You can also swap out drivers without rebiasing. The output tubes are the
ones where you have to adjust the bias. Try the Tung-Sols... they sound
best, followed by the Electro Harmonix (which sound a bit brighter -
depending on your speakers, you may actually prefer these).
I believe yours is a Rev 3 (look at the tag on the back). Have not heard of
a Rev 4, so I believe this is the latest revision. The SE-40 is tricky to
bias properly, and done right may take some time. The only time you should
have problems with tubes is if you install 6L6GC's in place of the 5881's.
Even though the 6L6 is supposed to be a replacement for the 5881, it can draw
up to twice as much current - which will be out of range for the bias
adjustment pots (you can change a resistor and fix this). If you run over
640mV, you're going to kill the tubes. If you're thinking about running
6L6's, buy Svetlana's from thetubestore.com, and tell them you want Perfect
Pair #16 (or tubes that bias within the range of a 5881). Make sure you tell
them they are for a SE-40, as they know what is required. The Svetlana 6L6's
are a beautiful upgrade, and you can really hear the difference.
Most failures are caused by people installing 6L6's (which bias too high) or
by incorrectly setting the bias - both of which put additional strain on the
I've heard of some rectifier failures, but this is an easy (and cheap) part
to replace, should it fail. Your biggest worry is a shorted tube, as they
are not fused. This will burn up a resistor, or a trace on the circuit
board. Very easy to jumper around (if a trace melts) but I always wondered
why they did not fuse the output tubes. Generally speaking, they're very
reliable if operated within the biasing parameters. Yours has less than 100
hours on it, so I'd say you have many years of enjoyment to look forward to.
Here's a cheater I wrote for setting the bias (assumes you're using the PC
plug, as the colors differ from the factory tool).
BIASING THE GOLDEN TUBE SE-40 AMPLIFIER
1) Set the amplifier on the work surface facing you
2) Remove the 2 screws from the left side
3) Stand the amp up on the left side (where you just removed screws)
4) Remove the 2 screws from the right side (now facing up)
5) Remove the 6 screws from the bottom cover
6) Remove the bottom cover
***WARNING*** VOLTAGES ARE PRESENT INSIDE THE AMPLIFIER CHASSIS THAT
CAN CAUSE DEATH ON CONTACT. IF YOU HAVE ANY DOUBTS REGARDING YOUR
ABILITY TO SERVICE ELECTRONIC EQUIPMENT, TAKE IT TO SOMEONE WHO DOES
THIS FOR A LIVING. ALWAYS MAKE ADJUSTMENTS WITH A PLASTIC SCREWDRIVER
OR ALIGNMENT TOOL DESIGNED FOR THIS PURPOSE.
7) Connect the power cord
8) Connect the bias adapter to the lower connector
9) Set your multimeter to DC volts
10) Connect the black meter lead to the red wire
11) Connect the red meter lead to the yellow wire
12) Turn on the amplifier
13) Wait 3 minutes
14) Adjust the rear pot for 630 mV (0.630) left increases, right decreases
15) Move the red meter lead to the black wire (next to the yellow wire)
16) Adjust the center pot for 630 mV
17) Move the red meter lead to the black wire (next to the red wire)
18) Adjust the front pot for 630 mV
19) Turn off the amplifier and allow it to cool
20) Connect the bias adapter to the upper connector
21) Repeat steps 10-19
It may be necessary to repeat this procedure several times before the bias
readings are all in spec. Do not exceed 640 mV. Do not set bias over 630 mV,
as input power fluctuations will cause the bias voltage to slightly increase.
Hope this helps,