Let's Repair this buzzing 1959 Ampeg M12

This Ampeg M12 was unbearably noisy. Let’s look at how we test the main circuit suspects. We will also test the more common tubes with my MaxiMatcher 2 and the more obscure ones with my trusty old B&K 700.
We will revisit the definition of ESR and use this knowledge to test the likely longevity of the electrolytic capacitors to help us decide if they stay or hit the bin with an unceremonious “ping”. I am a stickler for retaining as much of the original componentry in a vintage amp as possible and sadly too much of this gem was devalued by previous work.
If you thought biasing a self-biasing amp was not possible then stay tuned to see the methodology.
As always, please DO NOT DO what I show you in these videos. One slip and you will suffer a severe case of death.

Video Index
00:00 Introduction
00:48 Overview of the Ampeg’s condition
03:30 Applying power … slowly through Variac and Stepdown transformer
05:43 Dating the Transformers
07:00 The Multi-Capacitor can
07:30 Testing the Tubes on the MaxiMatcher and the B&K 700
13:08 What is the Equivalent Series Resistance
14:20 To Replace or Not to Replace the old waxy capacitors…that is the question.
16:55 Why no switching earth on the input sockets?
20:30 The decision to replace the input socket
22:10 How to bias a “Self-Biasing” Cathode bias output stage.
33:20 Wrong fuse. Replace fuse holder.