If interested I have some XPL909 for sale


** They the ones with inbuilt B-E resistor or is that the XPL910 ?

A DMM will show about 68 ohms B-E with either polarity at the probes.

BTW:

Phase 400s had in *interesting* design flaw that would cause both channels
to go DC when one channel suffered an output device failure, due to using
common DC fusing for both channels. It worked like this:

1. A single output device fails short in channel A sending that output full
rail DC.

2. The same channel tries to pull the output back to zero by driving the 3
output devices on the other side hard - so one or more of them fails short
immediately due to SOA being grossly exceeded.

3. Channel A's output stage is now shorted rail to rail.

3. One of the two DC rail fuses instantly opens removing the short on the
PSU.

4. Both channels now have their DC supplies connected to a single rail of
either + or - 85V.

5. One of the "flyback" diodes wired from DC rail to speaker output become
forward biased in channel B.

6. The speakers connected to both channels now start smoking .....

FYI:

One can normally remove either DC rail fuse on a PL400 with no ill effect.

The PL700 has 4 DC rail fuses, which eliminates the problem.

Many stereo power amps have NO rail fuses, which also eliminates the
problem by forcing the AC supply fuse to blow.


..... Phil