A few tips for construction safety

A few tips for construction safety :

use bleeder resistors on your power supply caps ,
measure to be sure if the voltage is low enough

ground the chassis to the power supply ground and eventually earth the whole thing (watch out for earth loops use a earth lift switch if necessary)

when measuring , keep your left hand in your pocket (GOLDEN RULE )
use clips on meters so you don't need to hold the ground connection

allways check if the power plug is out when you put your
2 hands inside and voltages are discharged

use fuses with accurate ratings

How to power up a finished project for the first time :

1 remove tubes , power up and measure DC voltages and AC voltages
2 if so far no smoke is coming out ,add only rectifier tube and measure DC no load voltages
at this point , no fuse should blow and you check on the tube sockets for correct filament voltage and correct negative bias and high voltage ( Ucc or B+)
3 power off and add pre amp tubes
4 measure anode and cathode voltages , check if operating points are ok especially with direct coupled stages , check if current is within specs
5 power off , insert power tubes , connect to speaker
6 power briefly on , make sure feedback is feedback ( if used ) and not feed forward ( motorboating sound that gets louder ) if that's is the case reverse polarity of feedback
7 power back on , check quiescent current of outputtubes
8 if all is ok , measure all voltages anode and cathode of each stage and keep for reference

How to solve Problems : ( assuming no schematic at hand )

Tube equipment is very simple and straightforward :To function a tube needs filament supply , and power Visually you can see if the tubes have filament supply .
Then you measure high voltage and check with manual if this is possible for the tubes used
Example : EL84 runs at 250 volts average if you measure 400 volts or only 150 volts something is probably wrong . Then you check each stage : anode voltage , cathode voltage ( know you're tube pinning ) .Simple rule , a tube needs current , so example ECC83 runs usually at 1mA ( 0,5mA to 2,0mA ) .If there is no voltage drop across a resistor something is wrong ,change the tube , change the resistor .Without power you can measure resitors with an ohmmeter , no need to disconnect ( tube imp is quite high )
Also measure leakage of power supply capacitors , this can be done by charging the capacitor and disconnecting it , so its unloaded , if the voltage drops fast its for the garbage
Example after 5 minutes less the 80% of charged voltages
Signal capacitors , should not let DC through ( measure infinite with ohmmeter ) if you have a signal generator you can trace the signal , otherwise use a capacitor meter and measure if you have a doubt . Chokes have a dc resistance that should be reasonable .
Example small chokes for pre amps can have up to 1000 ohms DC resistance
Power supply chokes however should not exceed 350 ohms and preferably be lower
Output transformer test : measure static DC resitance (primary average 150 ohms secondary less then 2 ohms THIS is on average )
If not sure : connect a 6Volt AC source to secondary and measure primary voltage ,
Should be much higher , this gives you the step up ratio
Check if impedance matches the outputtubes
Ratio (squared ) x impedance speaker = load tube sees

I guess I can send you all my repairables now !!!!!!!!

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