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Question about blackfacing a SF Deluxe

jompa

Member
Messages
58
I recently picked up a SF Deluxe. Seller claimed it was a '76, but the serial shows it as a '77--no master volume on the front. The guy I bought it from took it to a tech who he claims "did a bunch of stuff to make it sound better." Basically, I'm not sure what's been done, and I haven't even dug into the guts yet. Honestly, although I've read a bunch about amps, I'm not experienced enough yet to know my way around the chassis. :dunno

So here's my question. I recall reading somewhere that in the late 70s, some Deluxes started to get different power trannies than the earlier SFs. If this is the case, then they can't be truly blackfaced. Does anyone know if this is true? The standard schematic for AB868 SF Deluxes is the same for '68-82 with no indication of differently spec'd PTs. Also, I'm not really sure what's been done to this amp. According to Weber, codes show both transformers as Woodward-Schumachers--606.

Is there any way to tell if this amp can be BF'd with this power tranny? Has anyone else read or heard about this? I'd appreciate any info I can get. Thanks in advance.
 

SatelliteAmps

Member
Messages
6,186
It can be, but the bigger question is why? Those amps sound awesome as is. My personal Deluxe Reverb is a 1976, and it sounds better than any of the Blackfaces I've owned.

Does the amp not sound good? Or is there some other reason to try and make it into a Blackface version?
 

JJman

Member
Messages
992
The "....different power trannies...." issue does not apply to the Deluxe. That issue involves the change to the "Ultra-linear" output but that was only done to the larger models.

If the speaker is original, that might be the only item to seriously consider replacing. Or not.
 

hasserl

Member
Messages
4,711
There's really not much of a difference between the bf and sf models. The sf uses a 5U4GB rectifier. Interesting that the schematic shows the same voltages for both, even though the 5U4GB will produce lower voltage, so either the power transformers were changed to a higher voltage, or the amps operated at lower voltage. But the schematic shows the same 330VAC voltage on the PT secondary on both schematics with the same 420VDC B+.

Other than that, the only difference I see is the PI input cap is changed from .001uf on the bf to .01 on the sf. Other changes were to the wiring & lead dress, changes in cap types, and changes in cab construction.
 

Swarty

Member
Messages
1,130
There were also periods that received the .002uF caps (tan/orange ceramic discs) on the output grids and reverb return. I'd leave the one on the reverb, but the ones on the output tubes can be snipped and the top end will open up nicely.
 

jompa

Member
Messages
58
It can be, but the bigger question is why? Those amps sound awesome as is. My personal Deluxe Reverb is a 1976, and it sounds better than any of the Blackfaces I've owned.

Does the amp not sound good? Or is there some other reason to try and make it into a Blackface version?
It actually sounds very good. I don't subscribe to BF vs SF amp snobbery, but I mostly would like to use it as my first amp mod project in order to try my hand as a solder slinger. I'm definitely going to replace the Oxford, and I'm considering choices. Just overall prepping and gathering info 'cuz I've got a couple of guitars on the bench right now.

Thanks to the rest of you for the info. I'll probably just give it a thorough once over and then follow what my ears tell me from there. Good to know I don't have to mess with the PT.
 

smolder

Platinum Supporting Member
Messages
14,319
the 'did a bunch of stuff to make it sound better' would concern me. Find a pic of an original chassis online and compare to see what was done. If all he did was swap out some capacitors... its probably easily reversible, or it may indeed sound better as a result. Stock is not always best... but I have heard stories about serious butcher-ings.
 




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