Technical information

TESTING SECTION: PART 1
WARNING!!! WARNING!!! WARNING!!! WARNING!!! WARNING!!! WARNING!!!
IT CAN NOT BE STRESSED ENOUGH THAT TUBE AMPLIFERS CARRY HIGH VOLTAGES, HIGH
ENOUGH TO CAUSE FATAL INJURY UNDER THE RIGHT CIRCUMSTANCES, EVEN AFTER AN AMP
HAS BEEN OFF FOR SEVERAL HOURS. IT IS ABSOLUTELY IMPARITIVE THAT YOU FOLLOW THE
SAFETY GUIDELINES DESCRIBED IN THE TESTING SECTION.
METROAMP ASSUMES NO RESPONSIBILTY OR LIABILITY FOR PERSONAL INJURY OR DEATH
CAUSED BY IMPROPER HANDLING, NEGLIGENCE OR MIS-USE OF OUR PRODUCTS.
IF YOU HAVE RESERVATIONS ABOUT THE TESTING AND POWERING ON OF YOUR NEWLY
ASSEMBLED AMP, WE SUGGEST THAT YOU CONSULT A QUALIFIED TECH TO HELP.
WARNING!!! WARNING!!! WARNING!!! WARNING!!! WARNING!!! WARNING!!!
To help identify points in the testing procedure that involve high voltages, we will indicate them in BOLD RED print.
We also suggest that you probe with your meter inside the amp using only one hand, put the other in your pocket. This
will help prevent you from inadvertently touching two points that might complete a circuit. If you make safety a habit,
it could save you from a bad experience with your amp.
TECH NOTE: the six filter cap cans mounted on the chassis are electrolytic capacitors, which store electricity. They
can remain charged for hours or days after the amp is unplugged. You can NEVER assume there is no stored charge in
this amp! You MUST use the discharge method described here each and every time the amp has been powered on.
You should also verify with your meter every time that the stored electricity has been fully drained.
We suggest placing the amp upside-down in a clean work area, with the knobs facing you. You’ll need a suitable load
plugged into the output jack for testing once the output tubes are installed. A speaker cabinet rated for minimum 100
watts will work for this, as will a dummy load rated for 100 watts minimum at 8Ω or 16Ω.
Tools required for the testing section:
• Multi-meter capable of testing 500V AC/DC and 100mV DC
• 100 watt rated speaker cabinet or dummy load
• Small standard screwdriver for bias pot adjustment
• Alligator clip lead
All of the measurements taken in the testing section will be in
reference to ground. The chassis is the perfect ground point.
You can use a cage nut as a convenient point for your meter
negative lead.
This also allows you to probe using only the positive lead and one
hand.