Blackfacing a '68 or '69 Silverface

[toneman335]

Just curious from a non-technical point of view...when blackfacing a '68 or '69 silverface does that just include just resistor values at some points? I guess I am wondering do the transformers or anything else needs to be changed?
My understanding is that as the amps went later into the 70's the amps were quite different such as the transformers.

[TheAmpNerd]

Some were and some weren't.

AND

Some of the silverface amps in those years
had the blacface circuit in them.

Depending on the amp.

Check them all out at the Fender Field Guide, the
link provided here:

http://www.ampwares.com/ffg/index.html

[gldtp99]

Nothing wrong with early SF amps in orig configuration---- depending on model, as already stated-----using hi quality tubes and speakers would likely yield better real world results than "blackfacing" circuit revisions---- i know "blackfacing" SF amps is a popular idea but with many early SF amps , it's probably a waste of time.
Check out some Brownface era Fender amps for some interesting tones---- local players have been preferring my orig Fender Brownface amps and clones over my Blackface Fenders in demo tests lately--- a somewhat thicker, rounder tone and the Trems are killer...............gldtp99

[TheAmpNerd]

I agree with goldtop. Especially since it is 103 degrees here in Tejas
and too damn hot to do anything else.

:drool

[Old Tele man]

...look very, VERY closely at the schematics between the amp models that first used GZ34 rectiifers and then later (circa 1968) switched to 5U4GB rectifiers...notice any difference in the PT voltages? (ie: from 360VAC to 365VAC) ...but, notice there's no mention what-so-ever of change in the PT partnumbers!

...why's this important? Two subtle reasons: (a) different filament current requirements; and (b) different rectifier "diode-line" voltage drops (ie: "sag" voltage under load)...but, the SAME PT p/n's are used before/after the changes!

...obviously, something "changed" without getting documented on the schematics very well.

[tremolux]

Your right, and I remember noticing that in the 5U4BG schematics years ago when the first Fender schemo book came out (the orig copies out of the service bench guides) and thinking.....well, if the recto and the voltages on the schemo changed, then how could they still be using the same exact winding specs re:the PT? (Overall B+ went up in most early SF amps, but was that atributed to increases in the wall levels around the same time frame, but was never indicated on the schematics?)