Any OPAMP will work fine.Quote:
Originally Posted by Rub87
Edit: you might have to connect pins 1 and 8 together to set the OPAMPS gain to 1 on the LM386
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Any OPAMP will work fine.Quote:
Originally Posted by Rub87
Edit: you might have to connect pins 1 and 8 together to set the OPAMPS gain to 1 on the LM386
What is just the gain function?
I've just tried to breadboard the circuit with an LM386, and I can't get it to work properly.
The gain is the ammount that the input voltage is multiplied by to get the output voltage, and in this circuit it needs to be 1 (so that the voltage set by the pot=Vdimm). The LM386 has an inbuilt gain of 20, which needs to be disabled for it to work in this circuit, but I haven't worked out how do it yet, but I'll keep trying.
Edit: I can't get it to work with an LM386 as it appears to have internal connections to make it into an audio amplifier. :(
Atm I'm trying with an LM358, ripped from and dfi infinity...
An LM358 will work fine :). I've tried with an LM358 and a 741, and both worked ok.
Sorry for my paint skillz, but is it +- like I showed on this pic? (digicam is death, only got webcam)
So this is when the stock pot is removed...
That looks ok. The - input on the OPAMP should be going to the output of the MOSFETs. I've never used a DDR booster before, but that looks like it should work.
The pin were I connect the inv. input of the opamp is the output of the mosfets, not? The middle one comes straight from the +5v and the left one are connected by a very thin interconnect that goes to the middel leg of the pot its also splits to a little 10K smd resitor (R7) (don't know what's that for) so there is only one pin left as output..
The inverting input should be connected to the Vdimm output of the Booster (the 1 remaining pin, sounds like the pin on the right from your description).
The output of the OPAMP should be connected to the point that the middle leg of the pot was removed from (or you could try using the left leg of the MOSFETs, but it shouldn't matter what you use as they should be connected together).
When looking closer at the Booster, there's nothing that regulates the Vbt so that it'll be always the half of Vdimm
Is it possible to disgn the same type of power supllie to keep the vbt half of vdimm?
Could this work out?
Wich type of fet, mosfet? can I use for this purpose?
I'll add some caps here and there...
An IRF640 or IRF630 would work. There aren't any Vtt/Vbt carrying pins on the Dimm slot itself (there's only Vref, which is also 1/2 of Vdimm, but that usually tracks properly on motherboards) so you might have to mod the motherboard itself.
I've done a similar mod on my NF7-s using an OPAMP and an IRF630 MOSFET to make Vbt/Vtt follow.
The LM358 is a dual OPAMP, so you could use the other half to control Vbt.
Quote:
Originally Posted by persivore
I know, thats why I came on the idea to fix the vbt/vtt also :p:
Problem is that the LM358 is kind'a small, this came of an dfi infinity right inder the agp slot.. It's quite vulnerable, but I don't have the equipement to make a pcb for it:/
I'm using the non-SMD/bigger version of the LM358 on my NF7-s, without a PCB. I just glued the OPAMP to the top of the new Vtt MOSFET. It doesn't look very tidy, but it works great!
Yeah, I'll think I'll get monday a bigger version plus some mosfets...Quote:
Originally Posted by persivore
Pffff,
I take a new nf7-s, put the still unmodded booster in, put the power on and the chip under dimm 3 went up in smoke, this pisses me off :frag:
Vref is dead on the board, vbt/vtt is still 1.4v..
It was while vbt/vtt was connected vref...
Now I disconnected vbt/vtt vref and removed the booster, would it be safe to reconnect vbt/vtt to vref as in the 3in1 mod?
I'm not sure how much current Vref draws, but I don't think that it will be much as there is only 1 pin for it on the Dimm pinout. Try doing the Vbt/Vtt to Vref mod, but monitor the voltage as you turn on the board to check that it doesn't go too far out of spec.Quote:
Originally Posted by Rub87
That's the problem, the vbt/vtt=vref mod was done when the vref regulator blew... But I don't knwo why, could it be due the booster?
What could have happened is that Vref followed Vdimm, but Vtt/Vbt didn't, which caused a voltage difference between the 2 regulators and that ended up killing something.
I don't how that could happen as there is nothing that is capable of producing a vbt/vtt that is the half of vref on the booster, goddammit
Vref will usually follow as 1/2 of vdimm. I think that its just produced with a voltage divider from Vdimm to ground, whereas Vtt/Vbt is produced via a regulator.
Yean, but why is vref death and vbt not?
Its on this picture the right regulater that went up in smoke..
I guess that the voltage which could supply the most current was the one that survived. Where are you reading Vtt/Vbt and Vref from?
Vref from the dimm and vbt/vtt from the capacitor...
I find it very strange that Vtt/Vbt has managed to survive, even with a burnt regulator, and Vref has died. Replacing the burnt component might help. Is the Vdimm supply still alive?