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I have a NAD 272 power amp linked to a NAD T752 A/V amp and have had ** end of problems. Purchased in 2005, 6 months after, the right speaker (Paradigms studio 60) channel would just fade away periodically, and then come back with a thump. Noone (NAD audio repair shop) could initially find any fault but when I powered just thru the 752, there was ** channel drop out.
The 272 was supposedly fixed, (altho NAD still say they could find ** fault)it happened twice again, and last fixed in November 2006. Last week, 6th March 2008, the same problem arose with the left channel. I have taken the CD player out of the equation, problem still existed, DVD player out of the equation, problem still there, the FM tuner in the 752, problem still there. Take the 272 out and put all speakers thru the 752, everything runs fine.
The speakers have been stripped down to ensure ** crossover wires are touching. I run a NAD CD, an OPPO DVD, a Project turntable thru a NAD preamp.
I have hard copies of both manuals, but there are ** specs in the 272 manual!I have hard copies of both manuals, but there are ** specs in the 272 manual!
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Well..this is one for the books. Can you tell me what the ratings are between the 252 and the 752 impedance matching wise? even though it might work sometimes, impedance matching can wreak havoc between mismatched amps.
so, with that noted, there appears to be a jumper change needed(see 752 manual) for using the 752 as a pre amp driving another amp...seems that since the 752 works fine, and the 272 does NOT, that would suggest that perhaps the 752 is over driving the 272 making it clip after a certain amount of time.
try this..run one channel only with them both hooked up, and monitor the heating effect on the 272. the symptoms remind me of a class A amp overheating.
take a close look at the specs on the output characteristics of the 752 to make sure it's not over driving the 272.. so, with that noted, there appears to be a jumper change needed(see 752 manual) for using the 752 as a pre amp driving another amp...seems that since the 752 works fine, and the 272 does NOT, that would suggest that perhaps the 752 is over driving the 272 making it clip after a certain amount of time.
try this..run one channel only with them both hooked up, and monitor the heating effect on the 272. the symptoms remind me of a class A amp overheating.
take a close look at the specs on the output characteristics of the 752 to make sure it's not over driving the 272..
yes..saw that...the key here is why there's a buildup of mismatching, which is causing the fade, and then the whoomph(a classic recovery signal from cutoff in an amplifier)..yes..saw that...the key here is why there's a buildup of mismatching, which is causing the fade, and then the whoomph(a classic recovery signal from cutoff in an amplifier)..
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Hi there I have a C340 that has similar problem, you must have bought this from ebay, lol.
Nad made a mistake on the C range, the pre - power link can be shorted out. if the pre is shorted out it takes out the pre amplifier stage, I have managed to get the right channel working, I will keep you informed what is the cause of the left channel. I have replaced the pre-amp IC and a couple of Jfets and transistors. Once I have repaired the Amp I could repaire yours if you like???
It could be entering protect mode because it has no speakers wired to it, have you tried connecting to all 6 speaker - out connections. Often, if an amp can't detect a load on all 6 channels it won't work. Also, have you checked the thermal fuses? a blown fuse could cause this problem.
I hate to say this but the repair was not complete. If the sound levels are different with the balance in the middle, then either they missed a problem in one of the pre-amp stages, or they used an incorrect substitution for transistors in one or more stages. This unit should be brought back to complete the repair.
Any additional detail would require that I see the actual unit and poke around inside with test equipment.
I have had the front, left and right channels go out over time.I have fixed all of them, and each time it has turned out to be a cold solder joint.While I love NAD and will continue to purchase there equipment, this generation is plagued with poor workmanship.
To fix the channel going out, I removed the top cover.Back cover and 2nd card from the left (looking at the receiver from the back side).This card handles all of the audio processing.I have found cold solder joints all over this board which has caused channels to suddenly go quite.I have never found a bad component.Also, I have cleaned the interconnect to be backplane (board that the audio processing board connects to) in the case of the center channel going quite.
If you have poor FM reception, the first board from the left (looking at the receiver from the back side) may have a cold solder joint on the coaxial connection for the FM antenna.
The blue screen indicates a proper connection (signal received by the monitor). Try selecting "amp" on your HTR 2 remote then use any directional button at the center of the remote, the keys which circle the "Enter" button. Hopefully you will then see the menu appear. Use the same directional keys to navigate the menus.
has bad 12 volt regultor and 2 5.1 volt zener diodes on the main board in the regulator circuit, also may have a few caps near these parts which also need replacing. ref # for the 12 volt reg is u703 , kinda a major job.
I have the same problem which started about a month ago and seems to be getting worse.
I also noticed today, that 1 channel is significantly louder than the other - fault in the pre-amp stage, as feeding the power stage directly gives balanced, albeit extremely loud sound!
Looking on eBay, I found someone else selling an amp with both problems. It would nice to think that NAD would acknowledge a design flaw, and fix for free, but my amp is 5 year old.
make sure the trigger switch in the back did not get switched to trigger, if thats o.k. it may have 2 regulators 2 5.1 zener diode and a capacitor or 2 deffective on the board in the regulator circuit. I have yet to see any bad outputs in a Nad T752, but I have only worked on three so far. Larry James
I have hard copies of both manuals, but there are ** specs in the 272 manual!
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