*See engineers notes at rear
Page 3
MB805
Layout and Features
If you are inserting the MB 805 valve for the first time, it may be helpful to observe the slot
in the valve base to indicate the degree of rotation needed to fit the valve correctly.
Page 1: ...ve 805 has to do all the work of both the up and down parts of the waveform In order to go down the valve must be running at 100 of its maximum power unlike push pull amplifiers where the idle current...
Page 2: ...mplifier finish Internal wiring check Check Triode mode N A Run min 6 hour test Check input Output Valve Bias level v Sound Quality Channel Balance Valve Microphony Valve Seating Hum level L R mv RF T...
Page 3: ...t rear Page 3 MB805 Layout and Features If you are inserting the MB 805 valve for the first time it may be helpful to observe the slot in the valve base to indicate the degree of rotation needed to fi...
Page 4: ...tral terminal and Green Yellow to Earth terminal 6 SWITCH ON The blue mains indicator should light up The 805s will glow bright yellow You will likely hear a humming noise for a few seconds this is no...
Page 5: ...and play some music with plenty of bass e g dance music preferably in mono FM tuners are usually switchable to mono and stand the speakers close together If correct you should hear plenty of bass if...
Page 6: ...valve This could be due a faulty 805 or one of the 805 internal fuses blowing A symptom of this would be no bias voltage at the test point Also the valve would not be as hot as normal Refer to an engi...
Page 7: ...s ground by unscrewing the 0 speaker terminal and tightening the probe in the exposed hole And the red probe in the test socket adjacent to the valve on test Set the Icon meter to 2000mv or the black...
Page 8: ...the mains plug at least 20 minutes beforehand This will enable dangerous voltages to dissipate and the valves to cool down If possible check the bias setting before you attempt to change the valve s i...
Page 9: ...e It is not guaranteed for commercial Public Address use or use in other situations The guarantee becomes void if the unit has been modified in any way not approved by Icon Audio Please contact us 10...
Page 10: ...or variable transformer will be useful to operate the amplifier on reduced power in order the trace the fault or overload Make sure the bias for the 805s is correct If the AC fuse is blowing with the...
