'63 Fender Concert 6G12-A Part 1 : Initial Inspection, Playing, and Testing

Getting these harmonic tremolo circuits to behave themselves can be tricky. Lots of layers to this onion.
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[@Tonetwisters]

These are wonderful amps. The second and third amps I ever played through, were two of these, but darn near brand new. The first of these, gave me one horrific back ache from carrying it way too far from the parking lot into the venue back when I was maybe 16 years old and weighed 140 pounds.

[@NudnikShpilkus]

Nice. The later 6G12-A circuit with 6 preamp tubes. Played a '60 at a shop in Scottsdale. 5 tubes, B/T/V knob order. Should've bought it.

[@AROSFC]

IC caps are being selled as Vishay at Mouser....if you don't open the technical sheet you'll get IC caps at your home after buying them online....Mouser answer 'Vishay bought IC so they're the same.....'

[@goodun2974]

I rehabbed one of these a few years ago ---- after getting the tremolo working again, one of the other techs said, "why doesn't the tremolo on my Deluxe reissue sound like that?" 🤭

[@chokkan7]

I realize that your analysis of this amp is not yet complete, but I have a question: given the period this amp was built, I'm assuming that it uses an opto-isolator in the tremolo circuit, and I've seen those in amps that were 'thudding' (this is the worst example I've seen, though). There is another tremolo circuit I've come across in old Montgomery Ward amps where the oscillator current is fed into the cathode circuit of a gain stage, and I haven't heard those 'thud' (just haven't experienced it; not saying it's not possible); I actually like the sound of those, as they seem more 'liquid', for lack of a better term. Is the opto-isolator the main difference, or is it because it's feeding into the output tubes' bias?

[@PsionicAudio]

The brown panel amps like this Concert don't use a roach. Neither are they bias tremolo. A very involved circuit beyond the scope of a YT reply, but stay tuned. I'll explain it in a later video once I de-thump it.

[@chokkan7]

@@PsionicAudio ,
Thanks...I look forward to learning how it's done.

[@JudBarron]

Is this a 6G12-A? I have one and the vibrato channel sounds so good.
I think there is half a 12ax7 tube unused if I recall correctly?

[@PsionicAudio]

@@JudBarron Yes and yes. Great amp.

[@Tonetwisters]

They use the best system of tremolo (some say, "vibrato") that Fender ever used and are the exact opposite in complexity and quality from the roach system.

[@joesimon2018]

Jesus look at the output transformer. It's bigger than the power transformer.