Nad 705 repair

[Eastham]

Was checking the schematic. Where you picked up ground looked ok. Pull the regulator and check the cap C319 to ground.

63mV on the cap. Solder pads for IC303 measure 14.91v in 0 ground amd 75mV out. My guess is IC303 is toast.

 

[lokerola]

Here's a few tips; don't spend to long on a single solder pad, if you do you'll porbably end up lifting the trace from the board, use flux, lead based solder and solder wick. and if possible get a temprature controlled soldering iron. when replacing cap values never go down in voltage or change the capacitance to much.

Thanks!

 

[Eastham]

Thanks!

No problem!

 

[Eastham]

I just fired the LM7812 with a old 12v wall wart. Measuring from the ground pin to the negative wire of the wall wart I got the output voltage which was 11.67v so yeah, I think it's gonezo.

 

[NAD80]

Replace it and go from hopefully that will fix it.

 

[Eastham]

Replace it and go from hopefully that will fix it.

With any luck! Found a bunch of bad joints on the tuner board on the little TO92 trannies, IC's and connectors. I also found a broken trace on X401 so I repaird it with a bodge wire and touched up the other solder joint. Theres also a lot of joints that look like they've been reflowed, probably the person who wrapped the wires together with electricians tape. Now with zip ties.

 

[NAD80]

Reflow all of it. Check every board and the wiring just in case.

 

[Eastham]

Reflow all of it. Check every board and the wiring just in case.

Will do. I guess I under estimated how bad NAD solder joints are.

 

[NAD80]

Not just Nad had problems with the soldering after all these years. And depending where it was built could affect the longevity of the solder joint. But when Nad sounds good it's good.

 

[Eastham]

Not just Nad had problems with the soldering after all these years. And depending where it was built could affect the longevity of the solder joint. But when Nad sounds good it's good.

I believe the Yamaha CR **20 series receivers had solder issues on the bigger components. I can attest to the sound for sure! For those brief 5 minutes a NAD is working it's amazing! In all seriousness this NAD has really grown on me, I wonder what it is that makes some amplifiers sound better than others, that thing that makes drums, cymbals and other things the upper mid - treble ranges sound so defined and clear, and the spacious seperation. I can tell why NADs have such a following. It's by far the best amplification device I've owned yet.

 

[NAD80]

Nad did really great on the design in the beginning. It's just when the bean counters struck it did not help. Check out the Nad 3020 threads with leesonic's work on the restoration of the amps. Had my 3140 since it was new. No problem with it. The 3020 stunned the audio critics when it came out that a budget amp could sound that good.

 

[Eastham]

Nad did really great on the design in the beginning. It's just when the bean counters struck it did not help. Check out the Nad 3020 threads with leesonic's work on the restoration of the amps. Had my 3140 since it was new. No problem with it. The 3020 stunned the audio critics when it came out that a budget amp could sound that good.

I was originally looking for a 3020 when I was looking at all the NADs on eBay but everyone wanted more than I could afford, then I saw this for spares or repair and though I'd chance it an threw in a bid, £37.07 later here we are. The 3020's are cool and if I come across one cheap enough I'll be snapping it up to see how it compares to my 705. Plus like you say the 3020 is iconic, when you hear NAD you think of the 3020.

 

[Eastham]

Thanks!

Some more advice for you, always power the unit up after re-capping each board to make sure you haven't made any mistakes. This will isolate any problem to the board you just completed. Build a dim bulb tester too, power your device up with it until you have completed the re-cap and checked all voltages. This will save the amp from being damaged if you accidentally short anything or install anything wrong.

 

[lokerola]

Some more advice for you, always power the unit up after re-capping each board to make sure you haven't made any mistakes. This will isolate any problem to the board you just completed. Build a dim bulb tester too, power your device up with it until you have completed the re-cap and checked all voltages. This will save the amp from being damaged if you accidentally short anything or install anything wrong.

Do most people use the ESR meter to test capacitors while they are one the circuit board, or do most people de-solder each cap, test with a multimeter, then re-install or replace as-needed? Thanks much.

 

[Eastham]

Do most people use the ESR meter to test capacitors while they are one the circuit board, or do most people de-solder each cap, test with a multimeter, then re-install or replace as-needed? Thanks much.

A re-cap usually involves replacing every cap in the unit, regardless of weather it measures good. You can test if a cap is bad in circuit but I'd recommend you remove them for exact readings.

 

[slimecity]

Elechickens tape all over the place

You gotta clean this stuff up otherwise its eggs and feathers all over the place.

 

[Eastham]

You gotta clean this stuff up otherwise its eggs and feathers all over the place.

Tell me about it, and if the eggs hatch dear god!

 

[lokerola]

A re-cap usually involves replacing every cap in the unit, regardless of weather it measures good. You can test if a cap is bad in circuit but I'd recommend you remove them for exact readings.

Got it - thanks.

 

[NAD80]

Eastham did you get any further with the 705?

 

[Eastham]

Eastham did you get any further with the 705?

Just waiting on the parts, should be here tomorrow.