Franchesca Schematic
Moderators: pompeiisneaks, Colossal
Franchesca Schematic
Here is a copy of the Kelly 90 schematic that I changed to match Franchesca. If your building an Express and want it to match the Franchesca pics this is what you need to use. If anyone sees any corrections needed just let me know.
[img1260]http://users.zoominternet.net/~jdhall/a ... evised.JPG[/img]
[img1260]http://users.zoominternet.net/~jdhall/a ... evised.JPG[/img]
Re: Franchesca Schematic
Thanks UR12!
Rockstah Amps: http://www.rockstahamps.com
Rockstah Amps Youtube: http://www.youtube.com/user/RockstahAmps
Builds and modification sound files: http://www.soundclick.com/rockstahplexitweaksandmods
Rockstah Amps Youtube: http://www.youtube.com/user/RockstahAmps
Builds and modification sound files: http://www.soundclick.com/rockstahplexitweaksandmods
Re: Franchesca Schematic
That is right on to Francesca as we saw it!
Allyn
Allyn
Re: Franchesca Schematic
NICE!
Thanks man!
Thanks man!
Re: Franchesca Schematic
Is the shield of the i/p cable connected to the plate instead of ground?
Re: Franchesca Schematic
Good point!!!! The shield on Franchesca is grounded at the input jack. I'll change the schematic. (Thanks!) The shield does go to b+ on the Liverpool but not the Express.stoo wrote:Is the shield of the i/p cable connected to the plate instead of ground?
update
Schematic changed!! Thanks again! Stoo
Re: Franchesca Schematic
You're very welcome. One more thing..those two 100K 3watt resistors in seies in the power supply....I think there was once two caps in series with a resistor across each one to balance the drop across each one. So couldn't a single resistor suffice now?
Stoo
Stoo
Re: Franchesca Schematic
Actually Franchesca doesn't use the two series caps in the power supply. It runs two 40uf caps wired in parallel for a total of 80uf. The two 100k resistors are actually bleeder resistors that bleed off the high voltage to ground after you turn the amp off.stoo wrote:You're very welcome. One more thing..those two 100K 3watt resistors in seies in the power supply....I think there was once two caps in series with a resistor across each one to balance the drop across each one. So couldn't a single resistor suffice now?
Stoo
- skyboltone
- Posts: 2287
- Joined: Wed May 10, 2006 7:02 pm
- Location: Sparks, NV, where nowhere looks like home.
Re: Franchesca Schematic
Hi Dana, I'm pretty new to the express lanes here. What are the diodes at the output plates for? Do they affect tone?
Thanks in advance
Dan
Thanks in advance
Dan
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Re: Franchesca Schematic
The diodes and the MOV are both used to protect the amp from Transient Spikes. Basically, Ken included these mods in his "Trainwreck pages" and he used them both in all of his Express amps. (I guess he didn't think the lowly EL84 was important enough to protect) If you were to get some high level spikes on you AC power line, this would also be passed through your power tranny and into your amp. The diodes protect mainly your tubes from being hit with these spikes and taking out your tubes. When you think about it most power in clubs and other venues have a lot of equipment connected to it that produces noise on a power line. Most older light dimmers are horrible and produce a lot of noise that sounds like a buzzing sound coming through your PA or amp. While these aren't considered Transient Spikes, I bring it up just as an example of how nasty with noise and spikes your AC power can be. Other things that produce spikes are light switches and and motors. They have nothing to do with tone.
Will the amp run without them? Yes It's just cheap insurance that you will probably never be needed but, if that 50 cents worth of diodes saves you one high dollar NOS EL34 being shorted out because of transient spikes then you come out ahead.
Will the amp run without them? Yes It's just cheap insurance that you will probably never be needed but, if that 50 cents worth of diodes saves you one high dollar NOS EL34 being shorted out because of transient spikes then you come out ahead.
Re: Franchesca Schematic
Seems a lot of people are confused regarding the varistor. I have redrawn the power switch to show it as being DPST and added the 130v varistor. Hope that helps.
-
- Posts: 2
- Joined: Wed Nov 21, 2007 4:20 am
transient spikes
MOV on the AC are to protect transients on the AC. The diodes on the tubes are to protect from transient spikes due to the inductance collapsing on the output tranny, usually occurs at high power output and hard attack I believe.
Re: transient spikes
This makes sense as to the diode usage. What would cause such a collapse? A broken voice coil? Blown preamp tube? Inadvertent speaker cable removal? Staccato? Abrupt drop of input signal? Open in speaker wiring? All of the above?guitbanger wrote:MOV on the AC are to protect transients on the AC. The diodes on the tubes are to protect from transient spikes due to the inductance collapsing on the output tranny, usually occurs at high power output and hard attack I believe.
- skyboltone
- Posts: 2287
- Joined: Wed May 10, 2006 7:02 pm
- Location: Sparks, NV, where nowhere looks like home.
Re: transient spikes
I left them both out. Just a rebel I guess.guitbanger wrote:MOV on the AC are to protect transients on the AC. The diodes on the tubes are to protect from transient spikes due to the inductance collapsing on the output tranny, usually occurs at high power output and hard attack I believe.
The Last of the World's Great Human Beings
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.
Seek immediate medical attention if you suddenly go either deaf or blind.
If you put the Federal Government in charge of the Sahara Desert, in five years time there would be a shortage of sand.