Please Help - Massage chair mainboard failure?

[tunzafun001]

I have a Real Relax Favor 01/ Fortia cloud 9 massage chair that was originally presenting with a fault of not turning on sometimes. Now the remote on/off button lights up, the leds on the mainboard light up, but it doesn't turn on. Tried a replacement remote (wired remote), no change.

Opened it up and discovered something had spilt and dried on to the mainboard at some stage (around the main IC/ crystal area) - see pic.
I cleaned up all the chip legs with IPA. No traces of possible shorts etc any more. Also removed the 8mhz crystal and replaced with another spare I had. Unfortunately no change.
Checked the outgoing 22v AC toroidal transformer, and all it is all good.

Checked the main rectifier, all good. Checked all caps/ diodes/ relays and mosfetts. All seem good..BUT...

There is a small rectangular 4 pin Diode Bridge (DB107s) on the left side near the relays. There is perfect continuity between the the 2 marked AC pins and the -ve DC pin. So I pulled the DB107, but it tested fine. Checked the board, and the short is still there. Removed the orange cap that was in parallel to the marked AC pins. The board still has these locations short.

I then checked each of the 2 pin plugs on the left side (that are marked roller, massage 1, massage 2). So assume they go to the motors etc. Doesn't make sense for both pins to be short?

I asked Real Relax for a wiring diagram/ schematic or to buy a replacement mainboard. No to both.

So started to try and make my own schematic (which is hard as its a 2 sided board, and tracks go under the 6 relays at all angles).
Discovered there is no AC going to the Diode Bridge. The positive and negative pins are fed by the positive and negative from the main rectifier (after passing through a mosfet and relay on the negative side, and via a relay and a diode on the positive side). But I can't be sure, as the short between all 3 pins makes continuity tests/ tracing difficult. Now the usual AC pins are just a loop (with the orange capacitor in between the 2), then a track links off to the negative part of the board.
So it seems this may be an intentional use of a Diode Bridge? Something to do with relay discharge or something?
No resistor nearby, which I think you need for a scrubber setup. Would love some insight here. But again, each of the 2 pin connectors going off to the peripheral motors etc have perfect continuity.

So currently scratching my head. Will solder the bits back on the board tomorrow and check the 5v and 12v regulators on the board.

I did look up the data sheet on the main ROM IC (Sino Wealth SH89F52). I did see there is a reset pin, where you apply voltage to that pin for 10 secs to reset the chip. I assume reset means a chip wipe? Maybe from the spill. Hope not!

Any other suggestions would be greatly appreciated. Cheers

 

[kellys_eye]

Need better, closer images of the board.....

 

[tunzafun001]

Ok. Here are a few more.

One with the Diode Bridge and Cap removed. One put back. One underside of board.

 

[tunzafun001]

Update from testing

AC Input -24v correct

Rectified DC output - 32v sounds about right?

7805 - in 12.1v, out 5v .. correct

LM2576T (was expecting 12v DC out) - This was bit weird. My trusty auto ranging multimeter showed 61v DC out with the 32v in.
Not possibe!! Switched it to AC and it showed 14v. Grabbed a different meter and it showed 12.1v DC. This is first for me and never had this meter let me down before.
So seems like a "messy" 12v output?

Any tips? Maybe a cap on the LM257 feedback line causing a messy 12v out? There is a low ESR 470 uf electrolytic here. Or something else entirely?

Lastly, checked the earlier said weird Diode Bridge setup down the relay/ mosfet end.. 32v DC at + - pins. As expected no voltage at the AC pins. So not used as a AC- DC conversion..

 

[kellys_eye]

So seems like a "messy" 12v output?

Indicative of potentially faulty (or already-failed) capacitor at the LM2576 output.... it would cause 'wonkey' voltages and potentially stop the board doing its thing.

 

[tunzafun001]

Cheers. The caps look fine and test at spec capacitance. But i dont have an esr meter. Lets replace and see.

Will try and sketch out a rough diagram for whatever is going on with that Diode Bridge.

 

[tunzafun001]

Ok..here is the weird diode bridge circuit down the relay end of town.

I also took a photo from above (showing the + side heading off to the diodes).

Photo underneath shows the circuit path from the red cap, through relays, then mosfets, then to the 2 pin loads (marked hot 1, hot2 and roller). Eventually back to +ve in.

Worth mentioning the underside tracks are from the marked AC pins of the Diode Bridge. But its carrying 32v DC, and is a dead short to the common (negative side) of the board. The negative leg of the Diode bridge just connects straight to the common negative.
So basically, the Diode Bridge is just a spectator with only a +ve and 3 negative pins. Again, I have removed the DB107S and it is fully functional.
No idea why?

Can also see the 12V DC supply coming from the left side LM257 going to the relay coils.

Hopefully the diagram and both sides of the board makes sense. My diagram misses the loads coming from the mosfett drain legs. But should still makes sense. The gate side goes off to a series of resistors, transistors etc and ultimately ends up at the IC microcontroller ROM.

 

[kellys_eye]

Opened it up and discovered something had spilt and dried on to the mainboard

If the main processor supply is ok then you might have a dud CPU. Unless you can prove CPU operation you're pretty much fiddling at the edges chasing 'faults' that may only as a result of the CPU not working.

 

[tunzafun001]

Maybe...hope not, as it used to work intermittently. Do you know if a 'reset' means wiping the chip?

Still would like to work out what is going on with Diode Bridge situation as well before giving up.

 

[kellys_eye]

No, a reset won't wipe the chip but it likely won't do anything else anyway as the 'reset' function is implemented every time the equipment powers up.

 

[tunzafun001]

Ah ok, Cheers.
I changed the cap. No change.

Did notice the power button on the remote fades if I push the speed change button. So there must be some form of communication happening from the wired remote as the buttons do have some effect. Dont really know what that means though. A speed adjustment would normally be handled by the mosfets. But no relays are firing.