TROUBLE SHOOTING
While it is highly unlikely that you run into all, if any, of these situations, the following are
some test procedures that you should run in the event that your RM200MkI/MkII appears to
misbehave (the vast majority of problems encountered are attributed to noisy tubes and
improper component placement or grounding):
DISTORTION
Output tube distortion usually results from one or more of the output tubes becoming gassy
(having grid leakage). A gassy tube will cause the BIAS to change from the time you turn-
on your RM200MkI/MkII through the first hours or so of operation. A gassy tube draws
extra current when it gets hot and will run even hotter as a consequence. You may feel the
extra thermal heat from the output tube by holding your hand beside the bad (gassy) tube.
NEVER TOUCH A TUBE’S GLASS ENEVLOPE WHILE THE AMPLIFIER IS
OPERATING OR IMMEDIATELY UPON TURN-OFF! SEVERE BURNS WILL
RESULT! Darken the room and look for a part of the gray PLATE area of the tube
GLOWING RED. A gassy tube will also blow fuses when the amplifier is driven hard for
long periods. It is necessary to replace the bad (gassy) tube out of your amplifier, or you
will cause slow damage to the other tube in that pair.
Through our research and published speaker test date, we have found speakers whose
impedance drops markedly below the values stated by the manufacturer. When played
hard for long periods of time, this drop in impedance below the stated value causes
overheating of output tubes and premature gassiness.
We highly recommend using the lowest impedance speaker tap that you can without
experiencing clipping at your listening level. Quite often, a speaker will play louder and
cleaner on the lower impedance speaker tap.
BLOWN FUSES
There are two different types of fuses used in your RM200MkI/MkII: 250mA Slow Blow,
High Interrupting (interrupt rating: 1500A@250VAC) ceramic output tube fuses; and a
5Amp Slow Blow power supply fuse (2.5Amp Slow Blow for 240V mains).
The 250mA Slow Blow, High Interrupting (interrupt rating: 1500A@250VAC) output tube
fuse is in series with that cathode of each output tube. One tube fuse will blow if you have a
lint short, a gassy tube, or a power surge. You may or may not see a flash in the tube at
fault when this occurs…If the fuse blows, then there will be a drop in power on that side,
but sound will still be present. We suggest replacing the 250mA Slow Blow, High
Interrupting tube fuse at least two times before giving up on that tube.
The easiest way to find out if the 250 mA tube fuse is blown is to check the bias. If the tube
fuse is blown, then there will be zero-mV or just a few mV reading. The tubes will still light
because the tube fuse is only for the high voltage and not the heaters.
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