How to quickly repair Fender Bassman guitar amp negative bias failure

Fender Bassman dead! I expected the worst (Power transformer) After a quick checkout, the problem ended up being a open negative bias diode. Easy cheap fix. Contacted the owner, have a few more items to address, but the Bassman is operating again! Please keep in mind, this is an initial inspection and revival of the amp, Not a full repair. That will be wrapped up later.
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