Blackfacing a 69' Twin

Indigo_blues

Indigo_blues

New member
I'm going about blackfacing my 69' Twin at the moment.. we (my dad and I) took a look at the phase inverter circuit inside the amp again today but he scratched his head and said it didn't match the AA769 circuit that we had printed out.. we looked at the AB763 and it didn't match either.. turns out that its the AC568 configuration. So this amp was probably a very early 69' model, prob Jan or February from the numbers on the components..Fender at this time was mucking around with the design..

We've finished the re-cap job. Changed all the coupling caps. The power filter caps had already been changed last June when I first got the amp.

Maybe I'll post some pics later once the blackfacing is all done. :)
 
Those ol fellas tend to be a wee bit stuborn
Lots patients and petty conversation is essential !! :lol:

If you look at the basic fender design they are pretty much same ya but these amps tend to get tweaked by amp techs who give it their own twist and flavouring over the years.... keep a data while strip, rebuild to spec and tweak to taste if you are takin it futher !!

I have found extra transistors in a vintage tube amp....bladdy jokers !!

Keep wires short as possible my fren ...these fellas squeellll !!
 
yah i've been reading through the Fender forums extensively.. apparently during those CBS transition years, Fender would first do the modifications, then later they would come out with the schematic!! Talk about putting the cart before the horse! They were basically messing around with the old pre-CBS circuit... lead dress also apparently got abit touch-and-go later on as well.. this is why real blackface fenders still command a premium over the silverfaces..

well luckily an early silverface is pretty easy to blackface.. :) And they still sound pretty awesome. :)

will keep ya posted!
 
yah you're right... according to Fender afficionados, the tweed 59' bassman circuit is hailed as probably the all-time greatest ...
 
some updates.. the bias has been changed from balance bias to fixed bias. :)

We were contemplating whether to go the whole hog and change the plate load capacitors as well from 42k to 100k and 82k... My dad was hesitating but I think we'll probably do that too as changes are easily revertable. We've taken off the 2000pf bypass caps on the power tubes as well.

Will be firing the amp up later tonight.. keep fingers crossed!

The vibrato circuit was also examined(vibrato not working at the moment).. we found the problem.. turns out to be some corroded wiring near the photo diode.
 
Some pre-mod pics..

This is a shot of the chassis removed from the cab.
twinchassis.jpg


A closer look at the turret board.. you can see the bias pot and circuit on the top left hand corner of this pic.
twinturret1.jpg


Yikes! That cap is old! (the big fat brown one with the stain).. After removing those old caps, we tested them with a volt meter and actually they are all still in pretty good condition.. We can use them as backups.. :)
twincap2.jpg


More turret board shots.
twincap3.jpg


This is a shot of the photocell (vibrato circuit).. Its that black looking thingy in the middle.. its actually a rubber bung which acts as a light insulator for the photocell.. We pulled it apart to take a look inside..
twinphotodiode.jpg


Bonus shot of the transformers... freakin' heavy!!
twintransformers.jpg

Will post some more pics later..
 
please be carefull with the *photocell* ....
i believe its bulb and a Ldr coupled !!


Check all switches ...best replace...trust me on this one!!
Check all pots ....best replace !
i guess you know the rest !!

At least what you have there is pretty untouched ...what i had was a rats nest :roll:
 
Thanks again for the comments goose..

A shot taken last night.. we were trying to install the new photocell and neon bulb..
twindad.jpg


here's a closer shot..
twinpostmod.jpg


The new caps have been put in.. nice orange drops..

We bought a new neon bulb from simlim yesterday.. however the new bulb seemed to have a problem with the twin circuit.. not sure why it didn't flicker as it should have.. it didn't help even after we changed some resistor values.. finally we decided to leave it first.. i'll probably have to order a part from fender..
:roll:

We finally fired up the amp after that... everything worked great.. so I brought the amp home and played through it a little longer..

My report on the blackfacing is slightly mixed... the amp seems alot brighter.. it seems slightly louder with more touch sensitivity and 'spankier' and 'alive'... however there seemed to me a slight loss in bass response compared to when it was stock.. the overall sound is still great but the loss in bass troubled me abit...

I'll see if I can come to like the new sound.. honestly speaking I loved it when it was stock.. probably give it a bit of time.. if not maybe I'll just change it back to the previous configuration.. :)

We'll be coming back to the vibrato circuit once I get the part in.. to be continued..
 
I heard a black face bassman b4, compared to the silverfaced, its supposed to be lusher n thicker. Also warmer, tone to live for
 
Hey Cool Goose!! That's exactly the part we are looking for.. think we'll just order the old style one huh? More authentic.. it looks exactly like the one we took out.. :)
 
Hi edder, yeah that scope is a remnant from alot of his old equipment from the 70s and 80s.. he retired in the mid 90s.. but kept some of his essential equipment.. my house used to be filled with tubes when i was a small kid I remember.. my dad says he regrets throwing them all away.. 8O Think could have made a small fortune now if he had kept them.. most of them were RCA stuff he says..

:lol:
 
Hi wei, yah i read some reports that you have to actually change out the stock oxford speakers that came with the silverfaces to really achieve that blackface tone..

maybe later..
 
yeah actually if your dad is keen he might wanna service tube amps. There's always a demand for tube amp repairs and servicing.
 
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