TubeDepot JTM45+, Инструкция по сборке

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Step 9 – Touch the red meter lead to turret T41. Adjust the bias control until you reach the
most negative voltage. This should be around - 56V (+/- 5V).
Step 10 – Remove the AC power by disconnecting the AC power cord from the AC source.
Power Tubes, Installation and Testing
Step 1 – Install the two power tubes.
Step 2 – Connect a speaker(s) to one of the output jacks and set the impedance selector to
the correct speaker impedance.
Step 3 – Turn all volume and tone controls to minimum positions. The power and standby
switches should remain in the “on” position.
Step 4 – Plug the amplifier's AC power cord into the AC power source at the wall.
Step 5 – The panel indicator should illuminate. Monitor for any unusual smoke or smells or
blown fuse. If anything unusual occurs or if loud hum is heard from the speaker, disconnect
power immediately and review all connections. Let the amplifier warm for 2 minutes.
Step 6 – With your multimeter on the 2 volt range (we will be reading mV), connect the
meter's black lead to chassis ground as before and carefully touch the meter's red lead to the
wire connecting pins 1 and 8 together on one of the power tubes. The voltage here should be
around 4 – 5 mV … or less.
Step 7 – While still measuring this pin 8 /1 combination of one of the power tubes, adjust the
bias pot until you read about 30mV on the meter. The voltage will take some time to settle so
you will have to readjust several times before it is steady.
Step 8 – Move the red lead to the other pin 8/1 connection on the other power tube. This
should be about the same voltage, +/- 5 milliVolts.
Step 9 – Remove both multimeter leads from the amp and set meter to the side. Leave the
amp running. Monitor the amp for a few minutes to make sure nothing is out of the ordinary.
Signal Injection, Final Testing
Step 1 – With no signal source connected, turn all the tone controls fully clockwise.
Step 2 – Turn the master volume control fully clockwise and listen for a low level hiss from the
speaker. There may be a slight hum too, but any dramatic hum indicates wiring troubles.
Step 3 – Turn the high treble control up and down, the level of hiss should increase and
decrease with the control. Return the control to the minimum setting.
Step 4 – Turn the normal channel volume control up and down. The level of hiss should
increase and decrease with the control. There may be a slight hum as well, but any dramatic
hum indicates wiring troubles. Return the control to the minimum setting.
Step 5 – With a 1/4” guitar cord, connect a suitable signal source (a guitar if preferred) into
the number 1 jacks nearest the word “normal” (these are the “high treble” inputs).
Step 6 – Slowly turn up the “high treble” channel and listen to the sound source. Adjust the
volume to verify that the level goes up and down accordingly.
Step 7 – Repeat the same for the #2 input (s) and the “normal” channel control.
Step 8 – If everything checks good, turn off the amp.
A signal source can be a guitar or high impedance microphone or even a low level CD or
MP3 player. Using a speaker output from another amp is not recommended.
NOTE
8.4
8.5
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