NAD 5425 cd player mods?

[john8417]

I have my NAD 5425 cd player apart to replace the display lights again. While I have it open I would like to improve the sound a bit. I have deadened the chassis with Dynamat and the ICs with lead tape, all with great results. I think that the high freqs are the worst part of the sound, so I'm thinking of replacing the ouput coupling caps with something better. Does anyone know which ones they are? Should I remove the muting transisters? Should I remove the power supply decoupler resisters? A schematic would of course help. Thanks

[howard228]

Just wondering if you'd found the schematics. I could email it if you need it.
BTW, what's your thoughts about modifying the NAD5425? Have you done any to it yet?

Howard

[rcavictim]

I just found a NAD 5425 CD player at the landfill site last week and grabbed it because it looked to be in good shape and is a heavy piece of gear, indicating that it is probably made out of real materials and has some quality to it unlike the BPC that one usually sees. I'll bet it has a real power supply with an iron, 60 Hz xfmer instead of a flaky ultrasonic switchmode miracle looking for any excuse to fuse.

I haven't had a chance to test it yet.

Is this a worthwhile player to fix/upgrade? Are the original DAC's up to audiophile expectations?

[rcavictim]

I finally got a chance to look at the NAD player last night which I saved from the local landfill site. The power light and display are dark, no clues that the unit is powered up BUT..... it works!

It appears to operate perfectly and sounds fine as far as I could tell on one CD which happened to be in the tray as found.

Man, there's nothing like having a good dump.

Anatech or anyone else have any knowledge of what usually goes wrong with this consumer stuff when a display goes dead? Do these things get a dedicated supply rail for the LED's?

[mlloyd1]

I had a dead display in my otherwise fully-functioning family room CD changer (a cheap Sony - don't remember the model). Turns out the flaky ribbon cable that connects the display panel to the main board had slid out of it's socket. Plugged it back in and glued it down in a couple of places so as not to get bumped by the disc loading mechanism anymore and it works like a champ. Hopefully, you'll be so lucky, too!

mlloyd1

Originally posted by rcavictim
I finally got a chance to look at the NAD player last night which I saved from the local landfill site. The power light and display are dark, no clues that the unit is powered up BUT..... it works!

It appears to operate perfectly and sounds fine as far as I could tell on one CD which happened to be in the tray as found.

Man, there's nothing like having a good dump.

Anatech or anyone else have any knowledge of what usually goes wrong with this consumer stuff when a display goes dead? Do these things get a dedicated supply rail for the LED's?

[rcavictim]

Originally posted by mlloyd1
I had a dead display in my otherwise fully-functioning family room CD changer (a cheap Sony - don't remember the model). Turns out the flaky ribbon cable that connects the display panel to the main board had slid out of it's socket. Plugged it back in and glued it down in a couple of places so as not to get bumped by the disc loading mechanism anymore and it works like a champ. Hopefully, you'll be so lucky, too!

mlloyd1

Thanx m. Guess I'll have to yank the cover.

[rcavictim]

Cover yanked. Spotless inside. No signs of smoke. Actual fiberglass circuit board, not cheapo phenolic. As I predicted a 60Hz analog PS. copper and iron xfmer 18-0-18 VAC, two fuses to discrete 1N400? bridge followed by electrolytics and 3-term regulators. Good. I see some (4) Signetics NE5532 op amps (8 pin dips), two in each channel's audio path. No ribbons to the display, it is mounted 90 degrees to the main board with a light hood/dust cover.

Schematic time. The unit is circa 1992.

[rcavictim]

Originally posted by john8417
I have my NAD 5425 cd player apart to replace the display lights again....

OK, just happened to read the post again that started this thread. Duh! Ya' mean this baby uses light bulbs inside that display cover? That must be my problem too since as I discovered all else appears to work perfectly.

[anatech]

Hi Rob!,
Just saw the thread.

Let me have a look here ...... No manual - darn.

Also keep an eye out for solder joints on the regulators and a device called a semifuse. They look exacty like a transistor, but with only two legs. You will generally not be able to see the legs.

Find the oscillator and stick a scope probe on it. You should be able to see a scan waveform on the display pins.

If you get stuck, you are more than welcome to stop by Rob. Great find!

-Chris

[rcavictim]

Originally posted by anatech
Hi Rob!,
Just saw the thread.

Let me have a look here ...... No manual - darn.

Also keep an eye out for solder joints on the regulators and a device called a semifuse. They look exacty like a transistor, but with only two legs. You will generally not be able to see the legs.

Find the oscillator and stick a scope probe on it. You should be able to see a scan waveform on the display pins.

If you get stuck, you are more than welcome to stop by Rob. Great find!

-Chris

Thanx Chris,

I'm going to try to remove the display rear cover to find the alleged grain of wheat bulbs. I wonder if I could replace 'em with white LED's and series limiting R's?

If it is a scanned self illuminating display i'll try your advice.