Yamaha SPX90 restoration

This processor is one of the most famous one in guitar racks and old studios. It was introduced in 1985 and quickly became successful, it was relatively cheap, and has some very interesting effects algorithms. One of them is the famous ‘Pitch Change C’ algorithm, used by many legendary session guitarists in that era, including Michael Landau (at least, he used this on his milestone ‘Tales From The Bulge’ album.

Michael Landau’s guitar rack system at the time when he was recorded the “Tales From The Bulge” album.

So i wanted to hear this unit with my own ears and bought a broken one from a local auction site.
I was lucky, it was suffered from the usual capacitor problems. The caps are more than 30 years old now and they dried up, you have to change those old caps in many older gears too.
I decided to replace the caps found in the power supply section (you must use 105 Celsius grade and LOW-ESR caps), and every caps in the internal audio signal path (change to an audio-grade Nichicon MUSE caps). Apart from that, the only problem was the contact errors at the input / output level switches. You have to de-solder and disassembly the switches to properly clean the contacts.
Unfortunately, to access the backside switches, you have to disassemble and pull out the mainboard from the rack-frame.
Maybe the replace of Input pot is also necessary, but in my case, that was in good state.

Fixing broken Philips reed relays (CD104)

I’ve got a broken vintage Philips CD104 CD-player many years ago. After correcting the common problems (PCB failures etc..) and fixing the servo section, the player played discs, but there were no sound. The failure of reed relays founded in various audio paths is also a common problem in those day’s philips cd players. (early types which utilized the famous 14bit TDA1540 DAC)

There are two assembled reed relays devices. One is for muting audio on power-on to eliminate a loud click, the other is for de-emphasis switching. The problem is that the reed tubes don’t shorts even if magnetic field is exist. It can be easily fixed with changing the broken reed tubes. I used some russian-made tubes, which are a little bigger than the originals (as seen on pictures) but can be used too.
After fixing, the player is operating again perfectly (after 30 years 🙂 )

SONY CDP-337ESD some internal photos

This is a beauty player from 1987. This era was one of the best of SONY high quality players. Its sound is amazing (thanks to the precise engineering, transport and -of course- the TDA1541 DAC chip.

Restoration of NSM4202 NSM4002 displays founded in Philips CD Players

This post is about the restoration of good old Philips CD Player’s display. In the 80’s, Philips released some types of players which utilized the National Semiconductor’s low pin count LED display: the NSM… series type. In this device there is a 35 bit shift register, and a LED driver, so it was easy to interface to system controller with 2 or 3 wires.

Unfortunately this display device is hard to find nowadays, and after 20-30 years, broken easily. (first just some of the segments, later all of the segment go dark.)

My goal was to keep the original look and feel of my Philips CD371 CD Player’s display, so i decided to disassemble the NSM4202 device to wire each led segment individually, and drive with external circuity. I was thinking that it is easy to implement the original function with a small microcontroller, with time multiplexed LED driving, but the original device is not time multiplexed (not flickered), it has steady and static light. So i looked, and find an excellent device, which has the original functionality for about 5 euros. (ST and MICREL is  same)
This device is: Micrel’s MM5450.

…to be continued…

– UPDATE 2011 december 30 – I uploaded a small pdf to show some information about wiring and correct pinouts. You can download here:
NSM4202 or NSM4002 display clone