Philips CD-i Mono III / IV Fuses

Philips CD-i Mono III / IV Fuses

Replacing blown fuses in Philips CD-i players with Mono III and Mono IV mainboards – sounds too simple to write an article about. That’s why I’m going to dig a bit deeper into the topic. An important fuse sits on the mainboard and protects the -5 V rail. I tripped (over) it by accident and was confronted with these weird symptoms that are hard to diagnose:

  • No video output (well, there is something, but see below)
  • Service Shell video output with a rolling/flickering image
  • The disc tray opens on its own (tray loader motor is constantly spinning)
  • The spindle motor is constantly spinning
  • “cd” flashing on the VFD

Apart from that, the CD-i player seemed to be working:

  • Low-Level Test doesn’t show any error
  • Remote control indicator lights up and movement is possible in the Service Shell (when you’re able to make out the image)

The accident

Some time ago, while doing measurements on the extension connector of the CDI470 that I use for experiments, I slipped with a probe and shorted the +5 and -5 V rails.

Philips CD-i Mono III / IV extension connector
Philips CD-i Mono III / IV extension connector

Immediately, the video signal was lost and didn’t come back after a power cycle. At first, I thought that my experiments with NVRAM upgrade and DFO were the root cause and that shorting the pins just gave the final blow to the mainboard. But it turned out to be something else.

After several power cycles and letting is rest for a while, I noticed that the motors were spinning. Now, spinning motors are usually a sign of problems with the power supply, especially the -5 V rail. When I checked the power supply, I was surprised that there weren’t any fuses at all, like the power supplies of the large players use to have. Also, all voltages were fine. I checked again at the extension connector (more carefully this time) and found that -5 V wasn’t there anymore.

The fuse

In the 470 service manual, the fuse 3255 MP100 is close to the connector for the power supply.

CDI470 and 490 power connector
CDI470 and 490 power connector

A quick look on the mainboard confirms that it is right next to the power supply connector (grid square F1). This applies to all Mono IV mainboards, by the way.

In the components list, there’s some more information:
Philips 12NC: 4822 252 51173 and 65V 1.0A. But MP100 already gave it away: It’s a Littelfuse 398 Series TE5 modul protector fuse.

I ordered a couple of replacement parts and replaced the broken fuse. Here are some pictures that I took of the old and new fuses:

With the new fuse, everything went back to normal and my 470 works perfectly fine with all its modifications. The article could end here, but we’re not quite done yet.

Mono III

On Mono III mainboards, the fuse has ID 3274 and sits farther away from the power connector in grid square F3.

Fuse in Mono III grid square F3
Fuse in Mono III grid square F3

Power supplies

Make sure to unplug the power lead before inspecting the power supply. Also, leave the power switch in “on” position for a while. I’ve marked the filter capacitors (2103) with a warning sign because they can zap you if you don’t discharge them!

If you need to measure something while it is switched on then make sure that it cannot move, keep away from the live area and don’t run it without load.


As mentioned before, I expected the power supply to have fuses for the individual rails. Just have a look at 20PS302 which is used in Mono III CD-i players (e.g., 210/40 and 220/60). Apart from the main fuse (1101“T1.0A L 250V”), there are plenty of fuses for the rails:

+5 V (1201 and 1203)
-5 V (1202)
+24 V (1204)

All of them are Littelfuse MP400 – 65 V 4 A (information in service manual component list: 4822 252 51179 PROT DEV 65V 4A).

Philips 20PS302
Philips 20PS302


470 and 490 (small Mono IV players) have power supplies that are split into two parts (20PS304). The small part with the main fuse (1101“T1.0A L 250V”) sits in the back of the player and the big part in the front. There are no additional fuses.

Philips 20PS304
Philips 20PS304


The 20PS306 power supply is used in large Mono IV consumer players, such as 220/80. It is the same as 20PS302 but has axial pico fuses (marking: “4000”) instead (thanks to Stovent for checking that out).
The information in the service manual component list is still the same (4822 252 51179 PROT DEV 65V 4A).


I’ve found another power supply (20PS307) in a 660/00 and it says “PSU CDI 615” on the silk screen. I assume that it is used in all large Mono IV professional players (615, 660, 670). Apart from the mains fuse (1101“T1.0A L 250V”), only the +5 V rail is protected (1200 and 1201; Littelfuse MP315 – 65 V 3,15 A).

Philips 20PS307
Philips 20PS307

Conclusion and tips for testing

Whatever power issue or other unknown symptom your CD-i player shows, always check the supply voltages in several locations:

  1. On both power connectors (mainboard and power supply) to rule out problems with the power supply, fuses (if available) and the connection cable.
  2. On the mainboard in the locations indicated in the service manuals.

While the service manuals are usually very clear about where to check +5 V supply voltage of individual chips, they don’t tell you where to check -5 V. Check the schematics and you’ll find that the latter is used by servo op-amps and audio/video amplifier circuits. The easiest way to access it, however, is the extension connector. To avoid future accidents, I crimped a 3-pin JST-PH (2 mm) plug to an old PC fan cable. You can use an adapter like that to safely connect probes to the extension connector (pins A1 – B1 – C1).

There are even more supply voltages for large players that the service manuals are even less clear about or constantly mix up:
+24/25 V and/or +12/11 V. Depending on the player, you’ll usually find them on the connector for the display panel (or combo panel if the player doesn’t have a VFD). +12 V is needed for players with SCART connector to generate the Switch signal.

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