Hello all. I’ve seen this treadmill board referenced to on this site a few times and have gotten part way through this repair as a result. I’ve had to replace r46 (open) hs1 (g5551) blown and r51 blown. The board has come back to life a little bit. It did actually power the topside control once. LED is not lit and I have 54 volts all over this board in places it really shouldn’t be including at the top of every capacitor except one. I have 54 volts on the output side of the 78l15 and 25 volts in from d4. I can’t visually see any other blown issues. Anyone have any insight to this board?

 

Unfortunately there are many versions o0f this board and the device identifier is different for each, a pic would be an advantage.
Also the generic schematic is on this site if you do a search.
Where are you measuring from?
There is two supplies, one the rectified mains, the other LV derived by either an on board SMPS or a small mains transformer to 12v.

 

I’m pretty sure it’s the newest version, with the SMPS supply. I’ve seen the schematic but it seems it’s considerably different than the one I have. I don’t have a super good understanding of power supplies and this one has a part g5551 that I have never seen and can’t find much info on.

 

OK I pulled a MC2100LS30 off the shelf and HS1 is actually the heat sink, the IC on it is U8 (g5551) is a favorite to go, it is the driver for the SMPS.
If you cannot find a replacement (they are rare) you can wire a small off board linear transformer in a pinch.

 

OK I pulled a MC2100LS30 off the shelf and HS1 is actually the heat sink, the IC on it is U8 (g5551) is a favorite to go, it is the driver for the SMPS.
If you cannot find a replacement (they are rare) you can wire a small off board linear transformer in a pinch.

oh right HS1 heat sink. Lol I read it quick and didn’t think.
I found replacements and replaced it. And the resistors that blew, and it only partially lives now. It was damaged by some water getting on the g5551 initially.

 

Have you got the LV working at least?
The SMPS should be isolated from the mains supply. And be around 12vdc.

 

Have you got the LV working at least?
The SMPS should be isolated from the mains supply. And be around 12vdc.

Yes I have 12-13 volts at the header and it did once power the console.
There’s an audible pulse about 60hz that comes out of the speakers when it fails to power it (like over current/protection??) I have 54 volts on the output side of the 78l15 and 25 volts in on the same parts Input pin from d4.

 

I would remove the 78L15 and see what voltages remain.

 

I would remove the 78L15 and see what voltages remain.

I would remove the 78L15 and see what voltages remain.

I have 23v input side, 54 volts on both the ground pin and output side (ground being the ground spade, and the near ground wire to the heatsink.)

 

I would remove the 78L15 and see what voltages remain.

Looks like I might be learning about this board a bit more (and power supplies in general).
Turns out that the 78l15 I removed to hunt for issues is actually bad.

 

BTW what is the main DC power at the bridge rectifier?

 

BTW what is the main DC power at the bridge rectifier?

I read 110v or so DC on the meter.

 

Thats about right, you should use each respective GND when testing either the LV or HV devices.
The LV is referenced to earth GND through a 10Ω resitor.

 

Thanks for your help! Ive learned something and have ordered parts to see if I can get this going!

 

Well I thought I might have had this. It’s almost alive. Now I get a visual representation of the sounds I heard and the pulsing on my meter.
I can’t post videos now but the LED pulses on and off in a bit of a dramatic fashion. Something is still wrong in the HV section of this board.

 

Is there a repeating pattern to the flash rate of the LED?

 

Is there a repeating pattern to the flash rate of the LED?

Not in a way that it’s controlled by an MCU or anything smart. Kind of haphazardly ramps up to bright then off 2-3 times a second. It’s not in the machine, just on the bench. Maybe it needs to be hooked up?

 

When you power up the board, there should be a pause, then the LED should light steady.
When in a normal run, the LED should flash at a fairly fast steady rate.
Any other problem will show a steady flash of 2 to 6 flashes followed by a pause , e.g. 3 flashes followed by a pause generally indicates the board or motor is drawing excess current.

 

Definately not that. Lol. It’s like the power supply is detecting a fault, shutting down and repeating. I took a 15 volt power supply and supplied it directly to the pads for the 7815 and the led comes on normally and stays solid. Appears that the control section where the MCU is works ok. Seems the 12v SMPS is ok too.

 

Have you checked all the power components on the HS?
The DC ramp SCR , The Mosfet/IGBT, the Mosfet diode,?