Nad 5425, cd player

I started to messin' around with this nad unit - it doesn't play - that a bought cheap a few weeks ago.
Here's my first impressions:

From the outside:

This a well build machine from 92. Great and solid chassis with only a few little scratches. Awesome retro looks and all the knobs have a nice and smooth touch.



From the inside:

No signs of smoke. Actual fiberglass circuit board, not cheapo phenolic. a 60Hz analog PS. copper and iron transformer 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. A MASH dac 18 bit-resolution. Sony cd mechanism KSL-150 and almost every resistances are carbon film and lots of Elna caps. No ribbons to the display, it is mounted 90 degrees to the main board with a light hood/dust cover.

The laser is busted. Could be worst...

If i can repair it it will be a good cdp.







Must find another laser and then took it to a friend of mine who has an oscilloscope and a frequency counter to do the alignment and focus/tracking adgustments.

This post has been edited by clint e. on March 15, 2008 03:05 pm

I'd ordered today the cd lens KSS-210. A Sony made in Japan.

Still waiting for the Sony laser pickup.
Meanwhile, i'd changed all the Elite caps - about 18 - with Elna's and Nichicon gold. Now all the lytic caps are Elna and Nichicons.
I also put some new Jamicon's in parallel in the PS. It had 4400uF now it has 6000uF in parallel.
I also boost a few ones from 100uF to 220uF in the ins and outs of the opamps, and add 22uF of Nichicon gold in parallel to the outputs.









This post has been edited by clint e. on March 20, 2008 06:10 pm

that baby is going to sound good!

Yeah Scott, i got that feeling to.
I ordered the japan made Sony lens KSS 210 witch are one of the most reliable laser units ever on the market. A thousand times more reliable than the crappy CDM12 series Philips garbage that too many people get stuck with, even by supposedly "high end" companies.

So, it has it all to be a very good "vintage cdp". Good chassis, Good transformer, good pcb, good caps and resistors and i also made a new wire ground from the pcb to the chassis.

Here's some spechs:

From the Nad 5425 cdp:



And from one of the lastest Nad cdp, the C521:



Not bad at all compared to C521....

nice work. I have owned several NAD CDP's over the years. I currently am using a NAD 5340 as my 2 ch player hooked up to a California Audio Labs Alpha tube DAC with Electro Harmonix 12AX7 tubes.

sounds pretty decent.. but the CD player is somewhat dated.. and does reveal it's limitations on music, even running just as a transport.

This post has been edited by Danger Boy on March 23, 2008 09:02 pm

Sometimes i wonder if a 16/44 (MASH/Bitstream PWM systems) cdp is really dated....?!

IMO i came to a shocking conclusion. I mean, it all depends after all from what we expect from the music you listen...
I still find 16/44 bitrate very pleasent compared to all the oversaplimg from nowadays, mostly because the sound of a CD player is more than just the number of bits. It's the quality of the converter, the filter requirements imposed by that converter, the quality of the filter, and of course, the quality of the following analog components.

About the Nad 5425, i was thinking also to change the old opamps - NE5532 - to a more modern ones like OPA627. Then i ask mysel if i really want a clean with no balls and a plastic-sounding top end..?! that is the sound of a lot of clean opamps... or a more warm, and a more musical "sound" like the old ones...?
I choose the old ones.

IMHO, bitrate above 16/44 doesn't mean nothing to me.

The Sony laser pickup just arrived.





This week i'll put this baby in shape.

how difficult is it to align the laser?

I haven't done that yet. But, with the help of a friend who have the right tools - an oscilloscope and a frequency analyzer - and also with the service manual adjustment points, i think it will work out fine.
I hope...

Here's for example, some symptoms of a bad focus and tracking:



BTW, tanx for the input.

why do you like a fiberglass board over a phenolic? we use alot of phenolic on aircraft because of its strength and light weight. Is there something I don't know?

I'm sorry I miss spoke it isn't light weight but it is tough.

Because it has rapid heat dissipation, fiberglass has excellent heat resistance in case you need to solder and desoldering various components, also is highly resistant to attack by most chemicals, fungus or bacteria.
And along with its high dielectric strength and low dielectric constant, imo glass is of major importance and usefulness in the electronics.

Of course you could say phenolic has almost the same properties, but i prefer the good old fiberglass.

but isn't glass more brittle.i agree on the heat aspect.

Victory!
The Nad is playing for almost 2 hours now. Later i'll make a small review, for now a few pics: