I have an Australian "copy" of a Fender Showman Ab763..made in the 1970's by Eminar. The amp came to me after a local music shop had it overhauled and then sold it to a customer who returned it complaining that it was making horrible noises. After checking it out I agreed...horrible noises from bad and mismatched power tubes , dodgy caps between the PI and power tubes and dirty preamp sockets. I replaced all those and that solved the noise issue. But... the normal (non tremolo ) channel was insanely loud compared to the tremolo channel so I assumed there was a fault with the tremolo channel and checked every component and voltage in that channel only to be left scratching my head as everything checked out ok. I told the shop what I had found and they offered to sell me the amp for a song as they didn't want to pay for all the work that had been done (and was still to come) . So now I had yet another tube amp to add to the other 11 that I own...what to do with it ...ah ha ...I need a bass amp...so I will change the tone stack in the normal channel to make it more suitable for a bass guitar. This channel only has volume, bass and treble controls and I use the tone stack calculator to figure out the right values of the caps and mid resistor and attack the tone stack. Well ...start to attack the tone stack until I realize that it is wired in strange ( to me ) manner. The mid resistor is not there at all which means the tone stack has no path to ground and the bass pot is wired differently...see the pics. I put in a 6.8k mid resistor and rewired the bass pot in the usual fender way and bingo...the insanely loud channel is tamed and both channels now have the same volume. Changed 2 caps in the tone stack and it is better for bass. Some one had removed the mid resistor for some reason and rewired the bass pot and the last tech had not picked up on that ( unless he did it himself ??). If I had not wanted to alter the tone stack in that channel I would probably still be wondering what was wrong with the other channel. Never assume the previous tech did a good job...my assumption cost me about 4 hours time...but at least I have another tube amp at a bargain price...are 12 amps enough ?...probably not . Are assumptions ok...definitely not.