Discussion in 'Sega Dreamcast Development and Research' started by Nopileus, Jul 19, 2015.
Thanks works great
Hi guys, randomly found this thread & wanted to share, how you can fake the fan pwm signal, without needing a single additional component! See my recent post on bitbuilt: https://bitbuilt.net/forums/index.php?threads/nolds-alternative-dreamcast-pinouts-workarounds.1822/
You really should disconnect pin 6 on IC601 first (or cut the trace) - with no trigger signal, the Q output will be driven low, and forcing current into the chip might eventually blow up the output driver. The chances of it subsequently catching fire are small, but it could happen.
I did some further research & found out the IC601 is sinking 26mA, which is 6mA above it's max. output sinking current. As you said, the chance is small, but I'll update my graphic with a trace cut!
Installed this one today, ordered the prints and cable from @Collingall, works beautifully. Thanks buddy!
Do you have to break the cable of an original fan to get the connector? or there is other way to get it.
@Collingall, links not working for me, what´s the price? I will not pay more than the price of a full console for a cable, i know retro is expensive, no 3d models? thanks anyway.
You can buy new connectors from digikey.
Preterminated wires: https://www.digikey.com/product-detail/en/6009458
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Weird it works for me. Anyway here are the Digikey part numbers
455-3082-ND preterminated wires
Fyi the wires have the pins terminated on both ends so you only need 2 wires for a single fan cable.
To build the cable yourself you would need the following
3 Pin housing $0.10 each
wire with pins $0.43 each x2
10K resistor $0.10 each
3 pin fan header $0.49 each
so $1.55 plus shipping their lowest priced shipping is $3.75 so you are looking at around $5.30 USD for one cable if you make it yourself that is also if you solder the wires to a pin header. I use nice receptacles in my cables but you can only really find those on Chinese websites like Aliexpress.
I do sell finished cables for $12 on ebay including US shipping or discounted international shipping. If anyone wants to buy one from me direct I will discount them to $10 just send me a dm and we can work out the details.
3D models are avalible in this thread or https://www.thingiverse.com/thing:2308549 I just posted brand new models that are stronger and easier to print on FDM printers.
anyone tried just replacing Dreamcast fan for a new one? In my console sits NMB 1204KL-01W-B49 5V 0.2A and suprisingly, I found plenty of them on Aliexpress. I couldn't resist from ordering one, however when it finally arrived, it turned out that my Dreamcast won't recognise the fan. Moreover, in feedback we can find somebody's review saying that it works with Dreamcast like a charm!
Here's the auction: click
just to verify, the latest v6 https://www.retrorgb.com/updated-dreamcast-noctua-fan-mod-design.html fits fine no need to trim the gdrom metal corner piece anymore?
Correct, you will need to snap off the support clip by the screw hole though. It is only needed for GDEMU installs since the GDROM drive will hold the fan in place when installed.
ok thanks for the clarification
So I'm planning to install the fan mod in my DC over the weekend, but I got a 12v fan, so I can't simply use it's tach line to feed to the DC (I think).
Now, I've got some 555, but I'd prefer a simple solution like quoted above.
Which one is the better solution? I like not having to cut a trace in the IC305 one, but I don't understand how it works, so maybe it has the same issue as the IC601 if you don't cut the trace?
Any pointer is welcome!
Edit: Is using the low noise adapter a good idea with the Noctua A4x10 12V? I guess the airflow would still be more than enough for the DC?
IC305 and IC601 are the two ends of the same signal. The way the circuit works is that it takes the tachometer pulse from the fan and drives a retriggerable monostable with it (IC601) the Q output of that chip is then fed into IC305 to enable the clock. The issue with just pulling it high is that with no tach pulses the Q output will be trying to pull low, so will end up sinking too much current if you just tie it to +3.3V.
If you don't want to cut traces, then just lifting pin 6 on IC601 will have the same effect.
Seems GillBert's post is best. Thanks GillBert! Mind sharing how it works? This could help me assemble slim metal shell with heatsink for Dreamcast without modem, gdrom, power supply or fans.
Really, they are all the same thing - pin 16 of IC301 is connected directly to pin 6 of IC601. IMO, the cleanest version of this mod is the one originally suggested by Megavolt - just remove IC601 completely and install a zero ohm link (or solder blob) across R627 - just pulling the line high with a short to +3.3V has the problem that pin 6 will still be trying to pull it low and will take excessive current trying to drive against a short circuit.
Okay Trimesh. Going to consider other methods but it's too bad it's not as simple as unplugging fan and forgetting about it. Similar problem to removing GDRom drive... Thanks to all for help and guides!
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