That would have been great if it was as simple as that. But alas...

Patched 0.01 uF caps:

I tried it with first just the cap on power, then added the second on encoder, but the initial transient noise remails:

After about 10 seconds, those transients are gone:

If it was an issue with the transients, then soft-reset should work, but it doesn't. I'll probably have to pull the MB one day.

I now have transistors Q81, Q77 and fuse F4 on hand. I have my money on the TPCF8104 MOSFET, which is some weird package. I thought it was SOT-28FL, but the width of this package is 2.3 mm, while the TPCF8104 mosfet on the T61 motherboard is 1.5 mm. I had ordered what I thought would be a suitable replacement, without doing sufficient research. I ordered ECH8315-TL-H, but as noted, its width is 0.8 mm wider. It might fit, but some of the pinouts don't quite match. Drain and gate pins line up, but source does not. So scrub that. There is TPCF8104 on eBay, but the price is not worth it.

Anyway, I will be removing the motherboard soon, however I'm not sure how I will power it outside of the laptop case.

OK. So I replaced ALL the components (mosfet, bipolars, fuse, cap, resistor) from a spare T61 board, but it did not help with "fan error". Odd. Could it be that BOTH my replacement fans yield this error? I also have a spare T61 board that I tried my fans on, and they show 'fan error' on boot. So it is probably not the MB afterall.

I had recently replaced the fan in my wife's Thinkpad x201 because it was making so noise. I decided to test this noisy Lenovo original fan on my T61. Guess what? No fan error on boot. Bugger! I didn't know the Lenovos were so fussy about which fans they used. I have since ordered two more fans from different manufacturers.

You could compare the signal for fan rotation of the original vs the replacements. figure out what's different.

>no longer reading the encoder output from the CPU fan. I replaced the CPU fan already, thinking the encoder on the fan stopped working, but apparently not.

>I decided to test this noisy Lenovo original fan on my T61. Guess what? No fan error on boot.

that is a painful and annoying lesson 🙁

rasz_pl wrote on 2023-01-20, 13:54:

>no longer reading the encoder output from the CPU fan. I replaced the CPU fan already, thinking the encoder on the fan stopped working, but apparently not.

>I decided to test this noisy Lenovo original fan on my T61. Guess what? No fan error on boot.

that is a painful and annoying lesson 🙁

Indeed.

Positive to this is that you have the opportunity to use that scope and see what the fan controller is expecting to see from the noisy fan and possibly replicate it, which could help others as well .

Where did you get the replacement fans from? Chinese sellers?

On these thinkpad models of this vintage, the fan is part of the heatsink assembly and is replaced as unit. I know these thinkpads well as I repair and own several.
Yet this fan can be replaced but adhesive tapes get ruined and no longer reusable.

This reason I asked where did you get the fan from, I know chinese sellers sells just the fans and is dodgy quality. Carefully chosen parts from reputable sellers that are not chinese worked well.

Motherboard is *not the issue* as you used old fan and that works means the new fans is not properly tested or low quality before being sold.

The LCD panel has to be replaced. Very brownish and faded. Good panel is bright and clear.

Cheers,

What doesn't add up is that the fan which was in my T61 had been working fine for years, then suddenly fan error after some compressed air cleaning (maybe injured the fan's encoder?), and the replacement also puts out fan error. The replacement fan was from an eBay seller in Canada, but I think is a Chinese fan. The two replacements I ordered, one was from Europe, and the other from the USA.

I don't want to spend any more time on this until those two replacements are in. I've spent a few days on this work already. Removing the motherboard from the case required a lot of time and organisation, not to mix up the screws. There was some other screw ups along the way that I didn't mention.

pentiumspeed, I've had this T61 since 2007. It had served me well. I have always just replaced the fan, not the whole assembly. I usualy use aluminium or copper tape to hold the new fan in place. I've gone through about 5 fans now. Yes, I replaced the LCD 10 years ago. it is not as bright as new, but still usable. My original unit has the Nvidia NV140M, while my spare has the integrated Intel graphics.

Oh yeah right on those screws. You need HMM to keep track of these screws. 😁

I had T61, R61 both failed, got disposed of due to poor design of board. Now I'm down to T60 and modified R52 using T52 board with 9600 GPU, T410 with i7, R51 for USB-floppy duties running XP. I know my friend still owns T500 and is still alive over a decade later running win10, was mine.

Right now, currently not in use right now on these Thinkpads. Due to stupid heatsink poorly designed on later models and same with Dells for weak heatsink and failing boards, so in future going to get HP office type notebook as Elitebook series, already researched.

I'm impressed with IBM designed the T60 for thinness.

Cheers,

I believe I have resolved this issue now. I don't understand why my replacement fan wasn't working, but I suspect some issue with the wiring or encoder itself. When I bought the same brand of fan for my Lenovo x201 (KFTYR brand), and when the system got hot enough for the fan to turn on, it would always turn on for 2 seconds, off 2 seconds, on 2 seconds, off 2 seconds, etc. Although it would cool the CPU sufficiently enough, it was very annoying to use the computer. I ultimately removed it, greased the original fan, and put it back into the x201. No issue.

I fixed the issue with the Lenovo T61 by putting the old fan unit back in, but I think I found the issue. After time, the wires soldered to the encoder board of the fan get loose. it looked like there was a strand of wire on one of the cables touching either the GND or the adjacent solder point. This would explain why when I blew compressed air into the fan, it would sometimes boot up without a fan error - the air moved the wire strand at just the right moment so that it wasn't shorting another contact.

My conclusion, best to avoid these Lenovo fans with the KFTYR branding. I tried to order a fan recently which looked to be from Lenovo brand in the photo, but the seller send a generic.

Blowing compressed air into fans can induce high voltages and damage the fan electronics or outside peripherals. It's like a generator and the transistors have breakthrough voltages...

I would expect there to be some protection from current back flow; is that not the case?

At any rate, there was nothing wrong with the fan. Pulling the three wires off and resoldering was all that was needed.

IBM never used these fans with chinese-sounding fans. Ever. KFTYR branding is fake fan, this is why I asked you to provide photos.

True fans that IBM uses:
Toshiba made fan:
https://www.ebay.ca/itm/195208404229?hash=ite … ABk9SR8714qDDYQ

I had success fitting these heatsink in thinkpad T61 t00.
https://www.ebay.ca/itm/184561045585?hash=ite … ABk9SR9T14qDDYQ

Also you can use this too, fits perfectly.
https://www.ebay.ca/itm/165624444817?hash=ite … ABk9SR5D7jKHDYQ

I have few thinkpad fans I no longer need and works fine, for you to have and I'm in Ontario, Canada.

I started with T500 but rebuilt it from parts as it was cheaper back in about 2011 or 12, didn't remember when. Still working currently owned by my friend in use with windows 10 Pro.

Cheers,

I had been using "fake" fans in my T61 for almost 15 years without issue. It wasn't until I got the KFTYR that it didn't work right. I was able to fix my previous fake fan by resoldering the wires, however, I think ordering one of those complete fan/heatsink units NOS would be a wise move.

There's none NOS now at this moment.

Keep the heatsink and swap the fan. The fans I have are working great and I can lube them first then send to you and are genuine. The one in T500 is used daily had got the treatment when I cleaned the heatsink mid-way the life. I'm sure still working. Most of my notebooks get the fan lubed once I got them apart if I can lift fan rotor off the stator.

Really wanted them out of here and been sitting unused in my storage bin for years.

Cheers,