Question about Audio Players & Recorders

1 Answer

Receiver (tuner) signal fade-out ---heat related

Hello. I'm a tech with a tuner problem...I have a NAD 7140 receiver which, when powered up, loses the radio signal after just a few minutes. Next to the tuner module there are 3 transistors. I've traced the signal fade-out to there with a scope. However, I need a schematic or, preferably, the service manual to continue the hunt. Using a can of chiller comes to mind but that's risky due to condensation and other phenomenon that can occur--especially with a unit as old as this one is. (abt 25 years) I have to wait a while for the unit to cool back down so I can quickly start troubleshooting again before the loss repeats itself. Any ideas where I can obtain a service manual? Heh, I don't think an NAD service center is going to be gracious enough to sell me one of theirs (food out of their mouths and all that...). Any help will be greatly appreciated! Thanks in advance, ----Rick

Posted by on

  • Richard C Cohen
    Richard C Cohen Mar 24, 2008

    Thanks for the input...the serial is 102335....I was told by a tech long ago that any NAD stuff manufactured in Hong Kong was basically junk because of poor quality control. Mine was made in Japan and is supposed to be ok. Never had a problem until now. There are 3 transistors located near the tuner module (Q102, 103, 104) I checked with the scope...the waveform of a few volts just drains away in 2-3 minutes down to nothing...the bar graph on front display correspondingly gets less and less until no signal is detected.There is an op-amp? located near the transistors (IC101). And, there is a power IC (IC104), located relatively nearby to the module towards the front. I assume it handles the incoming power to the front display? (Just guessing) Hope this helps...btw...the transformer mounted on the left side of the chassis which powers the whole upper pcb shows a LOUSY square wave--Looks more sinusoidal than square with the voltage drop-offs along the ramps--in other words, instead of a clean, vertical rise and decay, which would be a good quality square, the rise and decay looks delayed, forming a more sinusoidal shape. Don't know if this would affect anything--the rest of the receiver works perfectly.---Rick

  • Richard C Cohen
    Richard C Cohen Mar 28, 2008

    Hello, I found the defective transistor in the tuner module by using a chiller and O-scope. It's a C481. I also shotgun-soldered the entire upper pcb because of the aged condition of the solder pads. I uncovered a few "sizzlers"(near-cold joints) in the process. The board looks almost brand new now. In the meantime, I'm going to check the major parts houses for the transistor or a suitable substitute. If you know any sources for parts (that don't ask an arm and leg) please let me know...Thanks for the help!

×

1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • Master
  • 4,234 Answers

The main problem with the 7140 is that there are at least 3 versions that I am aware of. The varient is based upon the serial number. Can you post that here. I will look up the info for you. I have access to some NAD stuff. Post the part designations as well (Qxx) and I'll at least get you the exact part numbers etc.
Dan

Posted on Mar 23, 2008

  • ABRsvcs Mar 25, 2008

    I don't have the variant for your serial number at the moment. I've place the request with the appropriate folks to get a copy. I should have it in a few days. Stay tuned...

    Dan

  • ABRsvcs Mar 28, 2008

    The C481 is a 2SC481. It is available at tritronicsinc.com in the US for $7.44



    Hope this helps,

    Dan

×

1 Suggested Answer

6ya6ya
  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

Hi,
a 6ya expert can help you resolve that issue over the phone in a minute or two.
best thing about this new service is that you are never placed on hold and get to talk to real repairmen in the US.
the service is completely free and covers almost anything you can think of (from cars to computers, handyman, and even drones).
click here to download the app (for users in the US for now) and get all the help you need.
goodluck!

Posted on Jan 02, 2017

Add Your Answer

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

I get static and distortion in Stereo mode.


if you are reffering to a radio fm receiver, the issue is the signal strength is too low.so the multiplex transmission cannot be correctly unscrambled.mono reduces the cross channel interference.
use a high gain 12 db or above external vhf antenna to solve this problem

Jul 29, 2014 | NAD 7140 Stereo Receiver With Phono Input

1 Answer

NAD 7140 input selector does not work


The selector chip is not working, either there is no B+ to the ic or the chip has malfunctioned or one of the surrounding components dead, for this type of problem a schematic will be needed to track the problem. try www.nad.com contact customer support and the technical department for additional help.

Jun 15, 2012 | NAD Audio Players & Recorders

1 Answer

Nad 7140 fm low frequency hum


This is probably a 60 cycle hum and the problem is more likely confined to the am/fm board, there is a bad ground due to poor solder joints, broken ground wire, an open capacitor, this may not be easy to find, but it is a start.

Apr 22, 2012 | NAD 7140 Stereo Receiver With Phono Input

1 Answer

Hello. I get no sound out of my AVR 7000 Receiver. No cables behind has been touched in the past. I'm trying TEST TONE, and everything seems normal in the display, but still no sound. I use Preout a NAD...


You don't say if all speakers are silent or just the ones to the unspecified NAD power amp. Do ANY speakers work regardless of which device powers them? Could the NAD be the problem?

Dec 25, 2010 | Harman Kardon AVR 7000

2 Answers

NAD 7140


Hi okapi6

Use a 3.5mm stereo jack to RCA connector lead.
370a7a3.jpg Connect this to the AUX input on the back of the 7140, and away you go. Get the lead as an accessory from just about any electronics hobby store.

Dec 07, 2008 | NAD 712

1 Answer

NAD 7140


The clicking is the sound of a bad relay. A relay is an electrical switch that opens and closes under the control of another electrical circuit. There is no user solution for this. You'll have to take it to an electronics repair shop (~$150) or dump the whole unit.

Nov 22, 2008 | NAD 712

1 Answer

Would like to know year of manufacture for Nad 7140 stereo receiver


Hi - You can download the manual by clicking the link underlined in blue below:

Nad 7140

a797009.jpg



Please take a moment to rate this solution & let us know if the information given was useful to you - Good Luck!

Informatica

Sep 09, 2008 | NAD Audio Players & Recorders

1 Answer

Tuner Omits No Sound - Onkyo TX-SR605 7.1 Channels Receiver


Make sure your receiver is hooked up to proper AM and FM antennae. Try switching to AM, scan stations. If you hear AM static and/or weak signals the problem could be antennas are not hooked up. FM has AFT which blocks out weak or noisey stations and you wont hear anything without ant.

May 06, 2008 | Onkyo TX-SR605 Receiver

3 Answers

NAD 7155 Receiver's tuner not working.


I Have a Captive Works which suddenly loose signal when a file is loaded.
I factory reset it and Quality and level returns but as soon as i reload a bin file i loose signal.

Can you help with a solution?
Harpic

Mar 08, 2008 | Audio Players & Recorders

1 Answer

NAD 7140


Amplifier is about shot, need to replace IC pack or transistors (whichever it has). Could, remotely, be the speaker lines are installed incorrectly?out of phase. + to +, - to - from amp to speakers. Some amps will protect themselves when this condition occurs till fixed.

Aug 01, 2007 | NAD 712

Not finding what you are looking for?
Audio Players & Recorders Logo

Related Topics:

267 people viewed this question

Ask a Question

Usually answered in minutes!

Top Audio Players & Recorders Experts

kakima

Level 3 Expert

102366 Answers

 Grubhead
Grubhead

Level 3 Expert

4872 Answers

The Knight
The Knight

Level 3 Expert

72670 Answers

Are you an Audio Player and Recorder Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...