rooster wrote:gearhead - OK, I see what you are talking about and yes, I have read where many here are using this pwr supply cappage layout. But it is the Blue Guitar schematics that I am looking at mainly. They are just presented in a more organized way and - without that weird 470K resistor to ground that bridges the two 40uf caps. Is this KF designed? If he created this circuit, where did the Blue Gtr schematics come from with the 160uf caps? Which came first?
Somehow I can't help but wonder if somebody came along and recapped Francesca and Kelly and added this. Did they? Who here knows this?
Anyway, it really puzzles me to see this very odd 470K resistor network because as far as I understand such things, electrically it is not needed. (For a similar example, Fender used parallel caps in the '59 Bassman - and maybe one other Bassman model as well - and never used such a network.) Well, like I say, this really puzzles me. Is there some other amp manufacturer who used such a network in a similar application? If you could point me to that, I would love to see it.
And if it turns out that this particular resistive circuit is unique to a TW and that KF came up with it? Well, that would be very interesting.......
Anybody?
I can tell you and I am sure Allyn Meyers and Heebgb will confirm that Francesca's caps were original and untouched. If you pour over the pics and really study them you will see some of the foam rubber that was used to dampen vibration between the caps and the bottom of the chassis still on the caps.
Most of the problems with the schematics that came out prior to Francesca are because they were done by someone who was trying to draw a schematic from what they saw or what they think they saw. I can tell you that francesca has 2 40uf caps in parallel. Who ever drew the schematic showing 2 470k resistors with 2 caps in series probably decided that it "Looked" just like some of the fender amps that used higher values lower voltage caps in series to double the voltage and halve the capacitance. In a nutshell they either got it wrong or the amp that they were drawing the schematic from was like no other TW that anyone has ever seen. There are 2 100k resistors in Francesca that are in series to make a 200k resistor that is used as a bleeder resistor because the first two paralleled 40uf caps are before the standby switch and if you were to turn the amp off with the standby switch in the open position there would be no way for the caps to be discharged causing a safety hazzard for anyone working on the amp. In other amps like the liverpools Ken used 1 470k resistor as a bleeder resistor instead of the 2 series 100ks. Why? I don't know, but that is the way it is and if the schematics don't reflect that then they are wrong.
Having said all of that, I think we have to give these guys a lot of credit as 99% of what they drew was correct. We wouldn't be where we are now if it hadn't been for some of these guys who did the best they could with what they had to work with. If you have ever tried to draw a schematic from looking at the inside of an amp is is not easy. Then complicate that with the problem that you aren't going to be allowed to remove anything like the preamp board so you can see exactly where and how everything is wired. If you cant take it apart you have to make asumptions and sometimes your assumptions are going to be wrong.
So to conclude, The Blue guitar schematic is wrong if you are comparing it to Francesca. There is a corrected Francesca schematic in the files section that has evolved and has all of the mistakes corrected to reflect exactly what you will find in francesca. Ken basically used what he had on hand or could get his hands on. If he needed a 200k resistor and didn't have one then he used 2 100ks in series that he did have on hand.
Just my 2 cents
