Yet ANOTHER aspect of the SF era worth noting was Fender’s use of paraffin to treat the (fiberboard) component boards in an effort to prevent warping and cracking, resulting from prolonged heat and/or moisture exposure, and possible contamination which could result from a brittle, dried out board that may have absorbed moisture tainted with rust/oxidation, or possibly a spilled beverage, etc.
Initially this may have seemed like a good idea, but unfortunately what happened as a result was the paraffin would melt from the heat of the tubes during operation, and over time would tend to collect in the preamp tube sockets, as well as on the basses & pins of the preamp tubes themselves. Here is where I will sometimes need to spent extra detailing time, removing all of the excess paraffin from the boards, sockets, and tubes.
[NOTE: As a part of my maintenance procedure with older amps (Fenders and otherwise), I will treat the boards with a solution which is completely absorbed by the board (and will not “melt away” when exposed to heat), restoring pliability to an otherwise brittle fiberboard, as well as improving its non-conductive/insulation characteristics. The board will also now be resistant to any moisture, avoiding the possibility of absorbing what could be tainted in some way.]
As the amp is being re-built and re-assembled, with much more attention being paid to lead placement and layout than Fender ever did during the CBS era, there are the other well-known upgrades such as changing some of the smaller value ceramic capacitors [such as the signal caps in line with the Treble control(s), to and from the reverb network, and at the input to the phase inverter] to Silver Mica capacitors, which will result in what most players interpret as a “sweeter” high-end response (this is often done to BF and “tweed” era Fenders as well, since ceramic composite caps were also used in those eras). In most cases, I will also re-do the “heater” line wiring, with tighter winding to assist in minimizing hum.
Upon completion of this process (which will usually take anywhere from 12 to18 hours, depending on the condition/model of the amp), I can now remove the previously mentioned high frequency shunt .002µF caps at the power tube control grids, since the “tighter” construction and removal of the “pull-out” functions has eliminated the potential parasitic oscillations.
NOW what we have is what I (and a number of happy clients who have had this done) would consider a TRUE “Blackfacing” of a SF Fender, MUCH closer to that of a “real” BF than merely changing a handful of capacitors and resistors (not to mention a cleaning and maintenance overhaul in the process). It is now an amp that far exceeds what the amp originally was, with much improved dynamics and “touch sensitivity”.
In my experience, the commonplace procedure of “Blackfacing” the later “Silverface” era Fender classic models of the later 60’s and 70’s, when performed by most shops (as well as the many DIYers that prevail these days), usually consists of changing a handful of capacitor & resistor values, re-configuring the bias network for voltage adjustment (as opposed to the “balance” configuration found in most SF models, and even some of the later BF models), and removing the R/C components of the power amp cathode network found in the ’68 models. Also worth mentioning would be the removal of the infamous “pull-out” master volume ckt., which is [for the most part] universally disliked, by even the least critical of players. And [last but not least] the “pull-out” boost volume controls, found on some Deluxe Reverbs, which often resulted in a less than pleasing “nasal” toned sound.
“On Paper” this may appear to replicate the more sought after circuits of the BF era amps, but there is one important detail that is being overlooked. That being “clean” workmanship, whereas the “integrity” of construction is haphazard at best (if not just plain sloppy) on all except perhaps the very earliest of SF Fenders when compared to the construction of an “authentic” BF (or earlier) era Fender. Here it is important to note that in many cases, this more haphazard construction (in addition to the “add-on” circuitry of the previously mentioned “pull-out” functions) would frequently result in what is referred to as parasitic oscillations (an ultra-sonic frequency oscillation, that “rides” on the guitar/instrument signal, resulting in some NASTY interference/overtones). Fender’s way of “fixing” this issue was to put a .002µF ceramic disc capacitor at the power tube control grids going to ground, thus shorting the high frequency of the oscillation out of the signal path, along with a lot of desired harmonic content of the instrument signal.
When I perform a “Blackfacing” procedure to one of the aforementioned models, I will proceed to remove virtually all of the original wiring (usually with the exception of the wiring between the main component board and the preamp tube sockets, since this was one part of the assembly that was often done up to the standards of the earlier years). I will also remove the soldering of the brass front panel grounding plane from the chassis, where all of the front panel controls are mounted (with the exception of master volumes on those models that had them). There was also some power supply grounding patterns that also differed from the BF era supply grounds, which I will also re-do accordingly.
Another characteristic common to the SF’s was a grounded [at each end] wire, that was wound around the cluster of power supply leads coming from the filter pack on the underside of the chassis, and the group of wires of each channel running between the “tone stack” capacitors on the main board, and the front panel controls. I can only assume that this was supposed to simulate a shielding like effect. Here I will again replicate what was done on the earlier amps, which was to wind the supply/tone leads together, re-“laying” them in a much tighter layout, and eliminate the previous grounded wire.