I just read the phono input section of the Owner's manual and this paragraph explains everything:
For phono 1:
"This input may also be used with cartridges of other types which have lower-than-normal output voltage such as ..... The phono 1 input has a standard input impedance (47K ohms resistance, 100pF capacitance) but is 10 dB more sensitive than phono 2 input"
That's why with the same turntable and cartridge, phono 1 has a higher output level than phono 2 !!
Glad there is nothing wrong with my amp !
Thank you R_J !...
guizmo1967
Senior Member
Last Activity: 01-19-2025, 10:56 PM
Joined: 09-18-2022
Location: Montreal, Quebec
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NAD 3140 phono input mistake !!
Hello,
I accidently connected my aux input (TV) to phono1 and now phono1 is louder (volume higher than phono2).
If I don't touch the volume knob and switch my turntable to phono2, the sound is very good on both but phono2 is just lower than phono1 ???
Do you have any idea why ??
I look at the service manual and there is two 330K resistors connected to ground and to each phono inputs. Do you think that could be one of those resistors ?... -
I ordered five AUO P303-19 but it's gonna take 3-4 weeks for delivery .... Hope they are not fake !!
I will update this thread when I receive it.Leave a comment:
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When I removed Q308, I check with my multimeter just for the heck of it the pads and to my surprise the Gate and Source had continuity even with no mosfet, was this normal ??
I have a question, what should be a good resistance value for the Gate of Q308, that goes to the AUO P303-19
Oh well ! Guess I'll have to order a new AUO P303-19 ......Leave a comment:
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I wanted to check if it was shorted between pins but it slip through my fingers and I lost it !! It was getting really hot when I injected 2V, 1A but I don't think that's over-load ?
Since P303-19 is a DC-DC converter IC, I'm pretty sure that Q301, Q302 and Q308 are all mosfets !
Resistance relative to ground:
Q301
Gate 26MOhms
Source 55KOhms
Drain 75KOhms
Q302
Gate 75KOhms
Source 58KOhms
Drain 0 Ohms
Q308
Gate 3.7 Ohms
Source 0 Ohms
Drain 58KOhms
D301 (tested good...Leave a comment:
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Can someone tell me what is exactly Q302 (W1 marking), another mosfet and if so, part number would be appreciated !
Thank you !Leave a comment:
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Well no luck !! I solder a AP2334GN-HF in place of Q308, put a jumper between Drain and Source of Q9, plug everything back together and no Asus logo ...
Before I made any changes, the screen was always white and now when I turn it on, it goes white a second, then black a second, and white again before stand by (amber light)
I think AUO P303-19 is bad ??...Leave a comment:
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I'm going to try finding a mosfet with marking 12H34 on one of my laptop motherboards that I keep for parts and bridge SOURCE and DRAIN of the P-channel that I don't have yet and see if the Asus logo appears on the screen ??Leave a comment:
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Thank you lotas !
Yes after searching the internet, it is a mosfet. Either P5002CMG like you suggest or AO3400A would do the job !Leave a comment:
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After further investigation, I think it's a SOT-23 NPN transistor. The bottom left is B. bottom right is E and top leg is C.
With no power to the board, the two bottom legs are GND. R302 (Mark 203) keeps Base to ground, transistor OFF.
This transistor is switch ON by AUO-P303-19.Leave a comment:
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I found the problem. I injected +2V, 1A. The area circle in red what getting really hot to the touch, so I thought it was one of those two capacitors. I removed them one at a time and check if the short was gone but no !
Did voltage injection again and it was Q308 that was getting hot !!! Removed that transistor and the short is gone. Soldered back both capacitors and everything is good.
But I think it should be a transistor not a mosfet since there is no G D S markings ?? What do you think....Leave a comment:
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Yes tested with cable disconnected. I connected back the power supply to check what was the voltage at the Source of mosfet Q9 (Of course removed) and it is +12V. Should I start with +3V, 1A or go with +12V, 1A ??
Right now I'm searching online for every IC's on that board to find Vcc pin to make sure none of their power rail is shorted before injecting voltage ....Leave a comment:
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The 12V rail that goes to the T-con is indeed shorted ! There is a lot of capacitor on that board and none are overheated. Don't want to remove capacitor randomly, can you suggest me a way of doing this, not randomly ?
Maybe voltage injection ?
Thank you...Leave a comment:
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Thanks for your reply !
But I figured it out by myself. Q9 is a P-channel mosfet that only switch positive voltage to the connector (I think it's 12V). The gate is pull high by R151, so mosfet is OFF and pull low by NPN transistor Q10, mosfet is ON.
I removed Q9 and check every components around that mosfet and they are all OK.
Unfortunately I don't have a sot-23 P-channel mosfet lying around right now !!
If I'm wrong, don't hesitate to correct me .....
Thank you....Leave a comment:
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Asus VG278 mosfet identification ?
Hello,
My Asus monitor stop working today !! I found the problem on the main board, the power supply board is ok. It's Q9, a mosfet but I have no idea what are the specs since I don't have the schematic for that monitor !!
Can someone help me identified this mosfet ?
Thank you ! -
Possible, maybe ! It's burn through the second layer, I think. How can I solder a new mosfet if there is no more traces, pcb pads ???Leave a comment:
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It's the copper trace that I rolled to the right. Believe me, it is clean !Leave a comment:
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Xbox Series X, is this repairable ??
Hello,
Just look at the pictures and tell me if this Xbox is scrap or repairable ?
I removed the mosfet next to the blown one to see what the traces look like ! Pictures are from top and bottom.
Thank... -
NAD CD/DVD Player T-513 Problem !!
Hello,
I have a NAD T-513 that always display DISC Err, no matter what kind of CD I use.
I change the optical laser pickup, it was only 20$, I had nothing to lose, but it did not solve the problem !
My question is:
On a good working CD player, is the RPM always constant, because on mine, it goes up then down, up then down repeatedly ???
I check the VCC pins of the Motor Drive IC (LA6560) and +8V is present. But one thing I notice, this IC gets hot really fast ???
Do you think LA6560 is bad or the spindle motor ??... -
Well, I'm about to give up on that scope !! After replacing many components, that were probably good, the intensity knob still don't do nothing at all, the line on the screen is at full brightness !!
The intensity modulation (Z-axis) jack at the back is for as I understand it, modulating the brightness of the spot at specific time, correct me if I'm wrong !!
What I did is connect a 100k pot to this jack with a range from -24V to +24V, but nothing happened on the screen no matter how I turned that pot …
The service manual spec says 20 p-p minimum.
...Leave a comment:
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