WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
And it's worth some good money if you have one or a pair of them. Unless you are going to build a transformer coupled line stage you might consider selling it/them on eBay and applying the funds to something more suitable.