Treadmill hit with power surge

[xTomtom]

Hi everyone,

Recently I acquired a treadmill that was hit by a power surge (I assume). On the control board, there was a varistor that was blown apart and two traces that were partially blown out. I replaced the varistor (to my knowledge it is a matching one) and wired back where the traces were with some 22 awg solid copper wire. When I went to power it on, still nothing. On a quick inspection with my meter, I was getting incoming voltage on the AC in terminal.

The board is a MC2100LS-30 treadmill controller.

Visibly, there are no other problems. I am wondering what some other things I could check that may have been damaged in the surge. Attached will be some pictures.

Thanks!

[stj]

Re: Treadmill hit with power surge

check for dc leaving the bridge rectifier and check the big gray resistors

[xTomtom]

Re: Treadmill hit with power surge

I checked DC leaving bridge rectifier, roughly around 80V on both the + and - legs. I also checked every resistor on the board and resistance matched what the bands on the resistors said. Any other ideas?

[stj]

Re: Treadmill hit with power surge

80v?
if your mains is 120v ac then the rectifier should output around 160-170v dc

[CapLeaker]

Re: Treadmill hit with power surge

Either you measured wrong, the battery is getting low in your DMM, or that DMM is toasted.

[stj]

Re: Treadmill hit with power surge

or the rectifier has some open diodes.

[xTomtom]

Re: Treadmill hit with power surge

Sorry, maybe I phrased my statement wrong. With reference to ground, the positive DC leg of the bridge rectifier was approx +80 VDC. The negative DC leg of the bridge rectifier was approx -80 VDC. Measured across the DC terminals of the bridge rectifier, my total voltage is approx 170 VDC. I don’t think the problem is there unless I am misunderstanding and there needs to be ~160 VDC off of each leg with reference to ground.

[xTomtom]

Re: Treadmill hit with power surge

Poking around with it tonight I found that this transformer (I think that's what it is) had no voltage coming out on the secondary side and looked kind of melted on the underside. I couldn't see until I got it unsoldered. Going to try to identify the part and see if I can find a replacement.

[CapLeaker]

Re: Treadmill hit with power surge

Your DC ground reference on the primary side of a power supply is always the negative post on the main filter capacitor. So when you measure from any of the main filter capacitor legs to chassis ground, you are using the wrong GND. The voltage across the DC side of the bridge rectifier being at 170VDC is o.k.

Next to the pink resistor looks like a TO220 device probably something similar like a TOP247YN with 5 legs mounted to a heat sink. Replace it.

[sam_sam_sam]

Re: Treadmill hit with power surge

CapLeaker

I was thinking the same thing weather or not it was a TOP something device

That why I was asking for both devices “U4” can not read the part number

What is the part number for “U4” also what is the part number for the device that has the heat sink or if you do not want to take the heat sink of how many pins does the device have

[xTomtom]

Re: Treadmill hit with power surge

The number for the part attached to the heat sink is STR G5551. The “u4” device is MOC3052-A.

[xTomtom]

Re: Treadmill hit with power surge

Can anyone identify that transformer?

[stj]

Re: Treadmill hit with power surge

did you check D5?

[CapLeaker]

Re: Treadmill hit with power surge

If the STR G5551 is dead, there won’t be anything happening on the secondary of the transformer.

[xTomtom]

Re: Treadmill hit with power surge

D5 is good. I have ordered STR G5551 and will update when I test it.

[stj]

Re: Treadmill hit with power surge

change the 2 caps near it - incase one is related to it starting up.