Modification of the HDSP PCI card - Self Oscillation

In some rare cases, the combination Hammerfall DSP System Multiface and HDSP PCI card can suffer from self-oscillation. The problem is caused by a diode in the power supply section of the PCI card Rev. 1.3 or below. Later Revisions are working correct. This error can be identified easily:

• The error occurs only with the combination Multiface/PCI card, not with CardBus or Digiface.
• The high-frequent tone does not start before the I/O-box is loaded from the driver.
• The high-frequent tone will rise in level significantly when external devices are connected to the Multiface.
• The high-frequent tone vanishes as soon as an external power supply is used for the Multiface.

The problem is caused by a diode in the power supply section of the PCI card. When this component does not match the expected characteristics (voltage drop about 1 Volt instead of 700 mV), the voltage regulator feeding the Multiface will begin to oscillate. The problem can be fixed with simple means in two ways:

A second diode, type 1N4148, will be soldered in parallel to the existing diode VD1 (type LL4148).

The existing diode VD1 will be replaced through a 1N4001 (up to 4007).

Please note that this modification may only be done by qualified service personnel. Improper handling of the PCI card causes loss of warranty and there will be repair or exchange costs. The normal procedure in case of the described self-oscillation problem is to exchange the PCI card via your retailer and/or distributor against a new card.

RME continues the strategy of releasing all information to the customer. We are not giving this information here because we want you to modify the PCI card on your own, but because we are aware of the fact that exchanging the PCI card will need a certain time in some cases, whereas any competent technician can do the modification within less than 5 minutes.