This series of machines had a reputation for CD drive problems – the original optical pickup sled (KSM-440AAM) was made of thermoplastic and placed close to the power supply, eventually leading to uneven wear that moved the laser into a position where it was no longer parallel with the CD surface. Also, the first models (DTL-H1000, DTL-H1001, DTL-H1002) had problems with printf function and developers had to use another function instead. Inconsistent numbering was also used for the Yaroze machines, which were based on SCPH-5000 and later 1001/1002 hardware, but numbered DTL-H3000, DTL-H3001, and DTL-H3002. B silicon and no S-Video port)-their technical equivalents were the Japanese SCPH-3000, so for consistency should have been SCPH-3001 and SCPH-3002. and European launch units had the same part number series (SCPH-100x) as the Japanese launch units, but had different hardware (Rev. This also led to a discrepancy where the U.S. This started very early on with the original Japanese launch units the SCPH-1000, released on 3 December 1994, was the only model that had an S-Video port, which was removed on the next release. From an external viewpoint, the most notable change was the gradual reduction in the number of external connectors from the back of the unit. The PlayStation went through a number of variants during its production run, each accompanied by a change in the part number. The SCPH-900x revision saw the removal of the Parallel I/O port while the RCA jacks were removed in the SCPH-550x revision. A comparison of the SCPH-1001 (bottom), SCPH-5501 (middle) and SCPH-9001 (top) models.