

Any help appreciated. Thanks!

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Hi there,

Sounds like you've had the unit during normal operations so it seems silly, but that safety key is installed and the magnetic reed switch, in most cases, works with the key installed, as some units power-up, splash version, check for safety key...

If key is good and voltages measured ok I might consider replacing the electrolytics and message me if you need values, most upper boards get a raw or regulated +12 from the lower control board and breaks off the +5v from this +12v. Input to LM7805 say 470uf to 1000uf at 16v-25v.

Regulated +5v out on pin 3 use 470uf to 1000uf at 10v-16v.

Keypad should be resistive "membranes" that actuate a "matrix" key input array for I/O to CPU.

Try carefully removing keypad connections from upper board and restart treadmill, watching for same failure.

Also with a voltmeter, carefully watch that +12v you found when that tread tries to boot-up, as I have seen many cases where that voltage "appears good" but under loading or full display, or certain programs, that power could dip, and a dip to under 11vdc can disrupt +12v biased parts/ICs on the upper causing odd behavior. .... Good luck

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