• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

NAD 1600 Monitor Series Tuner/Preamp... sonic upgrades?

Well... After changing op amps and some caps, it's not working properly.
Seems some missing supply voltages around.. But pwr supply is delivering.
Hm...
 
Good work with the sockets. For i can see on your pics, you are using the original opamps. What opamp do you plan to install, considering that the unit rails are 18.5V, that is above the limit of many popular audio opamps ?
 
MWH901 said:
Evening all,

I recently picked up one of these off the 'Bay in a "will not power up" state. One new relay and a few reflowed solder joints later, she's alive and kicking!

Unlike many NADs I've worked on, the cheapo caps all test surprisingly good, and as such I do not intend to recap the unit. That said, I would greatly appreciate if anyone has worked on one of these and can recommend a few select caps or other components to upgrade to improve sound quality. Also, any common modes of failure where a pre-emptive part swap would help ensure longevity.

Thanks in advance...
-Mike
Click to expand...

If you ever need to clean the volume pot on your 1600... spray Deoxit Fader spray into the notched stamped steel piece (next to the yellow "V"). And work the dial a few times. Worked for me.

Click onto image to enlarge. :)

NAD_1600_volume_pot.jpg
 
I replaced the power supply caps for some nichicon 2200uf, twice the value at 50V also. They fit perfectly within the existing holes on the board. The old ones looked damaged. After removing them and measure them, the capacitance was right on the spot, about 1000uf .
1692028824945.png

All the pots and switches are perfect, feel good with no noise. All the controls from the board work. An imbalance between the channels has disappeared now and the unit is very clean sounding, you have to raise the volume to the above the maximum input level of the amp to hear crosstalk. Most of the buttons on the remote control trigger actions on the unit, but the motorized pot is not responsive.
1692029378099.png


These are the steps taken to refurbish the unit.
Power supply caps changed and upgraded to Nichicon 2200 uf, the only components that were visually bad, board vacuumed and cleaned to remove nicotine and dust with brushes and alcohol/ board cleaner, conductive oxidized RTB removed and cleaned, new RTB applied to all ribbons, all pots cleaned with contact cleaner and deoxit, all removable sides of the unit , front panel and knobs / pushbuttons removed washed with soap and alcohol.
 
Last edited:
Mr Boochie said:
Maybe the control board for that pot motor needs soldering?
Click to expand...
I will enjoy for a week or two, just installed it two days ago and will try to reflow and clean the motorized pot. It sound really nice, including the turntable interface.

Another thing that does not make sense is the remote. It was disassembled and and cleaned, and all key presses turn the LED on on the remote.

When I press the keys, certain functions ( video, fm, turntable) would not work consistently, i.e. re receiver remote acknowledge led does not turn while the remote led is flashing. It is inconsistent. Any idea>

tks.
-
 
Last edited:
Today I took the NAD 1600 out of rotation to test an akai ps200c.

The remote after all was ok, I was able to use it to program an universal. Seems that the preamp does not respond to the commands. Since the unit is off, I will retouch the solder joints of the volume pot and place some deoxit on it and see what happens
 
The motor is working now. The power pin of the motor needed to be retouched with solder. I will also, now that is open retouch the pins of the h bridge motor controller.

Also, in the tuner amp there is a 7815 and a 7805, the input caps have a lot of the brown glue cup ana one of them has some burn marks. May need to replace or test.
 
I have seen another possible upgrade, that might be an oversight on the design. The main diode bridge is fed by a 65 V transformer at idle in the preamp, measured at the inputs of the rectifier bridge is about 65V rms. Counting that the line voltage can can go up over up to 125V, the output voltage of the transformer would exceed the rating of the regulator, the W01M , that is 70V. This is the main bridge that feeds the +- 18.5V and the +- 24V and +- 18V regulators (six in total) for the audio portion (relays, motor pot and logic have other regulators and transformer). In the manual I could not find any info about the transformers.

For what I see, in this family of bridges, it should be upgraded at least to the W02M (100V). I've already upgraded damaged C504/5 to 2200uF Nichicons .

Is there any part that can fit the form factor that has less noise than my proposed replacement (W02M)?

1710515402746.png

1710515343468.png

https://www.tme.com/Document/d166dcaa4ce7eb996e9638af4086de0a/W10M_ser.pdf
1710514316122.png
 
Last edited:
On the tuner board there are a 78M05 and a 78M15 that are always on even when the unit is on standby. The input caps, very close to the heatsinks were all burned outside. C553, 15V (22V transformer) and C573 for the 5V (11V transformer) . I replaced them with Nichicon 2200 uF 50V UPW same as they were used before in the main power supply ( see post 27), since I have them around and I belive the new value will work fine. Also, all the functions of the remote control work now (not claiming that is related).

The RTV silicone on the wire wrap connector has been added as a pressure relief for the cables, as they get stretched every time the preamp get serviced.

1714447772859.png
1714447842532.png
1714449455727.png




nad1600_78m05_sch.pngnad1600_78m05_brd.png numbers were
 
Does anyone know the specs on the T501 transformer in the 1600? It's the one that connects to the tuner board. It's a TAM Model 24D043HD, I think and is the same one used in the 7000 model. I'm looking for a functional replacement.

Or alternatively, does anyone know how to replace the thermal fuse in it? I'm assuming that I blew the thermal fuse since it's not working and I did accidentally short something out, but don't remember what it was anymore. I've opened up the transformer, but can't find a thermal fuse, so I assume that it's deep inside.

Thanks for any help.
 
You must log in or register to reply here.
Back
Top Bottom