I've just finished building my ST-70 with the VTA board (low gain version).
I build the amp from scratch using an unbuilt kit from the early sixties and the VTA board. I tested the output transformers beforehand but not the power transformer. So, I have no idea on how the components will react; they are new but 50 years old!
I intend to proceed step by step in turning this amp on to avoid any catastrophic failure. These are the steps:
.- pulling out all tubes, connect resistance loads, check the AC voltages at the different secondaries of the power transformer: the B+ one, the filament ones;
.- if the power transformer is working fine, then I will insert the rectifier tube and check the DC voltages and inspect their forms on a scope;
.- only then, if the values seem on range, I would insert one set of output tubes and check and adjust roughly the bias; I will do the same for the other channel;
.- I will next insert the 3 driver tubes and, after appropriate warmup time fine-tune the bias;
.- I will proceed to the AC balance test;
.- I will again check voltages and finally I will inject a 1000 Hz signal and check for clipping on a scope.
Have I forgotten something here or am I doing a useless or much worse a harmful procedure ?
I would appreciate your feedback