Can you identify this resistor?

[mitsu2k]

Came out of a treadmill. It measures 2k however the color bands indicate that it is 9k. I’m puzzled. Can it be that far off?

I’m seeing White, Black, Red, Gold

[redwire]

Re: Can you identify this resistor?

It looks like a carbon comp resistor which are the best for overload/pulse handling (and making smoke lol) yet notorious for drifting with age even +/-20%.
Because of this they are not precision and would follow EIA (lower say E12) standard values. So there are no "9" values in E12 top bands.
I'd guess it was 1kΩ and brown paint on a brown body was having a bad day? It does not look burnt.
It could not be red paint for a 2kΩ part because there is only 1k8 or 2k2 offered.

[mitsu2k]

Re: Can you identify this resistor?

It could not be red paint for a 2kΩ part because there is only 1k8 or 2k2 offered.

Sorry I'm a little confused, are you saying that overall you think this is a 1k resistor even though it is measuring 2k?


Secondly, can I use a metal film 1k 2W resistor in it's place?

[redwire]

Re: Can you identify this resistor?

Resistors typically have huge drops in value only when they get burned up. Wirewound resistors are infallible, they cannot drop in value.
Your carbon-comp part looks fine and oddball value at 9kΩ, that's not an EIA value. I'd expect to see this in an antique CRT TV, so I am suspicious of the markings. But I could be wrong and it's really a white first stripe.

What leads you to believe this part is the problem, treadmills are usually semiconductor/motor failures. A resistor dropping lots in value- usually things still will work. This part could be a cooked resistor but I don't see a bulge or darkened body.

Do you have pics of the board or a model # to see what this part is likely doing.

[mitsu2k]

Re: Can you identify this resistor?

Do you have pics of the board or a model # to see what this part is likely doing.

Here is a pic of the board. That resistor was located right in between the two black relays. You will notice that there was glue that was on the resistor and that resistor got pretty hot because the glue was burnt. I cleaned most of it off. The board keeps blowing one of the output mosfets then a fuse on the motor output side. I had replaced all the caps at the time I replaced the first mosfet although I did not find any caps that were bad in the first place. So new caps, new mosfets, same issue. So to answer your question regarding why I suspect the resistor is because I am very suspicious of the markings and the actual reading which is 2kohms.

Any ideas?

[mitsu2k]

Re: Can you identify this resistor?

Hi @redwire, does that photo help?

[redwire]

Re: Can you identify this resistor?

I can't tell what the resistor is doing, between the relays.
How does this board do braking? It's a half-bridge but so many relays.

Is the big electrolytic capacitor C22 OK, that white glue turns conductive with age, I would scrape it off.
Why is the 12A motor fuse blowing, is the motor OK? I would use a lightbulb limiter and maybe U4 is damaged from when the mosfets blow.

If you want to change the resistor, again I am finding 9kΩ oddball normally you'd use a 10kΩ part metal film is ok.

[mitsu2k]

Re: Can you identify this resistor?

The resistor is connected directly to the switched side of the two relays (common leg of of one and switched leg of the other). I’m not sure what you mean by braking. The motor seems to be fine. Those two big relays are for the motor. I’m assuming the other relays are for the incline which is fine. Yes the big electrolytic is fine.

I do have a 9k on order from digikey but its wire wound. I’m concerned that may not be a good option due to inductance.

Here is a photo if the bottom of the board. Notice the heat signs at the mosfet that blows. That one gets very hot for some reason

I think it’s important to add that the last time I replaced the mosfet it ran good for about 20min before blowing again. I would think if U4 was bad that the mosfet would blow right away or not work at all.

Also check out these. black looks different (maybe lighting) but white is available as first band and this is a 9k.
https://www.ebay.com/itm/11567975532...3ABFBMgMShvtxh

[stj]

Re: Can you identify this resistor?

resolder the transformer - it's starting to stress-crack

[mitsu2k]

Re: Can you identify this resistor?

Hello @stj, thanks for chiming in. I will reflow it as you suggested but I’m not seeing the stress cracks from the photo. Can you point them out for me? If you mean that middle leg on one of the mosfets it's because I burned the pad and had to put an eyelet in.

[sam_sam_sam]

Re: Can you identify this resistor?

When you see rings around the terminal pins is the time to reflow the soldering joints for good measure or at least I would

[mitsu2k]

Re: Can you identify this resistor?

Ok
I got the joints reflowed and a 9k ohm resistor in. On my way to install and test. Wish me luck. Will update on status later. Last time it blew after about 20min. I will run it this time for 40min or so while monitoring current draw from motor.

[mitsu2k]

Re: Can you identify this resistor?

Update: replaced that resistor with a 9k as mentioned above. Ran the treadmill for 45min at various speeds. The most current draw from the motor was about 4.5amps at full speed. Everything seems to be working good. Will continue to monitor for a few days. I also checked tempertaure of the mosftets and they did not exceed 90°F which is way cool. I am just puzzled that the resistor I replaced was that far off in value and not showing any signs of being burned up. Learned something new which is what this is all about. Thanks fir everyone’s help that contributed to this thread.