VOGONS


Reply 20 of 31, by criz_me

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OK - so just to triple-check - which pins should be connected?

I will go ahead and find GND via the method suggested (minus from HDD molex pin).

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Reply 21 of 31, by pentiumspeed

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You have the answer in front of you. Pull low with low value resistor at first for test from signal to ground. Like 10 ohms for example.

I had same situation with compaq proliant 1500 boards, I had to find correct pin to pull low to prevent fan error on startup.

Cheers,

Great Northern aka Canada.

Reply 22 of 31, by criz_me

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Alright. As you may tell, I am not good at this, and I am trying to avoid frying my "new" CPU 😉

@snufkin You were right. I measured the pins wrong. In fact, the middle pin is connected to the case, so that is GND then. I switched GND and tach, and got a 84 point benchmark. Regarding resistor color coding, I used the multimeter to determine it has exactly 10k Ohm.

@pentiumspeed Following your advice, I added a 10 Ohm resistor (glad I ordered a whole box 😉 ) between the "real" GND now that I know it, and tach. I am running at full 134 points now! Excellent, thank you!

So, as a last step, you are suggesting to connect GND to tach, no resistor in the mix - right?

Reply 23 of 31, by maxtherabbit

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So if you had the pins wrong, why not just try connecting tach from the fan directly to the tach pad without mucking around with resistors or forcing it low?

Reply 25 of 31, by pentiumspeed

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Also 3 pin fans in Dell is same way, ground the signal pin low. For this one I used loop of wire from ground pin to this.

Early OEM eg Proliant 1500, Deskpro XL, etc, computers does not use tach, and is always grounded low and if the fan fail, the signal is allowed to float high. Dell had not used tach on newer chassis (dark grey/odd purple). The ones in beige used tach. Then later on, when PWM fan technologies got introduced, Dell went to 5 pin using rearranged PWM pinout. I used homemade adapter to use standard PWM fan in Dell.

Cheers,

Great Northern aka Canada.

Reply 26 of 31, by criz_me

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Success 😀

See attached, this is what I went with instead of graphite. I now have fan and CPU at 100% speed. Thank you all for your help! Also attached the correct pinout, in case others are looking for it.

Cheers
Christian

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Last edited by criz_me on 2021-04-30, 22:56. Edited 2 times in total.

Reply 27 of 31, by snufkin

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Nice, that should be ok. Only thing I'd worry about would be if the fan stalls you might not know and the CPU might overheat. Could be worth getting a small temp display and attaching the sensor to the heatsink. Something like this (I just did a quick search on ebay):

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Reply 28 of 31, by pentiumspeed

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criz_me wrote on 2021-04-30, 18:18:
Success :) […]
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Success 😀

See attached, this is what I went with instead of graphite. I now have fan and CPU at 100% speed. Thank you all for your help! Also attached the correct pinout, in case others are looking for it.

Cheers
Christian

Please edit that graphic again to prevent misinformation. The overdrive does not use tach, which means to measure rpm (tachometer), correct term I suggest is fan failure signal, normally pulled low when working.

Cheers,

Great Northern aka Canada.

Reply 29 of 31, by Ydee

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@criz_me: I'm sorry about the offtopic, but I have the same mouse as you - Primax and I can't run it in DOS 6.22. If you have it working under this OS, could you please write down what driver you're using? It would be very helpful, thank you.