R Series V1.0 p 28
2. Replace one tube. Turn the amp on again. If the fuse blows (or the tube glows cherry
red, indicating an internal short), you've found the bad tube. Turn off the amp
immediately. If the fuse doesn't blow, replace the second tube and turn the amp on
again. If the fuse blows, or if the tube glows cherry red, the tube is bad. Turn off the
amp.
3. When the tubes have cooled, remove them. Replace both tubes with new ones.
(Don't throw away the good tube from the old pair, though--save it as a spare!)
Power amp tube first aid - Suprema, Chubster 55, R55-112
Like preamp tubes, power amp tubes can go bad or wear out. Your Fifty Five Twelve
has two power amp tubes, and if one goes bad, they should both be replaced. This
assures optimum output and tone.
If a power tube shorts out, the HT Fuse will be blown. Remove power from the amp and
replace the fuse before doing the following:
1. Remove the power tubes. Remember the way the eight pins are arranged, and note
that the center hole on the socket has a keyway that matches the center post on the
tube.
2. Replace one tube. Turn the amp on again. If the fuse blows (or the tube glows cherry
red, indicating an internal short), you've found the bad tube. Turn off the amp
immediately. If the fuse doesn't blow, replace the second tube and turn the amp on
again.
3. When the tubes have cooled, remove them. Replace both tubes. (Don't throw away
the good tube from the old pair, though--save it as a spare!)
Power amp tube first aid - R100-212
Like preamp tubes, power amp tubes can go bad or wear out. Your Hundred Duo
Twelve has four power amp tubes, and if one goes bad, they should all be replaced.
This assures optimum output and tone.
If a power tube shorts out, the HT Fuse will be blown. Remove power from the amp and
replace the fuse before doing the following:
1. Remove the power tubes. Remember the way the eight pins are arranged, and note
that the center hole on the socket has a keyway that matches the center post on the
tube.
2. Replace one tube. Turn the amp on. If the fuse blows (or the tube glows cherry red,
indicating an internal short), you've found the bad tube. Turn off the amp immediately. If
the fuse doesn't blow, replace another tube and turn the amp on again. Repeat this
procedure until you've determined which tube is bad.
3. When the tubes have cooled, remove them. Replace all four tubes. (Don't throw away
the good tubes from the old set, though--save them as spares!)
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